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08:30-10:00 Session 13: The application of menthol in sport, exercise and occupational settings: to apply, ingest or discard?
Mechanisms through which menthol acts on human temperature regulation and perception, and possible effects on muscle function
PRESENTER: Jason Gillis

ABSTRACT. Menthol is one of the world’s most widely used flavors and fragrances, and owing to its cooling and analgesic properties, it has long been used to alleviate symptoms arising from a number of maladies, from the common cold to musculoskeletal pain. More recently, menthol has been used as an ergogenic aid to alter perception and performance, and as part of an approach for studying the physical basis of temperature sensation and thermoregulatory function in humans. The purpose of this opening presentation is first to review the mechanisms whereby menthol is thought to exert its influence, and second, to explore its influence on muscle function per se. Specifically, Part One of this presentation will explore possible mechanisms through which menthol acts on human temperature regulation and perception. This will include an overview of what menthol is, and common uses. A more general review of the physical basis of human thermosensitivity will follow, with emphasis on the family of temperature-activated Transient Receptor Potential (TRP) ion channels, focusing on the TRP Melastatin 8 (TRPM8) ion channel and its interaction with menthol in primary sensory neurons. The afferent pathways and central sites of integration arising from menthol exposure will be reviewed, along with the associated perceptual and thermophysiological responses. Various factors thought to influence menthol’s forcing function when taken orally or topically will also be presented. Part Two of this presentation will explore the possible influence menthol exerts on muscle function when applied topically. Specifically, menthol’s possible influence on recovery of muscle soreness and gross measures of physical performance following exercise-induced muscle will be reviewed, along with its acute influence on muscular strength, power, and joint range of motion. Attendees will be given a comprehensive overview of current research in this area, as well as gaps in our knowledge, and directions for future studies.

The effectiveness of orally applied L-menthol on exercise performance in the heat
PRESENTER: Owen Jeffries

ABSTRACT. During exercise in the heat, increasing thermal load leads to thermo-behavioral adjustments in exercise performance, due to greater perceptual and physiological strain. Behavioral reductions in exercise intensity in the heat are initially mediated via rises in skin temperature, which alter thermal perception (comfort and sensation) and later by rises in core temperature, which increase cardiovascular strain and perceived exertion. Therefore, thermoregulation may be ordered and dependant on the magnitude, timing and/or prioritisation of afferent signals. Non-thermal cooling via L-menthol has been shown to enhance exercise performance in the early and latter stages when delivered orally at a concentration of 0.01%. Indeed, during periods of progressive thermal stress, imposed by the combination of maximal exercise and environmental heat and humidity, L-menthol has been shown to offer an immediate cooling stimulus thus extending exercise capacity. However, repeated administration of L-menthol during exercise in the heat, as thermal load increases, is unable to recover a decline in work rate. Therefore, it is unclear whether the potency of L-menthol is sustained upon frequent application and what strategies are needed in both sporting and occupational settings to optimise its effectiveness. In this part of the symposium we will consider oral delivery of L-menthol and its potential for reducing an individual’s perception of heat stress with associated effects on exercise tolerance in the heat. We will also examine the frequency of use, optimal concentration, timing and novelty of L-menthol in a sporting and occupational context.

The effects of single and repeated applications of menthol to the skin on endurance exercise performance in the heat
PRESENTER: Martin Barwood

ABSTRACT. Endurance exercise performance frequently takes place in conditions that pose an increased risk of heat illness. For example, the next Olympic games is set to be staged in Tokyo, Japan, and will take place in high ambient temperatures combined with a high relative humidity thereby minimising viable avenues for heat loss. Accordingly, exercise performance is likely to be impaired through multifaceted mechanisms. One early contributor to the slowing exercise pace is the sensation of becoming hot and uncomfortable caused by hot skin temperatures although elite athletes are accustomed to ignoring these sensations thereby increasing their risk of heat related collapse. The topical application of menthol to the skin may assist in facilitating the uncoupling of thermal state from perceptual state by stimulation of TRPM-8 thermoreceptor thereby stimulating cool sensations and alleviating thermal discomfort in a manner similar to temperature reduction itself. At low concentrations of sprayed Menthol (0.05% concentration) it has been noted that this altered thermal perception is not matched with any (measurable) change in thermoeffector response. At higher concentrations, it has been noted that topical menthol application impairs some heat defence mechanisms (i.e. vasoconstriction) and altered sweating thereby increasing the risk of heat illness whilst relieving thermal discomfort. This part of the symposium explores the extant literature on single and repeated topical applications of menthol to the skin with a view to describing the performance and thermoregulatory consequences of menthol use during sport. We will also consider the research evidence for menthol use in the occupational setting although little is known about the latter. This section of the symposium will conclude with an appraisal of the risk of heat illness that could be caused by menthol application, practical considerations of the application modality and future directions for menthol use in the sporting and occupational setting.

Oral application of L-menthol in the heat: from pleasure to performance

ABSTRACT. When menthol is applied to the oral cavity it presents with a familiar refreshing sensation and cooling mint flavour. This may be deemed hedonic in some individuals, but may cause irritation in others. This variation in response is likely dependent upon trigeminal sensitivity toward cold stimuli, suggesting a need for a menthol solution that can be easily personalised. Menthol’s characteristics can also be enhanced by matching colour to qualitative outcomes; a factor which can easily be manipulated by practitioners working in athletic or occupational settings to potentially enhance intervention efficacy. This presentation will outline the efficacy of oral menthol application for improving time trial performance to date, either via swilling or via co-ingestion with other cooling strategies, with an emphasis upon how menthol can be applied in ecologically valid scenarios. Situations in which performance is not expected to be enhanced will also be discussed. An updated model by which menthol may prove hedonic, satiate thirst and affect ventilation will also be presented, with the potential performance implications of these findings discussed and modelled. Qualitative reflections from athletes that have implemented menthol mouth swilling in competition, training and maximal exercise will also be included.

10:30-12:00 Session 14: Physiology
Influence of core body temperature-mediated changes in cerebral blood flow regulation during exercise

ABSTRACT. Introduction: Cerebral blood flow (CBF) decreases by approximately 10-15% for every 1°C rise in esophageal temperature (Tcore) during passive heat stress. Acute moderate-intensity exercise (e.g., 30-45 mins at 50-60% workload max) also increases Tcore (+0.7-0.8°C); however, likely due to small elevations in arterial PCO2 and metabolism, such exercise increases CBF (+10-20%). This study aimed to isolate the role of Tcore from PCO2 on CBF regulation during submaximal cycling exercise.

Methods: Healthy adults (n=8 completed; 25±4 yrs) participated in two separate interventions: 1) 45 mins semi-recumbent cycling (EX; 50% workload max); and 2) 45 mins passive heat stress (HS; 49°C water-perfused suit) to match the exercise-induced increases in Tcore. Blood flow in the internal and external carotid (ICA and ECA, respectively) and vertebral (VA) arteries (Duplex ultrasound) was measured. End-tidal PCO2 and PO2 were “clamped” to resting values within each condition.

Results: The changes in Tcore with EX and HS were matched between conditions (Δ0.77±0.28°C, P=0.91). Chest skin temperature was higher during the HS intervention (HS: Δ2.96±1.30°C vs. EX: Δ0.40±1.25°C, respectively, P<0.01); whereas, increases in cheek temperature (Δ1.75±1.06°C) were not different between conditions (P=0.66). Related to this, although ECA blood flow increased during both EX and HS for thermoregulatory heat dissipation (EX: Δ37±46% vs. HS: Δ54±32%, time effect: P<0.01), there was no difference between conditions (P>0.05).

Blood flow in the ICA was unchanged with EX and HS interventions (P=0.71), consistent with the unchanged end-tidal PCO2 (P=0.42); whereas, VA blood flow was higher throughout both EX and HS (EX: Δ21±24% vs. HS: Δ20±25%, time effect: P<0.01) with no between condition differences. Global CBF was unchanged with either intervention (P=0.87). Including blood pressure as a covariate did not influence these CBF findings (P>0.05).

Conclusions: These data indicate a selective temperature-dependent influence mediating elevation in posterior CBF during exercise that is independent of PCO2.

Effect of local lower limb heating on cardiovascular hemodynamics, core temperature, and perceptual measures in young healthy men and women.

ABSTRACT. Introduction: Passive heating may improve cardiovascular health in humans; however, whole-body protocols are not well-tolerated. Local heating protocols may be more feasible, enjoyable alternatives; but their efficacy for eliciting a sufficient cardiovascular response – defined here as achieving HR in the moderate intensity range for exercise (55-69% HRmax) – has not been well-established. Method: Ten young, healthy males and females underwent two 45-minute leg heating protocols at 45 °C, with water level either up to the ankles or knees. Cardiovascular hemodynamics were measured using finger photoplethysmography. Core (Tcore) and skin temperatures (Tsk) were measured using telemetric pills and temperature probes, respectively. Perceptual measurements were assessed using general feeling, thermal comfort and sensation scales. Measures were taken pre- and post-intervention. Results: Tcore (PRE: 37.1±0.1 vs. POST: 37.6±0.2 °C, P<0.05) and foot Tsk (PRE: 28.3±0.9 vs. POST: 43.1±0.4 °C, P<0.05) increased post-intervention regardless of condition. Calf, thigh, and arm Tsk increased over time within each condition, but was greater after 45-minutes in the KNEE condition. Chest Tsk increased over time within each condition. CO and HR increased post-intervention to the same extent with both conditions (CO: PRE: 5.2±1.4 vs. POST: 6.5±1.5 L/min, P<0.05; HR: PRE: 57±9 vs. POST: 76±9 bpm, P<0.05). HR post-heating was 39% of the age-predicted HRmax. Regardless of condition, affect decreased (PRE: 2.1±1.4 vs. POST: 0.1±2.5, P<0.05), and thermal comfort (PRE: 0.1±1.1 vs. POST: 2.7±1.6, P<0.05) and sensation (PRE: 3.8±1.3 vs. POST: 7.4±1.3, P<0.05) increased post-intervention. Conclusions: While Tsk changes were more pronounced in the KNEE condition, both conditions created similar but insufficient cardiovascular stress demonstrated through changes in Tcore, HR, and CO. Participants rated general feeling, thermal comfort and sensation similarly between conditions over time, suggesting that the two protocols may be used interchangeably. Future studies should explore whether novel vascular outcomes change in response to either local heating protocol.

Interactions between morning light conditions, body temperature, thermal comfort, and reaction time

ABSTRACT. Introduction: In earlier well controlled laboratory studies we showed that light conditions can affect thermal physiological parameters and that thermal discomfort can partly be alleviated by specific lighting conditions. Here we study whether light conditions can counteract the reduction in thermal comfort and alertness in a warm environment.

Method: Sixteen healthy females participated in a randomised crossover laboratory study, consisting of three overnight sessions per participant. Participants stayed in the respiration chambers and were allowed to sleep for 6.5 hours only in order to induce sleepiness. In the subsequent morning one of three different light conditions was offered in a warm environment (29°C), as to evaluate the effect of two illuminance levels (50 lux and 500 lux, both with a correlated colour temperature (CCT) of 2000 K) and two CCT’s (2000 K and 6500 K, both with an illuminance of 500 lux). Outcome parameters were: alertness, thermal comfort, body temperatures, melatonin and cortisol levels.

Results: There were large inter-individual differences in visual comfort and thermal comfort. Visual and thermal comfort were significantly correlated. Interestingly, thermal comfort levels are higher in light conditions that are perceived as visually more comfortable. In addition, participants had shorter reaction times under low CCT light as compared to high CCT light. Subjective sleepiness did not differ between light sessions. Under 2000K light, core body temperature was significantly higher than under 6500K light.

Conclusions: Light conditions that improve performance do not necessarily yield a better visual and thermal comfort. Thermal comfort is higher in light conditions that are perceived as visually more comfortable. Altogether, the study shows that light conditions have the potential to affect thermal physiology, thermal comfort and reaction times. In practise individual preferences in light conditions need to be taken into account to enhance thermal comfort.

Application of an adjusted neurophysiological (foot) skin blood flow model to a real life case study

ABSTRACT. Introduction: The neurophysiological skin blood flow (SBF) model [1] advanced the prediction quality of thermo-physiological models. However, it was developed for low activity levels (0.8 met). A field case study [2,3] showed that for walking (2.8 met), the predicted foot skin temperature (T_(skin,foot)) was underestimated by up to 10°C. One reason for this result was a low simulated SBF at the feet. In a follow-up study, SBF and skin temperatures were investigated in 15 subjects performing light to medium activities under laboratory conditions to develop an adjusted foot SBF model. Here, the model is applied to the case study to investigate the effect of field conditions.

Method: The case study included local skin temperature measurements of 5 human subjects while freely walking indoors (2.8 met) for one hour. The subjects wore three everyday outfits of 0.5, 0.8 and 1.1 clo [4]. The three scenarios are simulated in the thermoregulation model ThermoSEM [1], firstly, using the (standard) neurophysiological approach, and secondly, using the adjusted foot SBF model. For both cases, ΔT_(skin,foot) is calculated as the difference between simulated and measured data averaged over the last 15 minutes of the experiments.

Results: The application of the adjusted foot SBF model improved the average ΔT_(skin,foot) from -6 – -11°C to 0.4 – 2°C. Hence, the average results are closer to an acceptable range for skin temperature prediction of the extremities. However, in some individual cases, the simulation is now overestimating T_(skin,foot). This finding might be due to low control of actual walking speed and walking type (e.g. climbing stairs) of the subjects in a field setting, as well as variations in building local climate.

Conclusions: The advanced foot SBF model improves the skin temperature prediction of ThermoSEM for walking scenarios at medium speed for the case study. Further investigations should include a larger number of subjects which might perform also at higher walking speeds and different activities.

References: [1] B.R.M. Kingma, M.J. Vosselman, A.J.H. Frijns, A. a. Van Steenhoven, W.D. van Marken Lichtenbelt, Incorporating neurophysiological concepts in mathematical thermoregulation models, Int. J. Biometeorol. 58 (2014) 87–99. [2] S. Veselá, B.R.M. Kingma, A.J.H. Frijns, Taking Thermal Regulation Models From the Lab To the World: Are Current Views Ready for the Challenge?, in: M.G.L.C. Loomans, M. te Kulve (Eds.), Heal. Build. Eur. 2015, Eindhoven, 2015. [3] S. Veselá, B.R.M. Kingma, A.J.H. Frijns, Effects of sweating on distal skin temperature prediction during walking, Extrem. Physiol. Med. 4 (2015) A31. [4] J. Lee, H. Zhang, E. Arens, Typical Clothing Ensemble Insulation Levels for Sixteen Body Parts, in: CLIMA Conf. 2013, 2013: pp. 1–9.

Effects of different duration of voluntary hypocapnic hyperventilation on physiological responses during and following supramaximal exercise
PRESENTER: Kohei Dobashi

ABSTRACT. Introduction: Voluntary hyperventilation increases carbon dioxide (CO2) elimination, reducing arterial CO2 pressure (hypocapnia). We have recently shown that pre-exercise voluntary hypocapnic hyperventilation reduces aerobic metabolic rate with a compensatory increase in anaerobic metabolic rate and an attenuated tachycardia response in comparison to spontaneous breathing condition without impairing exercise performance during the 30-s Wingate anaerobic test and 30-s high-intensity intermittent cycling exercise. To develop hypocapnia, a long-duration (e.g., 20 min) voluntary hyperventilation was typically employed in previous work. However, it is unclear whether shorter voluntary hyperventilation differentially modulate the aforementioned physiological responses in comparison to a longer one. Method: Ten healthy young males performed a 60-s supramaximal cycling (120% peak oxygen uptake) that was preceded by either: 1) spontaneous breathing (control), 2) 5-min or 3) 20-min pre-exercise voluntary hyperventilation (30 L min-1 of ventilation). Respiratory gases, arterial blood pressure, and heart rate (HR) were assessed throughout. Results: Both 5-min and 20-min hyperventilation decreased end-tidal CO2 pressure to ~24 mmHg, whereas it was maintained at normocapnic level of 35 mmHg in the control trial, prior to the supramaximal exercise. Oxygen uptake during the supramaximal exercise was similarly reduced by the two hyperventilation trials in comparison to the control trial. HR during and following supramaximal exercise was lower in the 20-min hyperventilation trial than the control trial, whereas it was similar between the control and 5-min hyperventilation trials. Conclusions: Our results suggest that 5-min and 20-min pre-exercise voluntary hypocapnic hyperventilation similarly reduce aerobic metabolic rate during 60-s supramaximal exercise, and that only the 20-min hyperventilation lowers HR during and following supramaximal exercise. Regarding practical application, pre-exercise voluntary hyperventilation during high-intensity exercise may be a useful strategy to stress and thus improve anaerobic energy system, and shorter duration of hyperventilation (e.g., 5 min) is sufficient to provide this effect.

Cutaneous Activation of TRPM8 Receptors Does Not Mediate Cross Dermatome Changes in Blood Flow

ABSTRACT. Introduction: Topical menthol-based analgesics induce an increase in skin blood flow (SkBF) through TRPM8 receptor-dependent activation of sensory nerves and endothelium-derived hyperpolarization factors. It is unclear if menthol-induced TRPM8 activation mediates a reflex change in cutaneous blood flow across the dermatome. The purpose of this study was to determine the effects of localized menthol application on SkBF across a common dermatome. We hypothesized that SkBF would be increased with menthol at the site of application and the contralateral dermatome through a spinal reflex mechanism. Method: In a double blind, placebo controlled, cross-over design, 11 healthy participants (5 men; age=22±1yrs) were treated with direct application of 5% menthol gel (Biofreeze™) or vehicle control on the L4 dermatome. Red blood cell flux was measured using laser Doppler flowmetry over the area of application, on the contralateral leg, and in a separate dermatome (S1) to serve as control. Cutaneous vascular conductance was calculated for each measurement site (CVC=flux/MAP). Thermal sensation was measured every 10 minutes. Results: Menthol elicited lower thermal sensation at all time points, compared to the vehicle control (p<0.05). At baseline there were no differences in CVC between menthol and vehicle control (VC) gels, or among sites (all p>0.05). After 30 minutes, CVC increased in the site treated with menthol but not the VC (110±24, vs. 12±4 flux*mmHg-1, p<0.001). There was no effect on the contralateral dermatome to either treatments (16±6 vs. 7±2 flux*mmHg-1, p>0.05), or on the S1 dermatome (9±7 flux*mmHg-1, p>0.05). Conclusions: A menthol containing topical analgesic increased SkBF over the area of direct application, but had no effect on the untreated contralateral dermatome. These data suggest that menthol-induced activation of the TRPM8 receptor does not mediate a spinal reflex to increase SkBF across the area of common innervation. Funding provided by Performance Health

Sustained Skin Erythema and Blood Flow Responses to Acute Ultraviolet Radiation Exposure

ABSTRACT. Introduction: Acute exposure to ultraviolet (UV)-B light elicits an inflammatory response in the skin, resulting in erythema (reddening) and increased skin blood flow that lasts at least 24 hours. However, the acute time course (i.e., initial eight hours) of each of these responses is unclear. Likewise, it is unknown whether these responses differ following exposure to broad spectrum (UV-A/B) light compared to UV-B alone. The purpose of the current study was to investigate whether temporal differences exist in skin blood flow and erythema responses and whether there are differences between acute UV-B and UV-A/B exposure. We hypothesized that (1) the erythema and blood flow responses would track each other, and (2) both responses would be higher following UV-A/B compared to UV-B exposure. Methods: The ventral aspect of both forearms of 14 healthy young adults (7M/7F) were exposed to either UV-A/B (750 mJ/cm2; 450 mJ/cm2 UV-A + 300 mJ/cm2 UV-B) or UV-B (300 mJ/cm2) alone. Erythema index (EI; reflectance spectrometry) and red cell flux (laser-Doppler flowmetry) were measured before, immediately after, and 2, 4, 6, and 8 h post-exposure. Cutaneous vascular conductance was calculated (CVC=flux/MAP) at each time point and both EI and CVC were expressed as change from baseline. Results: EI increased linearly after exposure to UV-B (p<0.01 at 4, 6, and 8 h post-exposure) and UV-A/B (p<0.05 at 4, 6, and 8 h post-exposure). CVC did not increase above baseline until 6 h post-UV-B (p=0.04) or UV-A/B (p<0.01). There were no differences between UV-B and UV-A/B-induced responses in CVC or EI (all p>0.05). Conclusions: Exposure to UV-B or UV-A/B induced an immediate and linear increase in EI, but a delayed increase in CVC. These responses were similar between UV exposures, suggesting that the blood flow and erythema responses to acute UV-exposure are primarily driven by UV-B radiation.

13:00-14:30 Session 15: Thermal modeling and soldier load
Toe and boot temperatures during Canadian Armed Forces operations in the Arctic: Challenges of establishing accurate field data

ABSTRACT. Abstract:Canadian Armed Forces soldiers train in some of the harshest conditions on Earth, including the extreme cold of the Canadian Arctic. Without proper protective equipment and training, these soldiers are particularly at risk of developing cold weather injuries (CWIs) especially in their hands, feet, and face. However, much work remains to establish the best individual thermal protection to prevent CWIs during operations in the Arctic. Method:20 soldiers were recruited during a 5-day Arctic military exercise in 2018 and 2019. Operations involved sleeping in Arctic tents, fishing, snowmobile, and long patrols on foot. Boot (Tboot) and toe temperatures (Ttoe) were collected continuously using an iButton placed on the boot liner and a skin thermistors placed on the big toe, respectively. Statistics were conducted on measurements during outside operations 1) to quantify individual ranges in Tboot and Ttoe and, 2) to establish the relationship between ambient temperature (Tamb), Tboot and Ttoe. Results:Complete Tboot and Ttoe data was obtained from 10 males over the 5 operational days with 4 to 10.5h spent outside at Tamb ranging from -30 to -40C (without windchill). No CWIs on the feet were reported in these individuals. Results indicated that Tboot and Ttoes did not change significantly Day 1 to 5 (ANOVA; p=0.18 and p=0.28, respectively). Tboot averaged 4.0±1.2C (min -6.0±1.1C and max 19.3±2.0C) and Ttoe averaged 22.0±1.4C (min 14.2±1.7C and max 31.1±0.5C). Importantly, no significant correlations were found between Tboot, Ttoes and Tamb (Pearson; r2=0.76 p=0.13, r2=0.60 p=0.31 and r2=0.58 p=0.31). Conclusion: Results from this study indicate that although military personnel face temperatures that could results in CWIs, some individuals’ foot temperatures are well controlled, independently of changes in environmental conditions. Most importantly, this study highlights the challenges researchers face when attempting to collect multi-day field thermal data in soldiers to obtain a reliable model for temperature management.

Optimization of Readiness in Extreme Cold: A Tool For Risk Evaluation and Mitigation

ABSTRACT. Introduction: Cold stress degrades physical performance, results in casualties, and ultimately impacts military operation. Proper selection of cold weather ensembles is the primary mitigation strategy for preventing cold injury. However, the selection of cold weather ensembles are currently often based on experiences or very simple charts/tables, and do not reflect the complicated requirements of cold protection. Purpose: Define the thermal performance of cold weather ensembles using human-centric metrics (i.e., physiological criteria or safety limits), and develop a cold weather ensemble decision aid (CoWEDA) to predict frostbite and hypothermia risks, and excessive sweating. Methods: Thermal performance is defined by endurance times, which are the durations before the physiological safety limits, corresponding to the onset of frostbite, hypothermia or skin wettedness, are reached. A database of thermal properties of individual clothing items was established. Algorithms were developed to predict thermal properties of multi-layer clothing configurations. The metrics of ensemble thermal performance, clothing database, algorithms and the validated six-cylinder thermoregulatory model were integrated into CoWEDA. Results: CoWEDA is user-friendly and guides selection of the most appropriate cold weather ensemble(s) relative to anticipated activities and environmental conditions. CoWEDA allows users to build their own ensembles from the clothing inventory by body regions, and then interprets their selection in the context of safe operation times and cold injury risks. Comparisons with measured skin temperatures during exposure to 0 to -40°C environments shows that CoWEDA predictions are acceptable. Conclusion: CoWEDA is the state-of-the-art tool for cold readiness optimization, mission planning, clothing selection, risk awareness, and cold injury prevention. Disclaimer: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Motor-cognitive performance in the heat – influence of hydration, radiation and heat acclimation

ABSTRACT. Introduction: In a warming world, the occurrence and duration of heat waves will increase and for effective analyses (including modelling and proposed mitigation methods), it is important to evaluate the effects of heat stress on performance and productivity. In this presentation, the effect of hyperthermia on combined cognitive and motor performance and confounding effects of dehydration, solar-radiation and heat acclimation will be covered and contextualized to occupational settings.

Methods: Applying a comprehensive test battery with separate and combined motor-cognitive tasks, we have explored the effects of: 1) moderate [1°C] and severe hyperthermia [≥2°C], 2) dehydrations [2% loss in body mass], 3) solar radiation [500 W/m2 applied to the head or lower-body] and 4) prolonged heat acclimation.

Results: For euhydrated participants exposed to dry heat (low/no solar radiation) a moderate core temperature elevation can be tolerated without impairing cognitively dominated tasks or motor performance. However, severe hyperthermia profoundly reduces complex motor task performance and this effect is markedly aggravated if moderate dehydration is superimposed. In addition, with combined hyperthermia and dehydration the risk of making mistakes in both cognitively dominated tasks is doubled and simple motor performance impaired. Direct exposure of the head to solar radiation (simulated sun equal to typical outdoor summer levels) profoundly reduces motor-cognitive performance, indicating that previous observations from laboratory experiments may have markedly underestimated the effects of heat stress on cognitive function. Heat acclimation may improve thermal resilience, but it cannot protect complex motor performance during exposure to uncompensable heat stress.

Conclusions: The present observations let us conclude that hyperthermia, dehydration and solar-radiation profoundly reduce motor-cognitive performance. Additionally, heat acclimation was unable to protect against the decline in motor-cognitive performance caused by hyperthermia. Collectively, these studies illustrate the detrimental effects of hyperthermia and associated conditions on motor-cognitive performance.

Passive Heat Stress Effects on Time Perception and Timed Decision Tasks

ABSTRACT. Introduction: Research in the field of time perception suggests that core body temperature mediates the subjective experience of time, and research in the field of decision making indicates the importance of a correct estimation of the passing of time for making decisions. Here we hypothesized that compared to a normothermic state, a hyperthermic state speeds-up time perception, which leads to a decreased accuracy (ACC) and response times (RT) of a timed decision task. Furthermore it is hypothesized that the perception of time and accuracy of a timed decision task correlates with thermophysiological variables body core temperature (Tc) and heart rate (HR), and subjective task load, rate of perceived exertion (RPE), thermal sensation (TS) and thermal comfort (TCOMF).

Method: Young adult males (N=29) participated in two 60min head-out water immersion conditions (36.5°C NEUTRAL and 38°C WARM). Participants performed an interval timing task and an two-alternative forced choice task at t=-15, t=20 and t=60. Physiological measurements included core temperature (bodycap) and heart rate (polar).

Results: Tc and HR were significantly higher in WARM vs. NEUTRAL condition at t=60 (Tc: 38.4±0.2°C vs. 37.2±0.1°C, p<0.01; HR: 106±9BPM vs.88±7BPM, p<0.01, mean±SD). Change in estimation of passing of time (T=60vs.T=-15) was significantly larger in WARM vs. NEUTRAL condition (-0.11±0.18vs.0.07±0.32,p<0.01). Response times decreased both in WARM condition (-0.07±0.06,p<0.01) and NEUTRAL (-0.03±0.06,p<0.03), however the decrease was larger in WARM vs. NEUTRAL (p<0.02). The accuracy decreased in WARM (-0.03+/-0.05,p<0.01) and NEUTRAL condition (-0.02 +/- 0.04,p<0.05), however no significant difference in accuracy was detected in WARM vs. NEUTRAL (p>0.12). ΔTc and ΔTS were significantly related to ΔRT (r2=0.42,p<0.01; r2=0.1,p<0.04 respectively), ΔTCOMF and ΔRPE were significantly related to ΔACC (r2=0.12,p<0.03;r2=0.12,p<0.03, respectively).

Conclusions: Passively induced hyperthermia (Tc=38.5°C) significantly affects time perception and response time but not accuracy of a decision task. Accuracy revealed a small correlation with subjective indicators TCOMF and RPE.

Using WBGT Heat Risk from Weather Forecasts for Cancelling Sport Events: Focus on False Positives and False Negatives

ABSTRACT. Introduction: Exertional heat stress can result in performance loss and health risks for athletes. One frequently used environmental heat stress index is the wet bulb globe temperature (WBGT). The WBGT is defined for outdoor conditions as the weighted average of dry bulb, wet bulb and black globe temperature. These variables can be calculated from weather forecast data. Therefore, heat related risk for athletes can be predicted, and used as a policy recommendation whether an event should be rescheduled or cancelled. However, given that rescheduling or cancellation can be costly, knowledge on the probability of false positives and false negatives is warranted.

Method: Air temperature, globe temperature, air velocity and relative humidity were measured during a 14-day outdoor summer sporting event in Melbourne, Australia. From these values the WBGT was calculated according to the Australian Bureau Of Meteorology. For the same period weather forecasts (1-2h forecasts; were collected at a position <3km from the event location at 11:00, 14:00 and 17:00. WBGT was calculated from forecasted data using the Liljegren method. WBGT cancellation levels were assumed to be the ACSM position statement (2007), WBGTextreme>32.3°C. WBGT calculated from measured data was considered the reference.

Results: WBGT False positive rate was 17% (6 false positive over 35 time points), and 0% false negative rate. The median and range of difference between estimated WBGT from measured data and WBGT from forecasted data was +2.5°C [-2.8°C to +6.7°C]. Overestimation of globe temperature is the largest factor +10.0°C[+1.2°C to +20.7°C], which may be caused by assuming zero cloud cover and an underestimated effect of wind.

Conclusions: Cancelling or rescheduling a sport event based on forecasted WBGT data has a relatively high false positive rate and no false negatives. Therefore the described forecast method is likely overprotective potentially to the extent that policy recommendations might be ignored.

Contribution of wetted clothing to body energy exchange and heat stress

ABSTRACT. Modelling the energy exchange between the body and the environment in extreme conditions can prove challenging as the certain assumptions built into the traditional models break down. Elson [1, 2] demonstrated that a two-node model can be used to predict performance, but two important constraints must be considered for the modelled population. First, the sweat rate models presented in literature should be tuned to the population of interest. Second, the effect of excess sweat must be included in any prediction if heat stress is of interest. The models developed by Elson are extended to more closely explain the heat transfer between the wet clothing and human body

1. Elson, J. and S. Eckels, Contribution of wetted clothing to body energy exchange and heat stress. Journal of Thermal Biology, 2018. 78: p. 343-351. 2. Elson, J. and S. Eckels, An objective method for screening and selecting personal cooling systems based on cooling properties. Applied Ergonomics, 2015. 48: p. 33-41.

14:30-15:00 Session 16: Posters Thursday
Location: Marble hall
Comparison of different clothing area factor (fcl) calculations based on picture analysis in Adobe Photoshop

ABSTRACT. Introduction: The clothing area factor (fcl) is an indicator of the increase in surface area relative to the nude body for calculation of heat loss from the clothed body to the environment. The aim was to compare differences from two equations for the fcl calculation by the photographic method using Adobe Photoshop.

Method: Thirty-five modern western indoor clothing sets (19 male and 16 female) were tested on a thermal manikin Tore. In order to calculate fcl for the clothing sets, front and side views of nude and dressed manikin were photographed against bright background without flash for creating a dark silhouette. The pictures were taken in three different sessions. Each session included nude manikin pictures as the camera position or zoom level might have differed session wise. Colour information was discarded by selecting Grey scale mode. Then curve (Image/Curve option) was adjusted to increase the manikin contrast against the background. The surrounding objects were eliminated by selecting black manikin silhouette, inversing the selection and deleting background. Thereafter, background residues and all protruding elements, e.g. connection cables were deleted. The surface areas were estimated based on counted pixels and percentiles of black areas. Brightness and Contrast were adjusted to minimum and maximum levels, respectively, in the Histogram before recording the percentiles and pixels. Then the black silhouette was selected with Magic wand tool and pixel number was recorded followed by deselecting all and reading percentile of pixels when cursor was left at level 100 in the Histogram. The fcl-s for comparison were calculated based on both pixels and percentiles by two equations: f_cl=(〖Front〗_clothed+〖Side〗_clothed)/(〖Front〗_nude+〖Side〗_nude ) f_cl=(〖Front〗_clothed/〖Front〗_nude +〖Side〗_clothed/〖Side〗_nude )/2

Results: The fcl means (SDs) for Eq. 1 and Eq. 2 were similar for both pixels and percentiles: 1.17 (0.07) and 1.18 (0.07), respectively. The fcl means (SDs) differences equation wise for pixels and percentiles were 1.04 (0.55) % and 1.00 (0.51) %, respectively. The calculated basic means (SDs) insulation (Icl) did not differ when using the respective pixels and percentile fcl values.

Conclusions: The results suggest that two equations provide fcl values with a small difference based on either pixels or percentile of picture. The two equations did not affect the calculated intrinsic clothing insulation, Icl.

Air conditioning needs of workers in long-haul trucks can be substantially reduced with high-reflectivity paints, enabling important fuel savings in the European transportation sector
PRESENTER: Tiago S. Mayor

ABSTRACT. Introduction: Transportation workers are often exposed to thermally challenging conditions while driving for long periods under high temperature and solar radiation. This is taxing for the workers, so air-conditioning (AC) is used to counter the external thermal loads and maintain comfortable temperatures inside the cabins. Yet, this increases fuel consumption and tailpipe emissions with clear detrimental environmental effects, thus it is crucial to consider alternative strategies to protect the workers while minimizing the AC loads needed. Method: We have numerically investigated the thermal loads affecting the cabin of long-haul trucks, considering the environmental conditions prevailing across the different regions of Europe throughout the year. We studied the AC loads and related fuel consumption to maintain comfortable cabin temperatures during entire workdays. We analysed the potential reductions in AC loads and fuel consumption that can be obtained by using high-reflectivity paints on the cabin external surfaces. Results: Southern Europe accounted for 38% of the European fuel costs related to AC cooling, despite representing only 26% of the trucks fleet. The yearly AC fuel costs of the southern European trucks are almost 12 times higher than those in the north, and 12-49% higher than those in the eastern/western regions. The use of high-reflectivity paints by the entire European long-haul fleet can substantially reduce the cooling AC loads. Paints reflecting 70% of the solar radiation instead of 32% (average value) can reduce the European transportation AC fuel costs by up to 39% or 1301 million euros per year, i.e. 0.6% of the yearly total fuel cost. Conclusions: The optical properties of paints used in truck cabins have strong impact on the AC loads needed to maintain comfortable cabin temperatures. Important reductions in fuel consumption are possible by carefully choosing the paint properties, indicating potential for substantial savings by the European transportation sector.

Development of a protocol to assess thermoregulatory impacts of multiple garments in a single, 90 minute trial
PRESENTER: Grant Simmons

ABSTRACT. Introduction: We sought to accelerate apparel thermoregulatory research studies (on humans) by developing a protocol to evaluate the impacts of multiple apparel conditions within a single experimental session.

Method: We selected a combination of exercise intensity and environmental conditions that could be sustained for 90 minutes by most participants and incorporated a 30 minute ‘preload’ in which steady state responses could be achieved, followed by four 15 min apparel conditions to be compared within the exercise trial. Accumulation of moisture (from sweat) in the apparel microclimate between shirt and skin was selected as the dependent variable and measured by assessment of microclimate water vapor pressure (MCvp). Study 1 was designed to assess variability in MCvp responses across four apparel conditions in which versions of the same shirt were worn. Study 2 was designed to assess variability in MCvp responses across four apparel conditions in which different garments were worn which varied widely in vapor permeability. A total of 12 subjects (6 males, 6 females) walked on a treadmill at a speed of 3.5 mph, 8% incline for 90 minutes in controlled environmental conditions of 20°C and 40% relative humidity. MCvp was measured at six locations over the torso using ibuttons taped to the skin, facing outward into the apparel microclimate (ANOVA between apparel conditions).

Results: MCvp was not different (p=0.11) across the four conditions in which subjects added/removed versions of the same shirt in study 1, nor were there differences between the increase in MCvp during each 15 minute condition (p=0.20). MCvp was higher in ‘heavier’ garment conditions than in ‘light’ garment conditions in study 2 (p<0.001), and was not different between duplicate conditions in the same garment (light or heavy; p>0.40 both comparisons).

Conclusions: We conclude this protocol is valid for thermoregulatory evaluation of multiple apparel conditions within a single, 90 minute experiment.

Required clothing insulation (IREQ - ISO 11079) and difference of thermal sensations between genders
PRESENTER: Jakob Petersson

ABSTRACT. Introduction: The aim was to study if there are profound gender differences in thermal sensation during student laboratory exercise in an extreme cold environment. ISO 11079 (IREQ) was used to predict insulation.

Method: Ninety young healthy students with similar BMI, 45 males (24.7 ± 4.0 years; 180.2 ± 8.9 cm; 73.5 ± 7.8 kg) and 45 females (24.0 ± 3.0 years; 169.7 ± 6.3 cm; 63.6 ± 7.9 kg) were exposed to extreme cold in a climatic chamber at the temperature -35 ˚C and 0.4 m/s air velocity for 45 minutes. Average estimated metabolic rate for the exposure was 94 W/m2 based on ISO 8996. The thermal sensation was recorded every 10 minutes on a scale -4 (very cold) to +4 (very warm) for feet, hands, whole body and face. Clothing insulation was estimated by ISO 9920. The students were asked to bring their own clothing.

Results: IREQ for 45 minutes’ exposure was 3.2 clo for comfort (IREQneutral) and 2.9 clo for slight cooling (IREQminimal). The average available clothing insulation worn was 2.1 ± 0.4 clo for males and 2.3 ± 0.4 clo for females. Males experienced -1.5 ± 1.4 for feet, -1.0 ± 1.3 for hands, 0.2 ± 1.1 for whole body and -0.2 ± 1,3 for face. Females experienced -2.4 ± 1.5 for feet, -1.7 ± 1.5 for hands, -0.8 ± 1.4 for whole body and -0.8 ± 1.4 for face.

Conclusions: Female subjects recorded lower thermal sensations than male subjects, this may be partly explained by body differences between the genders. The females also report greater cold sensation in extremities than males which may be influenced by stronger general body cooling. The exposure time was relatively short making influence by initial thermal inertia somewhat high. Students tend to underestimate clothing need for low activity in extreme cold.

Stress levels in simulation-based training of laparoscopic surgical skills: A pilot study

ABSTRACT. Introduction: Stress in excess has negative effect on surgeon's performance during procedures in the clinic. Simulator training enables technical surgical training outside the operating room and allows surgeons to improve their technical skills in a low stressor environment, where they can perform targeted and repetitive exercises without fear of serious consequences. A question of interest relating to simulation-based training is whether the lack of real-life consequences and associated lack of stressors and low stress levels might affect the ability to transfer these technical skills to clinical settings. Little is known about stress levels of surgeons in training using simulation-based training and the transfer of skills. The objective of this study was to compare stress levels when using analogue and virtual reality simulators versus suture exercises on animal organs.

Method: In this study, four test subjects who all were surgeons in training, underwent an experimental study, in which we applied both objective measurements: heart rate variability (HRV) and heart rate (HR), and subjective evaluations: Spielberger State-Trait Anxiety Inventory (STAI) to assess their stress levels. The data was obtained at rest and during the simulation exercises and the suture exercises.

Results: We found during rest that mean HRV was 2.4±2.3 (LF/HF), mean HR was 72.0±2.8 (beats/min) and mean STAI was 8.5±3.1 (score). During analogue simulation mean HRV was 8.5±6.4 (LF/HF), and mean HR was 84.4±8.7 (beats/min) and mean STAI was 11.9±2.2 (score), and during VR simulations mean HRV was 7.8±4.2 (LF/HF), mean HR was 83.6±8.7 (beats/min) and mean STAI was 11.8±2.8 (score). During suture mean HRV was 6.9±3.4 (LF/HF), and mean HR was 85.3±6.4 (beats/min) and mean STAI was 11.0 ± 0.0 (score).

Summary: The HRV measurements suggest higher stress levels when doing exercises on the analogue and VR data simulators compared to animal tissue suture exercises. The results from the subjective measurements suggest the same tendencies. This may be explained by the application of unfamiliar techniques and skill set when training on analogue and VR data simulators.

Effectiveness of ventilated vest at various ambient relative humidities

ABSTRACT. Introduction: Climate change presents one of the biggest global health threats of the 21st century. One of the direct consequences of global warming are more frequent and intense summer heat waves, which create greater heat stress in industrial settings. The maintenance of workers’ health and well-being relies on strategies to mitigate such heat stress. The present study investigated the benefit of cooling vests in augmenting evaporative heat loss in a range of ambient relative humidities. Methods: The study evaluated the evaporative capacity of a commercially available ventilated vest, using a thermal manikin. The vest, combined with body armour (BA) was tested at 35°C (equal to manikin temperature) at different ambient relative humidities (RH; from 10 to 90%), compared with just a T-shirt in combination with BA. The vest was also tested on three male participants, while walking on a treadmill at 20°C. During this trial we measured heat flux. Results: At 50% RH the vest increased the evaporation to 5 g.min-1, compared to T-shirt with 2 g.min-1. At 10% RH the difference was doubled (with vest: 8 g.min-1, without: 4 g.min-1). The vest effectiveness was improved when fitting tightly on participant (ectomorph:56±29, mesomorph:67±23, endomorph:70±16 W.m-2). Conclusions: The cooling vest augmented evaporation from the manikin at ambient RHs ranging from 10 to 70%. A properly designed vest can contribute to the mitigation of heat stress in outdoor and indoor settings.

Acknowledgements: The study was supported, in part, by the Slovene Research Agency (project no. Z7-9412), the Swedish Armed Forces (grant no: 9220907) and H2020 project Heat Shield (contract no. 668786).

The upper limits of allowed heat exposure for summer work uniform and vapor impermeable protective clothing estimated using PHS and TNM
PRESENTER: Tomonori Sakoi

ABSTRACT. Introduction: The predicted Heat Strain model (PHS) and the Two Node Model (TNM) are widely used for predicting human responses to hot environments. Sweating in PHS is defined by the steady heat balance of the model. Sweating of TNM is based on body temperature deviation from its set point. In this study, we compared the core temperatures of these two models for workers wearing Summer Work Uniform (SWU) and Vapour Impermeable Protective Clothing (VIPC) focusing on the upper limits of the allowed heat exposure. Method: We calculated core temperature changes of these models for gradually increasing environmental temperature at three relative humidity levels (20%, 50%, and 70%). We drew the core temperature curves against the environmental temperature for each clothing and relative humidity condition. Then, we estimated the inflection points of the environmental temperature at which the slope of the curves changed significantly. The determined inflection points were compared with the upper limits of the prescriptive zone for these conditions reported by Bernard et al. (2005). Results: Inflection points for PHS appeared more clearly than for TNM. The Inflection points of PHS coincided well with the reported values for SWU while for VIPC the obtained values were higher than the reported ones for the lower relative humidity. Because of the more gradual changes of the core temperature slope for TNM, we could not determine the inflection points of TNM clearly. However the inflection points of TNM seem to be close to the reported values for both types of clothing. Conclusions: The inflection points appear clearly for PHS. They coincided well with the reported values for SWU. While the inflection points of TNM were not determined clearly, they seemed to be close to the reported values for both types of clothing.

Evaluation of Physiological Impact of Protective Clothing Fabrics for Firefighters by ISO 18640 Method

ABSTRACT. Introduction: Continuation of an earlier study, the heat protection and the thermal and evaporative properties of 7 personal protection clothing (PPC) materials for the prediction of thermal physiological comfort (ISO 18640-1) have been evaluated. In this study, it was intended to focus on the investigation of physiological heat burden and work safety on firefighters. By coupling the Sweating Torso to a mathematical model for thermo-physiological responses, the thermo-physiological impact of protective clothing was estimated and the maximum allowable work duration (MAWD) for defined environmental conditions and a defined activity protocol were predicted by Thermal Human Simulator (THS) measurements (ISO 18640-2).

Method: The standard scenario for THS is defined as an ambient condition of 40 °C, 30 % RH, wind speed of 1 m/s, and physical activity of 6 MET. The initial condition of the human body is assumed to be thermo-neutral (Tco = 36.8 °C; Tm,sk = 34.2 °C) and the onset of heat stress is defined as the core body temperature of 38.5 °C. The wicking layer was added next to the Torso skin and both MAWD with and without a frame (simulating the air gap) between 7 PPC fabric assemblies were investigated.

Results: THS predicted the Tco and Tm,sk, and sweating water of the system, and MAWD was manually detected at the Tco of 38.5 °C. It was found that the highest total sweat water was 856.9g for PPC2 and the lowest of 797.9g for PPC1 among the 7 fabric assemblies. The MAWD results showed that the range was from 31 to 34 min with a frame, and was 60.0 to 71.7 min without a frame. The statistically significant correlations are between MAWD and Ret of ISO 11092 (p=.038), MAWD and IC, initial cooling, of ISO 18640-1 (p=.044), and MAWD and evaporated water of ISO 18640-2 (p=.000), respectively.

Conclusions: In the previous study, all 7 PPCs meet the requirements of heat protection and Ret of EN 469:2005. In the case of ISO 18640-1 test standard, PPC6 revealed the best initial cooling efficiency, and PPC7 had the lowest Tm,sk during the later period of the exercise phase. On the other hand, PPC1 showed the highest Tm,sk during exercise, suggesting that lots of accumulated heat occurred. By ISO 18640-2 method, the MAWD with frame presented almost twice compared with that of no frame applied, indicating that the air gap was an important factor on it. With all of the indices related to comfort, Ret seemed to be more critical than Rct and imt. It was found that ISO 18640-1 can give us some useful information in the detection of cooler PPC, while ISO 18640-2 method can recommend a work safety index, despite the fact that it may need a more detailed discussion of proceeding of the measurements including the setting of scenarios and comparison of different labs. These methods are all valuable for material tests. Both of ISO 18640-1 & -2 were studied by wear trials for validation, however, the future work should include either sweating thermal manikins or human subject evaluations.

Observations of regional differences in finger skin blood flow fluctuations
PRESENTER: Norikazu Ohnishi

ABSTRACT. Introduction: Blood vessels of the finger skin play a vital role in regulating body temperature in humans. The rate of heat dissipation from hands depends on the blood flow of arterio-venous anastomoses (AVAs) which are able to change their diameter dramatically by dilating and constricting. Laser Doppler flowmetry (LDF) is widely used to observe skin blood flows (SBFs) including changes of blood flows in AVAs of fingers and toes as a representative value of the whole skin site, although its measurement area is quite small. This study aims to compare fluctuations of SBFs in some finger skin sites in order to confirm the synchronicity of SBFs measured by LDF in the different finger skin sites and explore the possibility of affecting the rate of heat dissipation, if asynchronous changes are observed. Method: We examined healthy young females (N = 25) wearing only a T-shirt and short pants in a climatic chamber set at 32 degree C. In each trial, after reaching thermal equilibrium, SBFs were measured by using LDF on the ventral and dorsal distal phalanx and the dorsal middle phalanx of the right index finger. Waveforms of SBFs were compared between the intra- and inter-skin sites of the finger to confirm synchronicity of fluctuations. Results: In all sites of all participants, finger SBFs were around maximal levels with occasional spontaneous drops. While the SBF behaved synchronously between the three sites in almost all cases, SBFs measured in the ventral distal phalanx and the dorsal middle phalanx behaved asynchronously in some cases. Conclusions: Observed asynchronous SBF fluctuations between different finger sites could be related with the location of probes and uneven blood distributions to vascular networks caused by different responses of AVAs to sympathetic activity. The impact of those discrepancies on the heat dissipation rate could be limited.

Effects of nitric oxide synthase with Ca2+-activated and ATP-sensitive K+ channels on local forearm sweat rate in older men during exercise in the heat

ABSTRACT. Introduction: Nitric oxide synthase (NOS) inhibition attenuates sweating in young men. However, NOS-dependent sweating is diminished in older men. Calcium-activated and ATP-sensitive potassium (KCa and KATP) channels also modulate sweating in young men exercising in the heat, although their role in older men remains uncertain. Additionally, the potential crosstalk between NOS and KCa and KATP channels on sweating in older men has not been previously evaluated under these conditions. Therefore, we examined the separate and combined effects of NOS with KCa and KATP channels on local sweat rate (LSR) in older men exercising in the heat. Method: In thirteen habitually active older men (61±4 years), LSR (assessed via ventilated capsule) was measured at six dorsal forearm skin sites receiving either: 1) lactated Ringer’s (Control), 2) 10 mM NG-nitro-L-arginine methyl ester (L-NAME, NOS inhibitor), 3) 50 mM Tetraethylammonium (TEA, KCa channel blocker), 4) 5 mM Glybenclamide (GLY, KATP channel blocker), 5) GLY+L-NAME, or 6) TEA+L-NAME, via intradermal microdialysis. Participants rested in the heat (35°C) for 70 min, followed by 50 min of moderate intensity exercise (~55% VO2peak) and 30 min of recovery. Results: During rest, LSR was not different between treatment sites (all P>0.05). End-exercise LSR at Control (1.81±0.61 mg·min−1·cm−2) was not different from GLY (1.76±0.81 mg·min−1·cm−2), TEA (1.71±0.65 mg·min−1·cm−2), L-NAME (1.65±0.57 mg·min−1·cm−2) or GLY+L-NAME (1.78±0.56 mg·min−1·cm−2) (all P>0.05). However, combined TEA+L-NAME (1.49±0.56 mg·min−1·cm−2) was attenuated relative to Control (P<0.05). Conclusions: While the independent effects of NOS inhibition or KCa or KATP channel blockade had no effects, a combination of NOS inhibition and KCa channel blockade attenuated sweating in older men exercising in the heat. The interactive effects of these mechanisms on regulating heat loss in older men at the level of the eccrine sweat gland requires further investigation. Funding: Natural Science and Engineering Research Council of Canada (G. P. Kenny).

Effect of cold intensity on cold-inducible RNA-binding protein release

ABSTRACT. Introduction: Cold-inducible RNA-binding protein (CIRP) is an environmentally induced protein that upregulates during cold exposure. During moderate cold exposure (such as during cold-water immersion), decreased core temperature can lead to cellular injury and CIRP may assist with recovery. No previous studies have examined CIRP after cold exposure in humans in vivo and thus, the purpose of this study was to examine changes in plasma CIRP concentration in males after mild (no core temperature change) and moderate cold exposure.

Method: Six healthy, morphologically similar males (25.5±3.5y) participated in mild cold exposure and five males (25.6±3.6y) participated in moderate cold exposure. Participants completed a 30min habituation period followed by 60min of mild cold exposure wearing a liquid conditioned suit (LCS; 5°C) or 90min of moderate cold exposure using cold-water immersion (CWI; 20°C). Skin temperature was measured on 12-sites during the LCS and core temperature was measured using a telemetric pill. Plasma was collected pre-, post-, 4h post-, and 24h post-cold exposure. CIRP was analyzed via ELISA.

Results: Mean skin temperature at the end of mild cold exposure was 24.3±1.1°C (no change in core temperature) and core temperature at the end of moderate cold exposure was 36.2±0.9°C. During the mild cold exposure, there were no significant differences (p>0.05) in CIRP protein expression at any time point. In contrast, during the moderate cold exposure, 4h plasma CIRP was significantly higher (p=0.019) than post-exposure with no other significant differences (p>0.05) between any other time point.

Conclusions: CIRP was significantly upregulated only after cold exposure that elicited a decrease in core temperature (4hr post-CWI). The upregulation of CIRP seen in conjunction with an increase of cold intensity may indicate that CIRP can act as a cold stress marker at higher levels of cold stress even in the absence of hypothermia.

Evaluation of radiative performance of equestrian helmets

ABSTRACT. Introduction: Equestrianism is a popular activity that extends from amateur participation to international success. Studies show that 3.5 million people have ridden a horse in 2010 -11 (National Equestrian Survey) in Britain. There has been growing concern about the increase in horse riding related accidents. Among the injured equestrians admitted in hospitals, 60% are caused by head injuries which could be prevented by helmet usage. The aim of this study was to evaluate radiative heat loss characteristics of three equestrian helmets with the use of a thermal manikin head and to improve thermal performance using design guidelines to optimize bicycle helmets for cooling performance.

Two commercial equestrian helmets and a equestrian helmet modified based upon design guidelines were tested using a thermal manikin head with 9 measurement zones and an external radiative heat source (150W infrared heat bulb placed at an angle of 60° with head) to simulate intermediate radiation condition. Surface temperature of manikin was 30°C and ambient temperature was 20°C. Power required to maintain the prescribed surface temperature was recorded as heat loss. The helmets were evaluated at 6m/s, an average prescribed by FEI. The cooling performance of bicycle helmets was modified using large inlets and larger outlets connected via internal channels to induce a low-pressure zone at the rear of the helmet

The overall radiative heat gain of nude head was observed to be 9 W. The helmets as predicted shield the external radiation source from the head. The radiative heat gain observed with commercial helmet without vents was observed to be 0.72 W and the radiative heat gain with commercial helmet with vents was observed to be 0.93 W. The custom helmet showed a radiative gain of 2 W which is significantly comparable to the commercial helmets. This research shows that the cooling performance of equestrian helmets can be significantly improved.

Testing of Sleeping Bags per EN ISO 23537-1 with Different Chamber Air Temperatures

ABSTRACT. ISO 23537-1:2016 provides a method to determine total thermal resistance and temperature rating predictions for sleeping bags using a thermal manikin. The total thermal resistance includes resistance of the sleeping bag system and the outer air layer. This outer air layer is a combination of convective heat transfer and radiation exchange. It is established that the radiation heat transfer decreases with chamber air temperature and bag insulation. Natural convection on the other hand is driven by temperature difference and increases with decreased environmental temperature. It is not known if the combined radiation and convective heat transfer in the air layer increases or decreases as environmental temperature changes. Furthermore, the ISO 23537 standard limits the air temperature of the test chamber to 10 ± 5 C, but bags designed for environments to -20 C may be tested. The current study documents the change in bag insulation values for different bag types as chamber air temperature changes.

A Free Software to Predict Heat Strain According to the ISO 7933:2018

ABSTRACT. Introduction: Over the last century several thermal stress indices have been developed to estimate the thermal strain experienced by workers in occupational settings. Among them, it is worth mentioning the predicted heat strain (PHS) model which was specifically developed to predict the heat strain in occupational settings. However, it has been mentioned that its calculation is so sophisticated that is not used in industry. Therefore, our primary objective in this study was to design and implement the FAME Lab PHS Calculator software (PHSFL) ( to simplify the calculation of the PHS model. Our secondary objective was to assess: (i) the criterion-related validity of the PHSFL by comparing its results against those obtained using the original ISO 7933:2018 code; and (ii) the construct validity of the PHSFL by comparing its results against those obtained via field experiments performed in human participants during work in the heat. Methods: Five grape-picking workers worked for eight consecutive hours in environmental temperature (28.5±3.3°C) ranging from 18.6°C to 35.1°C. Core temperature (Tc) and skin temperature (Tsk) data were collected throughout the work-shift. Thereafter, the measured data were compared with data predicted using PHSFL. Funding was provided by European Union’s Horizon 2020 Marie Curie “ICI-THROUGH” project under the Grant agreement no. 645710. Results: Criterion validity demonstrates that PHSFL provides valid results within the required computational accuracy, according to Annex F of ISO 7933:2018. The construct validity showed that the measured Tc (37.6±0.2°C) and Tsk (34.9±1.5°C) were strongly related with the predicted Tc (37.6±0.1°C) and Tsk (35.5±0.8°C) values (Tc:r=0.573; Tsk:r=0.850; all p<0.001). Furthermore, root mean square errors (RMSE) and 95% limits of agreement (LOA) were minimal between measured and predicted Tc (RMSE: 0.3°C; LOA: 0.06±0.58°C) and small between measured and predicted Tsk (RMSE: 1.1°C; LOA: 0.59±1.83°C). Conclusion: The PHSFL software demonstrated strong criterion-related and construct-related validity.

Effects of pre-exercise voluntary hypocapnic hyperventilation on cardiovascular responses to simultaneous initiation of exercise and apnea
PRESENTER: Mizuki Sakamoto

ABSTRACT. Introduction: Apnea during exercise decreases arterial O2 pressure, whereas it substantially modulates cardiovascular responses including heart rate, arterial blood pressure, and cerebral blood flow responses. However, relatively unknown is that cardiovascular responses to simultaneous initiation of exercise and apnea, a situation that occurs when diving in the water. Also, to extend apnea duration, divers occasionally perform voluntary hyperventilation prior to exercise, which washes out CO2 from the blood, leading to reductions in arterial CO2 pressure (hypocapnia). Whether voluntary hypocapnic hyperventilation modulates cardiovascular responses to simultaneous initiation of exercise and apnea remains to be investigated. Method: Fourteen young adults (7 men and 7 women) commenced a moderate-intensity cycling and maximal apnea at the same timing that was preceded by 1) 3-min spontaneous breathing or 2) 3-min voluntary hyperventilation resulting in a reduction in end-tidal CO2 pressure to 22±6 (SD) mmHg. 1) and 2) were also performed without apnea. Results: Apnea duration was extended by voluntary hyperventilation relative to spontaneous breathing trial (62±7 vs 43±9 s). Arterial oxygen saturation estimated by pulse oximetry during apnea exercise was elevated by voluntary hyperventilation, whereas that measured at end-apnea was reduced by voluntary hyperventilation (87±10 vs 69±14% vs; p < 0.01, d = 1.46). Mean arterial pressure (84±26 vs. 98±17 mmHg, P = 0.002, d = 0.61) and middle cerebral artery mean blood flow velocity (56±18 vs 70±15 cm sec-1, P = 0.001, d = 0.84) during apnea exercise in the hyperventilation trial were lower than the spontaneous breathing trial, albeit these cardiovascular variables at end-apnea were not different between the trials. Conclusions: Our results suggest that when exercise and apnea are simultaneously initiated, pre-exercise voluntary hypocapnic hyperventilation blunts cardiovascular responses, but this effect is diminished at end-apnea.

Upper body skin temperature during exercise in a warm environment: a sex comparison

ABSTRACT. Introduction: Skin temperature is greatly affected by exercise. However, majority of researches that investigated skin temperature focused on males, which might not be applicable for females. This study aimed to investigate differences between female local skin temperature and male. Method: Seven young females with B-cup breasts and three young males volunteered to participate in the experiment in a warm environment (30°C, 44%RH). Male subjects wore a T-shirt and shorts while female subjects wore an additional layer of a sports bra. The exercise protocol consisted of 5 min walking for warming up, three alternations between 10 min jogging and 5 min walking, followed by 10 min sitting rest to recover. Skin temperature was measured at breast/chest, abdomen, back and waist. Results: Female breast and abdomen temperatures showed a stepped decrease along with the alternation between jogging and walking, while the temperature at back and waist increased. The four regional skin temperatures all showed an upward trend in males. It is speculated that the prominence of female breasts results in almost no air gap at breast and a bigger air gap at abdomen under the T-shirt. The decrease of skin temperature at breast might be due to the increased heat conductivity of the wet sports bra while the decrease of skin temperature at abdomen might be caused by the increased ventilation resulting from the pump effect during exercise. Conclusions: Opposite change of local skin temperature was observed on the anterior between sexes during exercise. Such difference needs to be considered in sportswear design for females.

Effects of moisture content on the dual thermal protective/ thermal hazardous performance of multilayer protective clothing under hot steam exposure

ABSTRACT. Introduction: Thermal protective clothing (TPC) actually may have a dual impact because it not only resists heat transfer from environmental thermal threats, but also may impose thermal hazards on human skin due to the discharge of stored energy. The dual thermal-protective/ thermal-hazardous performance of TPC are rather complicated when it gets wet from internal and external sources (i.e. profuse perspiration and atmospheric water), and especially when it is exposed to a pressurized hot steam condition. Method: A steam and hot fluid tester was employed to generate the saturated and superheated steam at a temperature of 133.7 C and a pressure of 200 kPa. The outer shell and thermal liner of a multilayer fabric system were chosen to be pre-wetted before the test, and each fabric layer had four moisture levels. Several indices were used to quantitatively assess the dual thermal-protective/thermal-hazardous performance of TPC. Empirical models were successfully established to predict the relationship between the moisture and the performance of TPC. Results: The results showed that the increasing of external moisture enhanced thermal protective performance as it decreased heat absorption of the skin and increased skin burn injury time under direct steam exposure, but it did not have significant effect on the thermal hazardous performance through heat discharge. The increasing of internal moisture generally had a positive effect in reducing heat transfer during exposure, but during cooling it did the opposite, increasing heat discharge to the sensor. It demonstrated that thermal protective performance was more influenced by the external moisture; the thermal hazardous effect during cooling, however, was more affected by the internal moisture. Conclusions: The results showed that moisture distribution was a key parameter to consider in the reliability of TPC since the moisture content and location have a complex influence on the dual thermal-protective/ thermal-hazardous performance.

The Effects of Acute Dopamine Re-Uptake Inhibition on Executive Function and Working Memory during Passive Hyperthermia

ABSTRACT. Introduction: Passive hyperthermia ≥1.0˚C in core temperature (Tc) impairs executive function and working memory, potentially from hyperthermia-induced alterations in dopamine concentrations. The dopamine-reuptake inhibitor methylphenidate (MPD) increased time trial power output and final Tc while reducing perceived exertion in the heat, such that increased dopamine activity may alter mental function.

Method: 10 male participants completed a randomized, double-blinded study consisting of two experimental sessions where participants received either 20 mg MPD or placebo (PLA). Following 60 min wash-in, cognitive function was tested at baseline (37.1±0.6˚C) and after passive heating to 38.6±0.4˚C. Executive function was tested using the Groton Maze Learning Task (GMLT) and working memory by a Two-Back Test (TBT) (CogState, CT). Right middle cerebral artery velocity (MCAv) was measured continuously using transcranial Doppler at 400 Hz. Thermal perception was measured using the Thermal Comfort (TC, 1-4) and Thermal Sensation (TS, 1-7) scales (presented as quartile (q1-q3)).

Results: TBT errors significantly (p=0.006) increased with hyperthermia, but no significant differences between MPD or PLA at either baseline (MPD:1.0±1.4, PLA:1.0±0.8 errors) or hyperthermia (MPD:2.0±2.0, PLA:4.0±2.6 errors). GMLT errors (p=0.011) increased with no difference in speed (p=0.147) with hyperthermia, with no significant differences between MPD or PLA at either baseline (MPD:28.0±8.3, PLA:25.0±7.5 errors; MPD:125.3±19.5, PLA:124.2±21.1 s) or hyperthermia (MPD:33.0±6.7, PLA:31.0±8.4 errors; MPD:123.2±25.5, PLA:114.6±28.8 s). MCAv decreased with passive hyperthermia (p=0.009), with no significant differences between MPD or PLA at either baseline (MPD:56.0±11.2, PLA:61.0±11.8 cm·s-1) or hyperthermia (MPD:45.0±8.5, PLA:46.0±7.5 cm·s-1). TC (p<0.001) and TS (p<0.001) increased with hyperthermia with no difference between MPD or PLA at either baseline (TC: MPD: 1.0(1-1), PLA:1.0(1-1); TS: MPD:4.0(3-4), PLA: 4.0(3-4)) or hyperthermia (TC: MPD: 4.0(3-4), PLA: 4.0(3-4); TS: MPD: 7.0(7-7), PLA: 7.0(7-7)).

Conclusions: An acute 20 mg dose of a dopamine re-uptake inhibitor was unable to counteract the hyperthermia-induced (+1.5˚C Tc) decrements in working memory or executive function.

The Effects of Cerebral Blood Flow on Working Memory and Executive Function during Passive Hyperthermia

ABSTRACT. Introduction: Passive hyperthermia (≥1.0˚C in core temperature) impairs working memory and executive function, potentially from hyperthermia-induced hypocapnia that elicits a decrease in cerebral blood flow.

Method: Nine males completed a randomized, single-blinded study consisting of isocapnia (ISO, end-tidal CO2 clamped at eucapnic baseline) or poikilocapnia (PKC, no end-tidal CO2 control) during passive heating using a water-perfused suit (water temperature ~49°C). ISO was maintained using a breath by breath end-tidal forcing system, and right middle cerebral artery velocity (MCAv) was measured continuously using transcranial Doppler at 400 Hz as an index of cerebral blood flow. Mental function was tested at baseline (36.5±1.3˚C) and at 38.5±0.4˚C. Working memory was tested with a Two-Back Test (TBT) while executive function was tested using the Set Shifting Task (SET)(CogState).

Results: Cerebral blood flow was successfully manipulated, with MCAv not different between ISO or PKC at baseline (ISO:57.4±10.4, PKC:58.5±10.4 cm·s-1) but different at hyperthermia (ISO:51.7±5.2, PKC:45.1±7.8 cm·s-1). TBT errors significantly (p=0.04) increased with hyperthermia, but with no significant differences between ISO or PKC at either baseline (ISO: 1.5±1.6, PKC: 1.1±0.7 errors) or hyperthermia (ISO:3.4±2.4, PKC:4.2±2.6 errors). SET errors (p=0.02) increased with hyperthermia, but with no significant differences between ISO and PKC at either baseline (ISO:20.3±6.3, PKC:22.4±8.2 errors) or hyperthermia (ISO:22.4±8.2, PKC:26.2±6.4 errors). SET speed did not change with hyperthermia (p=0.33).

Conclusions: The maintenance of MCAv was unable to counteract the hyperthermia-induced decrements in working memory and executive function, suggesting that altered cerebral blood flow is not the primary cause for mental decrements with hyperthermia.

The effects of local thermal manipulations on motor unit properties during light and moderate contractions

ABSTRACT. Introduction: Muscle temperature has a direct effect on the contractile and metabolic properties of muscle. In many experimental designs, submaximal workloads are determined from maximal force during thermoneutral, such that relative intensity may vary with muscle temperatures. We investigated how different muscle temperature affected motor unit properties with contractions performed at the same normalized percentage of maximal force during each temperature condition.

Method: Ten males and females completed evoked, maximal and trapezoidal voluntary contractions during thermoneutral-, hot-, and cold-muscle conditions on separate days. Forearm muscle temperature was controlled using 25-min of neutral (~32°C), hot (~44°C), or cold (~13°C) water circulated through a tube-lined sleeve. Motor unit properties were assessed during trapezoidal contractions to 30% and 60% force using surface EMG decomposition.

Results: Changes to contractile properties from muscle heating and cooling were evident in the twitch duration, rate of force development, and half-relaxation time, suggesting that muscle temperature was successfully changed (all P<0.05). Further, differences in flexor carpi radialis surface EMG root-mean-square amplitude and mean power frequency between temperature conditions also support muscle temperature changes. Maximal force was not different between neutral and hot (P>0.05) but decreased in the cold (P<0.05 vs both). For both the 30% and 60% contractions, motor unit action potential amplitude and duration was larger and longer in the cold compared to neutral and hot (P<0.05). As expected, the relationship between motor unit firing rate and recruitment threshold indicated by the slope and y-intercept was different between the normalized 30% and 60% contractions (P<0.05 vs both). However, these relationships did not alter across muscle temperatures (slope and y-intercept P>0.05).

Conclusions: Local muscle cooling decreased maximal force, whereas heating altered contractile properties of the muscle. However, when ramp contractions are normalized to maximal force of the respective temperature condition, the motor unit recruitment strategies remain similar.

An Investigation of Temperature Sensing Textiles for Skin Temperature Measurement during Sub-maximal Exercise

ABSTRACT. Introduction: Skin temperature (Tsk) is an important factor in understanding the complex nature of human thermoregulation, the effects of heat strain, and its impact on human performance. At present, most Tsk measures are impractical or unable to be used during competition. We have developed an advanced textile capable of measuring temperature that can be incorporated into clothing. The aim of this study was to validate these newly developed electronic yarns (e-Yarns) against a skin-mounted thermochron (iButtons). Method: Data from 37 individual e-Yarns from 6 participants were analysed. iButtons were positioned using the ISO-standard 8-point method and 6 e-Yarns were embroidered into existing tri-suits at corresponding locations. Participants completed an incremental exercise test commencing at 95W, increasing by 35W every 3 minutes. Tsk was recorded throughout the test and e-Yarn temperature calculated in response to changes in electrical resistance. Additional experiments were conducted with the e-Yarns exposed to a sodium chloride solution (NaCl, range 0 – 342 mmol.L-1) to determine the impact of sweating on the resistance and conductivity. Results: There was a weak correlation between temperature data from the e-Yarns and iButtons (r = 0.345; p= <0.001). Overall, there was a small positive bias with a large systematic error (0.148 ± 6.093, 95% LoA -11.8 to 12.1). There was no difference between the control and insulated e-Yarn temperatures at a NaCl concentration of 0 mmolL-1 (24.8 ± 0.6; 24.6 ± 0; F (7)= 0.0204; p= 0.667, respectively) however, differences were apparent at all other NaCl concentrations (p= <0.01). Conclusions: Tsk may be measured using current e-Yarns at rest if there is good contact between the e-Yarn and skin. However, their accuracy is limited when a sweating response is present. The appearance of NaCl has a clear impact on the resistance of the e-Yarns, rendering them inaccurate and highly variable.

Coupling of Thermal Manikin Newton with Fiala-based Thermophysiological Model

ABSTRACT. Introduction: The manikin control allows to integrate thermophysiological features to a thermal manikin. The review of A. Psikuta from 2017 described state-of-the art solutions of manikin control by thermophysiological model. In this paper, we present a coupled system formed by thermal manikin Newton and Fiala-based model FMTK. Method: The coupling interface operating in real time has been established in Matlab. Manikin is controlled by FMTK using calculated skin temperatures, which are set to the manikin software. Based on these set temperatures, manikin measure heat fluxes, which are going back to the model to substitute a calculation of sensible heat losses. The coupling was tested in the climatic chamber for a standing manikin, air speed 0.1 m/s and different ambient temperatures and metabolic rates: • passive system: 30 °C (nude) • active system: 5 °C, 10 °C, 28-18-28 °C, 28-33-28 °C, 18-42-18 °C, 3-5-8 met (just briefs) and 28-18-28 °C (summer clothing: T-shirt, trousers) Results: Generally, all test cases confirmed that in cold, neutral and warm conditions the coupling is functional. The Figure 1 demonstrates limits of the coupling for hot environment (42 °C), when the coupled system was not able to operate properly after time 120 min, because of time delay in manikin control during transient change (blue vs orange line). The difference between the virtual simulation (grey line) and coupling (blue line) during transient changes was caused just by delay of ambient temperature regulation inside the climate chamber, and it is not an error of the coupled system.

Figure 1. Conditions: 18-42-18 °C, for standing person in briefs Conclusions: The coupling of FMTK with Newton manikin was developed, which allows to operate manikin with considering human thermophysiology. However, in our case was not possible to use it for the hot conditions, because our Newton manikin has no ability to cool down by sweating.

Requirements on microclimate cooling by enhanced evaporation in thermal insulating protective clothing

ABSTRACT. Introduction: The need to wear thermal insulating protective clothing (firefighters, chemical industry, military etc.) is increasing. As sweat evaporation is restricted these garments cause heat stress resulting in reduced work performance and the risk of heat illnesses. A potential relief is the improvement of sweat evaporation via microclimate cooling. This paper focusses on the requirements for such a microclimate cooling method.

Method: In two studies (I+II) male volunteers in protective overalls performed balanced repeated measures within-subjects design tests in a climatic chamber (25°C, 50%RH, 0.2m/s wind speed). They were exposed to work-rest schedules (3 km/h, 5% incline) with insufflating dry air continuously (130min) into the microclimate of an additional air-diffusing garment layer (I: 600 l/min,<<5%RH, 25°C, n=10) or only during breaks (II: 105min of 205min, 600 l/min, <<3%RH, 30°C, n=12). Control conditions (I+II) contained no microclimate cooling.

Results: An essential thermal relief was achieved compared to the non-ventilated conditions: HRmax (M±SD): 123±12 vs. 149±24b/min, n=10, p<0.01 (I). HR in 205.min: 88.5±7.3 vs. 140.2±7.1 b/min, n=4, p<0.01 (II). Without ventilation in breaks (II, control) only 4 subjects tolerated the heat stress. The minima of mean skin temperatures (I: 33.4±1.0°C; II: 33.2±0.8°C) gave no evidence for a counterproductive peripheral vasoconstriction in consequence of ventilation.

Conclusions: Sweat evaporation is the most effective way of heat dissipation. A supporting microclimate cooling method can considerably reduce the disadvantages of commercial devices using ambient air (e.g. wet-hot climates) by optimizing the specific distribution (local sweat glands/rates) of a sufficient amount (600 l/min) of dry air for sweat evaporation in the microclimate of working man. While ventilation temperature has not only an effect on moisture absorption but also on peripheral vasoconstriction and heat transfer by convection a temperature of 25–30°C has proved to be appropriate. The application of this microclimate cooling method appears promising.

Body Mapping of Skin Temperature Profiles during Exercise in Children

ABSTRACT. BACKGROUND: Mapping skin temperature (Tsk) and sweat-rate patterns has gained interest from academia and industry for applications in clothing design, thermophysiological modelling, and the development of thermal manikins. Studies focussed on males versus females, high versus low fitness, young adults versus elderly, and on the impact of acclimation. No information is to date available on skin temperature distribution in children. This is the focus of the present study. METHOD: Four groups of children were studied; males and females of 9 (n=8/11) and of 13 (n=11/9) years old. They performed 45-minutes of treadmill exercise (23℃; 50%RH; 2 m.s-1 wind) (3x15 minutes periods, alternating one-minute run, one-minute walk with Infra-red pictures taken in between each period). Heart rate (target 65-75% HRmax average over whole exercise), whole body sweat rate and tympanic temperature were collected. Each group’s Infra-red pictures were morphed to a reference shape and mean, and median temperature maps were calculated (MATLAB). RESULTS: Before the start of exercise, Tsk was similar for legs and arms in all groups but slightly warmer for the torso in the younger groups. During the run Tsk initially dropped, then stabilised at a lower level before increasing again after the run stopped. Ten minutes after the run, Tsk remained below baseline values. Over the whole period, torso Tsk was higher in the younger groups compared with the older groups. CONCLUSIONS: With equal relative but lower absolute exercise intensity, younger children had significantly higher Tsk than the older ones, mainly on the torso. This was linked to a lower sweat rate in the younger groups, providing less skin cooling and resulting in warmer skin (Tsk as a balance between heat input from blood flow and heat loss by evaporation and convection). Children at age around 9 seem to rely more on dry heat loss than older children. ACKNOWLEDGEMENTS: Funding was provided by ‘adidas future’ sport science.

Agreement between Chest and Mean Skin Temperature: Influence of Clothing Ensemble and Measurement Device

ABSTRACT. Introduction: Physiological monitoring devices commonly employ a single skin temperature measurement location on the chest. This study aimed to measure the agreement between whole-body mean skin temperature and chest skin temperature measured by a conductive or infra-red sensor, wearing two types of clothing ensemble, during exercise in the heat. Method: Twelve males (age: 24.2±3.7y; height: 180±6.5cm; body mass: 82.9±9.5kg; body fat: 16.0±6.5%) volunteered to participate in two trials. Wearing either an athletic (ATH: t-shirt, shorts, shoes) or a chemical protective ensemble (CPE: ATH plus coverall and respirator), participants commenced 30 minutes of seated rest (environment 24°C and 50%) followed by 60 minutes of treadmill walking at 4.5 km∙h-1 and 1% grade (environment 35°C and 40%). Rectal temperature and mean skin temperature (T̅sk, 8-site), chest skin temperature - conductive sensor (iButton) (Tsk-C) and infrared sensor (EQ-02) (Tsk-I), were recorded continuously. Systematic bias and 95% limits of agreement (LoA), accounting for repeated measures, were calculated between T̅sk, Tsk-C and Tsk-I. Results: Rectal temperature rose significantly from rest (ATH: 37.40±0.27°C; CPE: 37.32±0.30°C) to end of exercise (ATH: 37.96±0.21°C; CPE: 38.38±0.43°C), demonstrating significant interaction effects for clothing and time (p<0.001). The elevation in T̅sk from rest (ATH: 33.01±1.18°C; CPE: 33.53±0.74°C) to end of exercise (ATH: 35.90±0.76°C; CPE: 36.46±0.38°C), also showed a significant interaction (p=0.010). In ATH, T̅sk differed from Tsk-C by 1.53±0.57°C (±1.13°C LoA), and from Tsk-I by 2.23±0.84°C (±1.66°C LoA). Wearing the CPE ensemble, T̅sk differed from Tsk-C by 1.11±0.70°C (±1.40°C LoA), and from Tsk-I by 1.76±0.68°C (±1.33°C LoA). Conclusions: Skin temperature measured on the chest overestimates whole-body mean skin temperature. The overestimate was greater for an infrared compared to a conductive temperature sensor, and in the ATH ensemble. These findings should be considered when monitoring skin temperature on the chest and using the data to calculate real-time indices of physiological strain.

Commercially available cooling systems can extend work time in gas-tight protective clothing.
PRESENTER: Ian Stewart

ABSTRACT. Introduction Gas-tight protective clothing requires the use of self-contained breathing apparatus and are completely encapsulating. Extended work duration and/or working in a warm environment can result in the wearer developing heat strain; as the potential to lose heat through normal thermoregulatory mechanisms is diminished or completely removed. Commercially available cooling systems have been touted as a means to extend work durations without heat strain developing. The purpose of the present study was to evaluate internal, external, passive and active cooling systems’ capabilities to extend work time in wearers of gas-tight protective clothing.

Methods Eight males (24±3 yr, VO2max 50.6±4.3 wore an encapsulating suit (Trellchem VPS, Ansell Protective Solutions, Sweden), respirator, safety helmet and a full gas cylinder. Combined ensemble weight 20.2 kg. Participants walked for a maximum of 120 minutes at 4.5 km.h-1, 1% gradient in 35 °C 50 % relative humidity. In a randomised order, participants completed the trial with: no cooling (CON); an ice-based cooling vest (IV); an ice slushy consumed before, combined with IV (SLIV); compressed air circulated through the suit at 2 L.min-1 (AIR); and a battery-operated water-perfused suit (WPS). Mean with 95 % confidence intervals are presented.

Results Compared with CON (28.1 min [23.2, 33.1]), work time was improved with the addition of the WPS (+7.75 min [3.75-11.75], p=0.034), IV (+7.00 min [3.00-11.00], p=0.012) and SLIV (+9.63 min [5.63-13.62], p=0.002), but not with AIR (+1.25 min [-2.75-5.25], p=0.420). There was no difference in performance between the WPS, IV, or SLIV.

Conclusion Apart from the circulating of compressed air (AIR) all cooling systems extended work duration. The combination of internal slushy with the passive external ice-vest extended work duration but not more than the ice-vest alone, indicating the extra time required to administer the slushy may not be advantageous.

Human white-fat thermogenic capacity evaluation via experimental and meta-analysis studies
PRESENTER: Petros Dinas

ABSTRACT. Rationale: Exercise may increase thermogenic capacity of white adipose tissue (WAT), which could subsequently enhance energy expenditure and body weight loss. We aimed to identify browning of human WAT due to exercise by measuring both the uncoupling protein 1 (UCP1) mRNA and protein concentrations. Our approach based on both an experimental study and a systematic review and meta-analysis to confirm the results of the experimental study rather than made conclusions based on previous selected studies. This approach revealed differences between studies conducted in humans and those conducted in animals. Method: We conducted one human experimental study and one systematic review and meta-analysis that included both studies conducted in humans and animals – PROSPERO registration (CRD42019120213). Results: An 8-week exercise program had no effect on both UCP1 mRNA and protein concentrations of human WAT as well as on body composition. Our meta-analysis also revealed: a) no effect of chronic exercise on human UCP1 mRNA; b) a main effect of chronic exercise on UCP1 protein concentrations (Std-md=0.59, CI=0.03-1.16, p=0.04) and UCP1 mRNA (Std-MD=1.76, CI=0.48-3.04, p=0.007) in WAT of normal diet animals; c) a main effect of chronic exercise on UCP1 mRNA (Std-md=2.94, CI=0.24-5.65, p=0.03) and UCP1 protein concentrations (Std-MD=2.06, CI=0.07-4.05, p=0.04) in WAT of high-fat diet animals. Conclusions: Chronic exercise had no impact on both UCP1 mRNA and protein concentrations of human WAT, while in animals it increased UCP1 independently of their diet. In this regard, for the first time we confirm that the available evidence from studies conducted in animals may not be applicable in humans. This should be taken into consideration in future research.

Use of a Portable Metabolic System to Revise Shipboard Work/Rest Guidance in the US Navy

ABSTRACT. INTRODUCTION: Work/rest instructions have provided safety guidance from environmental or work load intensity in civilian and operational military scenarios for over 70 years with little revisions since their development. The US Navy uses the Physiological Heat Exposure Limits (PHEL Curves) developed in the 1960’s and based on a predicted metabolic work load, to provide shipboard heat exposure guidance. Current technology is now available that allows metabolic data assessment in field settings.

METHOD: Twenty-five personnel (age: 23 ± 3 yrs, height: 169 ± 10 cm, weight: 79.4 ± 14 kg) had their VO2 measured each minute while performing their actual shipboard duties for approximately three hours on two separate days (T1 and T2). T1 and T2 values were averaged to provide a single VO2 value. Shipboard personnel from the following work spaces were evaluated in this pilot study: Flight Deck, Hangar Bay, Scullery, Galley, Waste Management, Catapult, and Reactor Room.

RESULTS: Navy-predicted work rates (WR) of scullery personnel (n=8) were significantly higher from the measured WR (240 ± 22 vs 227 ± 28 watts; p = .03). The predicted versus measured WR of non-scullery personnel (n=17) followed the same trend to overestimate the WR (213 ± 36 vs 197 ± 17 watts, respectively). However, this difference was not statistically significant (p = .06), most likely due to a greater variability among the differing work space personnel.

CONCLUSIONS: Findings from this pilot study indicate that differences between predicted and actual WR exist. The ability to measure actual VO2 data provides an opportunity to update guidance that may have become antiquated due to modern technology, protective clothing, and work place methodologies. This has implications for enhancing guidance in civilian and military work environments. Findings from this evaluation have resulted in further efforts to revise the U.S. Navy’s shipboard PHEL curve guidance.

Physiological and Perceptual Markers of Performance During a Military Cold Water Immersion and Rewarming Exercise

ABSTRACT. Introduction: Warfighter readiness is a fundamental component of an effective military force. In harsh environments, such as immersion in cold water, warfighter readiness can be undermined due to physiological and cognitive deterioration. Efforts to maintain readiness in such conditions, therefore, are of critical importance. The current work evaluates relationships between temperature perception, shivering sensation, and mean skin temperature (Tmsk) as markers of cognitive performance during cold water immersion and rewarming. Method: Thirteen military personnel (age: 29 ± 5 yrs, ht: 172 ± 23 cm, wt: 81.8 ± 9.7 kg) participated in cognitive testing during a cold (1°C) water immersion and rewarming exercise. Cognitive testing consisted of tablet-based simple reaction time (SRT) and match-to-sample (MTS) memory tests, which were administered before, during, and after immersion, and at three time points during 60 minutes of rewarming. Prior to each cognitive assessment, temperature perception, shivering sensation, and Tmsk were obtained. Relationships between cognitive performance and physiological and perceptual measurements were analyzed using Pearson correlation coefficients (r) with a significance level set at p < .05. Results: Colder temperature perception was associated with longer SRT (r = −0.80, p < .05) and a reduction in correct MTS responses (r = 0.81, p < .05). Greater shivering sensation was also associated with longer SRT (r = 0.91. p < .05), yet no relationship was observed between shivering sensation and MTS performance (r = −0.48, p = .33). Both SRT and MTS performance were not significantly correlated with Tmsk (SRT: r = −0.73, p = .10; MTS: r = 0.79, p = .06). Conclusions: Findings suggest a possible link between cognitive performance and cold perception (temperature and shivering), which has relevance to warfighter readiness. Future work should focus on interventions that improve aspects of cold perception, which may enhance cognitive performance and improve warfighter readiness.

Applying immersion guidelines to military waterborne movements

ABSTRACT. Introduction: Military waterborne activities include boat travel, river crossings, and navigating through wetlands, with risk for hypothermia due to cold air exposure (CAE) and cold water immersion (CWI). Immersion guidelines are intended to limit core temperature (Tc) from falling below 35.5°C. This study evaluated this guidance for Ranger School students conducting waterborne movements. Methods: On two occasions (D1, D2), 17 Ranger School students moved from a start point (SP) through a swamp to a river crossing (CP), then through a swamp to high ground (HG). Location (GPS), Tc (ingested capsule), and skin temperatures (Chest, Thigh, Calf, Foot) were recorded. Air (Ta) and water (Tw) temperatures, respectively, were 10°C and 13°C, with waist-deep water on D1, and 14°C and 12°C, with knee to thigh deep water on D2. Results: Duration was 2 h 10 min on D1 and 3 h 5 min on D2. On D1 and D2, respectively, Tc decreased (p<0.05) from SP (37.9 ± 0.3°C; 37.4 ± 0.3°C) to CP (37.2 ± 0.5°C; 37.0 ± 0.5°C) and from CP to HG (36.7°C ± 0.6°C; 36.7°C ± 0.5°C). Chest also decreased (p<0.05) from SP to CP and from CP to HG, while Thigh, Calf and Foot decreased (p<0.05) from SP to CP, with no further change to HG. The lowest Tc at HG was 35.6°C on D1, 35.7°C on D2. Conclusions: Based on Tc response, risk assessments for these conditions were appropriate. Immersion tables currently have categories for knee and waist depths. On D1, Tw and depth suggested a limit of 2 h. On D2, Tw and depth suggested a limit of 1.5 to 2 h (waist-deep) or 5 to 7 h (knee-deep). An intermediate depth between knee and waist is recommended. These are the private views of the authors and are not official US Army or DOD policy.

High-reflectivity paints reduce air conditioning needs of workers in long-haul trucks during the summer

ABSTRACT. Introduction: Occupational heat exposure decreases productivity, causes discomfort and may lead to heat stroke. Due to climate change, occurrence and intensity of heat waves may increase in many regions of the world. Workers in the transportation sector are particularly vulnerable as they are inside vehicles when the temperature is high and the solar irradiance is substantial. Air conditioning is used to reduce the heating load on the vehicle cabins, but it impacts fuel efficiency and tailpipe emissions, which is detrimental for climate change mitigation. Therefore, one needs to minimize the air conditioning load while maintaining a comfortable environment inside vehicles. Method: A virtual testing environment was developed to numerically investigate the thermal loads affecting the cabin of long-haul trucks. Using a lumped approach to represent the vehicle, the air temperature and loads in the cabin were calculated for a typical hot and sunny southern Europe summer day. Considering commercially- available paints used on the cabin external surfaces, we investigated the effect of high- reflectivity paints on the air conditioning load required to maintain comfortable cabin temperatures throughout an entire work day. Results: High-reflectivity paints led to significant reduction on the thermal loads affecting the truck throughout the day. Using paints with optical reflectivity of 0.70 instead of 0.04 on the vehicle body reduced the heat absorbed and transferred to the cabin by 43 % when the sun was at its peak. This implied a 25 % decrease in the air conditioning power to maintain the cabin air at 23 °C. Conclusions: The optical properties of the paint used in vehicles, specifically long-haul trucks, has a significant impact on the power consumption of the air conditioning. By carefully choosing the paint properties, one can passively improve the comfort of transportation workers during summer, but also improve fuel economy and reduce tailpipe emissions.

Development of a Thermoregulation Model Using Medical Image Data and the Finite Element Method

ABSTRACT. Introduction: Advancements in medical imaging present an opportunity to improve human thermoregulatory (TR) model accuracy. The purpose of this study is to develop a human TR model using finite element methods.
Methods: A human torso geometry was derived from medical images of a male, 1.76m, 81kg, and 22.7% body fat. The torso included skin, fat, muscle, and eight internal organs: heart, lungs, bones, etc. The finite element software, COMSOL, was used to create the model and run simulations. Each organ was given basal thermal properties, metabolic rates, and blood flow. TR functions were created to simulate shivering, sweating, and vasoconstriction/vasodilation. Heart and skin temperatures were control variables. Heat transfer within the body included conduction between organs and convection with blood. Heat exchange on skin surface included convection, radiation and evaporation. Convective and radiative values were taken from literature about manikins. Model acceptability was examined by dynamically changing the ambient temperature. Two sets of dynamic environments were used: 30°C(0.5h)/48°C(2h)/30°C(1h) and 43°C(1h)/18°C(2h)/43°C(1h), and results compared to literature.
Results: Comparisons of simulated core/skin temperatures with observed temperatures were reasonable. This was assessed by whether or not the trajectories of simulated skin/core temperatures were similar to observed values. Predicted core temperatures were within 0.6°C of the mean literature temperatures. Predicted skin temperatures were up to 0.8°C warmer. The simulations illustrated similar temperature time course patterns to the literature. Predictions demonstrated the different time course of core temperature patterns between rectal/heart temperatures. Thus, the model can reveal detailed temperature profiles that cannot be obtained with traditional CAD (Computer-Aided-Design) models.
Conclusions: Merging medical image data with the finite element method appears to be a viable approach for human thermoregulatory modeling. Our next step is to apply this TR model to a whole body geometry
Disclaimer: Author views not official US Army or DOD policy

Relationship between respiratory chemosensitivity and hyperthermia-induced hyperventilation
PRESENTER: Keiji Hayashi

ABSTRACT. Introduction: There are large individual differences in hyperthermia-induced hyperventilation, but the factors responsible for this variability remain unclear. There are also considerable individual differences in respiratory chemosensitivity. We hypothesized that there is a relationship between the magnitude of hyperthermia-induced hyperventilation and respiratory chemosensitivity. Method: Twelve male subjects (mean (SD) age 22 (1) years, height 176.1 (4.9) cm, weight 73.7 (6.8) kg) participated in a study testing the above hypothesis. Subjects wore a water-perfused suit that was used to maintain or change body temperature. The temperature of the perfused water was initially set at 33°C at rest and 25°C during exercise, which prevented an exercise-induced rise in body temperature. Thereafter, the water temperature was increased to 38°C to raise body temperature during exercise. Subjects performed a cycle exercise at 90 W. We measured respiratory chemosensitivity to CO2 using a rebreathing method. Respiratory chemosensitivity was evaluated at rest, during exercise without an increase in body temperature (Ex.1), and during exercise with a 1°C rise in body temperature (Ex.2). We then assessed the relationship between the rate of increase in minute ventilation and the rise in body temperature and respiratory chemosensitivity. Results: Respiratory chemosensitivities to CO2 were 2.7 (0.9) L.min-1.mmHg-1 at rest, 2.5 (0.9) L.min-1.mmHg-1 during Ex.1, and 2.5 (1.0) L.min-1.mmHg-1 during Ex.2. There were no significant differences among them. In addition, linear regression analysis showed that there was no significant relationship between the rate of increase in minute ventilation and the rise in body temperature or respiratory chemosensitivity (r = 0.26). Conclusions: These results indicate that respiratory chemosensitivity to CO2 does not relate to hyperthermia-induced hyperventilation.

Standard or myths – claims on accuracy of metabolic rate measurements by ISO 8996 revisited
PRESENTER: Peter Bröde

ABSTRACT. Introduction: ISO 8996 provides methods for the determination of metabolic rate (M) classified in terms of increasing levels of effort ('Screening', 'Observation', 'Analysis', and 'Expertise') and presumed accuracy. We assess those claims for estimating M from heart rate (MHR) at 'Analysis' level, as well as for M calculated from oxygen consumption rate (MVO2) measured by the partial or integral method representing 'Expertise'. Method: We quantified the accuracy of these methods by comparing MHR with MVO2 measured in 373 climatic chamber experiments under different workloads and widely varying heat stress conditions. We further scrutinized factors affecting VO2 kinetics according to ISO 8996 against recent findings from the original literature. Results: MHR considerably overestimated MVO2 due to the rise in core temperature, which concomitantly increased heart rate by approximately 30 bpm/°C resulting in an overall error of 43%. After individually correcting for this bias, the accuracy was 10-15% as stipulated by the standard. Moreover, our data supported the 5% accuracy level for MVO2 with VO2 below 1 L/min according to the partial method. The literature review identified Q10 (~7% increase in M per degree increased core temperature), 'slow component’ (excess VO2 beyond the lactic acid threshold), and EPOC (Excess Post-exercise Oxygen Consumption) contributing to the uncertainty of M to unknown extent. On the other hand, the so-called 'Simonson effect', an increased demand of energy at the start of work erroneously deemed causing underestimation of M by ISO 8996, does not exist. Conclusions: Concerning the ongoing revision of ISO 8996 we propose (i) to include compulsory methods correcting for the thermal component of heart rate, (ii) to eliminate the 'Simonson effect', (iii) to restrict the partial method to the measurement of the oxygen uptake, (iv) to issue a warning against using the integral method without any quantitative estimation of the EPOC effect.

Infrared thermography technique for the assessment of footwear thermal comfort

ABSTRACT. Introduction: Footwear thermal comfort is one of the relevant properties that are taken into account during the evaluation of footwear performance. However, it is difficult to quantify in that it is inherent to the subjective perception of each individual. This work is aimed to implement the infrared thermography technique as part of the protocol for the objective assessment of thermal comfort in footwear at different levels, from the evaluation of the materials by using standard methods to whole shoe assessment in real wearing conditions.

Method: Dynamic IR thermography is a rapid, non-contact and non-invasive technique; measurements are taken at a distance. To measure the surface temperature accurately, parameters such as the distance between the object and the IR camera, relative humidity, atmospheric temperature, apparent reflected temperature and the emissivity of the object must be provided to the camera. The emissivity varies between 0 and 1, according to the properties of the surface and the material and must be determined for each object. The emissivity value of human skin is 0.98. A thermal imaging camera ICI 8320 model P series and IR Flash Pro Image Analysis Software was used. Furthermore, IR thermogram results were correlated with the user’s perception over use obtained by means of validated questionnaires based on a bipolar scale. The correlation obtained depends on the footwear model studied.

Results: A method consisting of several stages was set up. It was based on the dynamic IR thermography technique for the assessment of thermal comfort in different controlled environments. Qualitative results were obtained by checking the thermal images of the footwear and foot areas studied, which were taken right before and after the footwear trials. The overall quantifiable results were drawn by calculating the average temperature increase occurred in the areas under study of the user’s feet and footwear while performing several activities that raise the thermal load.

Conclusions: Through this research, it was possible to appreciate the potential of infrared thermography and the benefits that this technique brings for footwear assessment, in that it is quite useful in identifying the areas that provide the greatest breathability and in choosing footwear that facilitates thermoregulation.

Thermal Burden of a Decontamination Protective Ensemble

ABSTRACT. Introduction: Careful consideration should be given to the heat exchange properties of protective clothing when selecting appropriate systems for the anticipated operational threat. The aim of this study was to assess the thermal burden of a decontamination protective ensemble (DPE) and recommend limits to work duration. Method: The thermal insulation (It), evaporative resistance (Ret), and evaporative potential (im/clo) of an individual protection ensemble (IPE) worn with or without a DPE were measured on a heated sweating manikin according to ASTM standards. The Heat Strain Decision Aid model was used to estimate work durations before a body core temperature of 38.5 °C was reached during personnel and equipment decontamination station activities (PDS 180 W and EDS 280 W) at a Wet-Bulb Globe Temperature of 26 °C. A recovery period of 60-min was modelled to investigate if doffing the DPE facilitated a reduction in body core temperature. Results: Greater restrictions to heat exchange were measured in DPE+IPE (It 2.63 clo, Ret 0.43 kPa∙m2/W, im/clo 0.02) compared to IPE (It 2.21 clo, Ret 0.07 kPa∙m2/W, im/clo 0.13). The time to reach a body core temperature of 38.5 °C was most restricted during the EDS activity wearing DPE+IPE (PDS, 366 IPE vs 116 min DPE+IPE and EDS, 87 IPE vs 65 min DPE+IPE). During the recovery period the predicted body core temperature declined by 0.3 °C if the DPE was doffed. Conclusions: Wearing DPE while performing decontamination is severely restrictive to heat loss thus limiting work durations. Work tables need to be adjusted for the added thermal burden of wearing DPE with considerations made for cooling strategies to reduce the risk of heat illness.

15:30-17:15 Session 17: Manikins and modelling
Modelling of conditioned automotive seats
PRESENTER: Miloš Fojtlín

ABSTRACT. Introduction: Seats play a significant role in the thermal experience because of their large contact area with a human body. The occupant-seat contact area is exposed to the current thermal state of the seat as well as isolated from the ambient microclimate. This situation might be especially critical in vehicular cabins, where the operating conditions can temporarily reach extreme values. To enhance the thermal experience in such circumstances, seat conditioning technologies were developed. On the other hand, a method to calculate boundary conditions at seats for thermo-physiological modelling is not available. The aim of this study is to develop a physical model that realistically solves time-dependent heat exchange between the seat and the occupant.

Method: The model was developed using fundamental heat transfer principles simplified to a one-dimensional problem with dominant heat flux in a perpendicular direction to the seat plane. The computational nodes comprised human tissues as well as adjacent clothing and seat construction layers. The calculated heat fluxes were validated against our own measurements of heat flux by means of RMSD and bias. The tests were carried out in cool (tamb = 18 °C) and hot (tamb = 41 °C) conditions using unconditioned, heated, and ventilated seats and a pool of nine participants.

Results: The results showed good agreement between the experimental and calculated data with respect to the intended model application. The RMSD and bias were typically within two standard deviations of the experiment. Most importantly, the model captures the time-dependent development of the heat exchange, which is considerably different from the static approach – using thermal and evaporative resistances to represent the seat.

Conclusions: The proposed model was shown to realistically calculate heat transfer between the seat and the occupant. This tool can be coupled with thermo-physiological and thermal sensation models to enhance their applicability and accuracy for seated exposures.

New generation of thermal manikin with integrated surface heat flux sensor and active cooling system
PRESENTER: Agnes Psikuta

ABSTRACT. Introduction: Thermal manikins, as the most realistic devices for simulation of heat and mass transfer from the human body, are nowadays implemented in a wide range of disciplines including clothing research, the automobile industry and the building environment research. State-of-art manikins, however, cannot measure environmental heat gain due to lack of active cooling and low thermal capacity compared to humans. The recently developed manikin ANDI (Thermetrics, USA) with active cooling and integrated surface heat flux sensor can overcome these shortcomings. Method: We have evaluated this new type of thermal manikin for its accuracy and applicability to simulate human heat exchange with the environment in steady state and transient conditions, including hot conditions. Results: The evaluation results confirmed the relevance of the new technology for variety of standard and close-to-practice measurements. At the same time, we could demonstrate advantages of this novel manikin over state-of art manikins for simulation of human thermo-physiological response (Fig. 1).

Fig. 1. Exemplary mean skin temperature simulated by manikin ANDI coupled with Manikin PC2 human thermoregulation model (Thermoanalytics, USA) with and without cooling system being active, and compared to human experimental data (Munir et al. 2009, Build & Env). Conclusions: This new generation thermal manikin significantly widens the application range of thermal manikins for not only static measurements (body heat gain in hot environments) but also dynamic simulations of human thermo-physiological response in realistic clothing and environmental scenarios.

Predict Human Physiological Response and Evaluate Thermal Properties for Multi-Temperature Adaptable Smart Clothing: Application of Physiology Model Controlled Manikin and Thermal Conductivity Analyzer in Various Ambient Temperatures

ABSTRACT. Introduction: More and more functional smart textiles have been developed for the purpose of preventing people from suffering heat/cold impacts and fulfilling their needs in transient conditions. However, there are not so many proper test methods been available for these new textiles. The aim of this study is to establish test protocols by using various testing tools to determine the properties of temperature smart textiles and clothing systems. Method: A ThermoreⓇ smart insulation jacket was selected for this study and normal outdoor apparel was chosen as the control sample. All the tests were carried out in a climatic chamber. The thermal effusivity and thermal conductivity of fabrics were determined by using a thermal conductivity analyser, MTPS, in different ambient temperatures (30℃ v.s. 10℃ and 20℃ v.s. 0℃). Furthermore, human thermal comfort was evaluated by using the physiological and comfort manikin (MPC) in static and dynamically changing environments. The test consisted of the following four periods: 1) 1 MET activity level at 20℃ (15 min), 2) increase activity level to 2 MET (15 min), 3) lower down ambient temperature to 10℃ (90 min), 4) decrease activity level to 1 MET at 10℃ (30 min). The major measurements include rectal temperature, skin temperatures (Tsk), perceived thermal sensation, comfort, and dynamic thermal sensation (DTS). The analysed items also include regional differences and cooling rates between ambient and skin temperature. Results: The repeatability of all the tests was assessed by calculating the mean absolute deviation (MAD). The average MAD between the 6 parameters was in the range of 0.01 and 0.22. The maximum MAD was found in DTS, which was less than 0.75. On the other hand, the % Change of thermal effusivity of the test sample was analysed by comparing the results under different ambient temperatures, which were 12.33% and 9.25% respectively. The results showed that comfort rating was around 2 (comfortable) at temperature smart jacket covered segments, around -2 (uncomfortable) at control sample segments, and around -3 (very uncomfortable) at control segments, e.g. bare hand. Furthermore, the highest cooling rate of ambient temperature was 17.99 °C.h-1 at the 3rd stage of MPC test, but instead, Tsk showed relatively stable through all the test periods. Conclusions: In this study, several test protocols have been designed to determine the properties of functional smart textile materials, fabrics, semi-product, and clothing system. The established evaluation items include the thermal effusivity of fabrics and the physiological and comfort evaluation technology for temperature adaptable smart clothing systems. The results showed that MTPS and MPC can be used as testing tools to distinguish the thermal properties of temperature adaptable fabrics and the performance of temperature adaptable smart clothing systems in various ambient temperatures. Nevertheless, further validation study is needed to compare results of MPC with human subject trial for temperature smart clothing in these transient conditions.

Thermal Manikin Comparison of Cooling Methods

ABSTRACT. Introduction: Military readiness depends on rigorous military training, however intense training can lead to exertional heat illnesses (EHI). The medical costs and long-term implications of EHI can force lost training days, impacting unit readiness and individual careers. Each year more than 2000 Soldiers experience an EHI serious enough to require medical attention and/or lost duty time. Though prevention of EHI remains a high priority, rapid and effective treatment remains key. Several field-expedient methods of rapid cooling to reduce EHI severity were tested.

Method: Total cooling power was measured using a Thermetrics (Seattle, WA), Newton 20 zone thermal manikin according to ASTM F2371-16, Standard Test Method for Measuring the Heat Removal Rate of Personal Cooling Systems Using a Sweating Heated Manikin. Environmental conditions were 35°C, 40% RH, and 0.4 m•s-1 wind speed. Performance of iced sheets and ice packs was compared with two commercial cooling products.

Results: When the thermal manikin was covered with bed sheets soaked in ice water the peak cooling was 369 W. Peak cooling for the iced sheet with ice packs on the armpits and groin was 427 W. Peak cooling for CAERvest® (BodyChillz LTD, Gatwick Sussex, UK) and Polar Skin ™ Comprehensive Cooling System (North American Rescue, Greer, SC USA) were 160 and 277 W respectively. Cooling durations of CAERvest® and Polar Skin ™ were 48 and 34 minutes, average heat extraction 55 and 28 W.

Conclusions: Of the methods examined, iced sheets with ice was most effective for rapid heat extraction. It is not always feasible to have coolers full of iced sheets nearby. This study quantified the potential for heat extraction by other methods which may be more appropriate for austere conditions. Since thermal manikin testing does not reflect human physiology, human studies are necessary to further assess cooling potential of various methods.

Citations of commercial organizations and trade names does not constitute an official Department of the Army endorsement or approval of the products or services of these organizations. The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Predicted Heat Strain (PHS) model predicts the evaporative water loss well in an extremely hot climate

ABSTRACT. Introduction: The aim was to study if the evaporative water loss from the body can be predicted enough accurately for hydration recommendations by ISO 7933 – Predicted Heat Strain (PHS) model based on the example of a student laboratory exercise in an extremely hot environment.

Method: Twelve young healthy students (8 males and 4 females), unacclimatized to heat, were exposed in a climatic chamber at 50˚C, 30% relative humidity and 0.4 m·s-1 air velocity for 45 minutes. They had a mean (SD) age of 25.1 (2.6) years, height 175.6 (6.9) cm, weight 72.3 (11.0) kg, VO2max 54.9 (6.5) mL·min-1·kg-1, and HRmax 194 (6) bpm. The men and women performed bicycling for 6-minutes at workloads of 150 and 100 Watts (W), respectively. The calculated metabolic rates (M) for biking at 150 and 100 W were 363 and 290 W·m-2, respectively. Moreover, the subjects did step test at 60 steps·min-1 for 5-minutes with estimated M being 215 W·m-2. Most of the time (34 min), they were standing with some movements (M = 80 W·m-2). Time weighted average M for males and females were 133 and 123 w·m-2, respectively, for the whole duration of exposure. Clothing insulation, Icl = 0.4 clo and moisture permeability index, im = 0.42 were input to PHS model simulation. The actual water loss by evaporation was determined by subject’s dressed body weight difference before and after exposure (sports clothing and Polar pulse belt with transmitter).

Results: The actual mean (SD) total water evaporated was 461.3 (176.7) g after 45 minutes. The predicted total water loss was 427.4 (39.2) g by the PHS model. There was no significant (p = .514) difference between the actual and the predicted water loss.

Conclusions: PHS model appears to be reliable to foresee the evaporative water loss in continuous short-term exposure at 50˚C in young healthy students. The results suggest that ISO 7933 – PHS model is a useful tool to predict the risk of dehydration and plan for drinking in extremely hot climates.

Realistic clothing model for heat and moisture transport through human skin-clothing-environment system
PRESENTER: Ankit Joshi

ABSTRACT. Introduction: Heat and moisture transport from human skin to the environment is a critical aspect for protective and functional properties of clothing as well as thermal sensation and wearing comfort. The simulation of heat and moisture transport in clothing is a time-efficient and inexpensive approach to the virtual design of clothing and thermally comfortable and safe environment for human occupancy. The current models oversimplify enclosed air layers by assuming its homogeneous distribution which causes significant errors in simulated heat fluxes. In this study, we investigated the validity of heat and moisture transport through realistic heterogeneous air gaps, along with the effect of the body movement, ventilation through opening and porosity of the fabric.

Method: The newly developed model considers several heat and moisture transport mechanisms, such as conduction, forced and free convection, radiation, evaporation, condensation and wet conduction. It was systematically validated through more than 30 cases with an increasing level of complexity for the wide range of conditions including static and dynamic (caused by human movement) air gap distribution.

Results: The developed model is validated for the sensible and latent heat flux including effect of ventilation due to wind and movement as well as evaporation and condensation in clothing layers. The model showed good agreement with measured data with an average relative error of 12%.

Conclusions: The presented clothing model was proved to be accurate and robust and can be useful for several research fields, where the analysis of the interaction between thermal environment and the human body is in focus.

Evaporative resistance calculations analysis based on pre-wetted thermal manikin measurements
PRESENTER: Róbert Toma

ABSTRACT. Introduction: The aim of this study was to test previously published corrections for calculating clothing evaporative resistance (Ret) by heat loss method on dry thermal manikin using sweating system with pre-wetted skin. The main objective was to investigate to what extent are these corrections usable for this sweating system as many of them were proposed based on manikins with different sweating simulation systems. Method: Dry thermal manikin TORE at Lund University with pre-wetted skin was used to measure 14 clothing ensembles composed of Taiga AB (Sweden) ambulance system garments covering range from 0.63 to 3.33 clo. Evaporative resistance (Ret) was measured in a standing posture with air velocity of 0.5±0.1 m/s to manikin´s back and ambient temperature with relative humidity controlled at 34.0±0.1 °C and below 40 % respectively. Evaporative resistance was simultaneously measured by both mass loss method using weighting scale (Mettler Toledo K240) and heat loss method using thermal manikin software. Paired two-tailed t test was used to compare 8 different calculation methods using various corrections based on heat loss measurements with values calculated by mass loss method, which should be correct from physical point of view. Insulation-based analyses was also concluded, and the same t test was done for insulation intervals of 0-2.0 clo, 0-2.5 clo and 2.0-3.5 clo. Results: The statistical analysis with level of significance set at 0.05 for whole range of clothing insulation shows that there is no significant difference between the values calculated by mass loss method and 6 different calculating methods using various corrections for heat loss method. In insulation-based analyses, corrections with significant difference where changing with changing thermal insulation intervals. There is also a difference in results when the same analysis was conducted on basic evaporative resistance (Recl) instead of total evaporative resistance (Ret). Conclusions: Some of the heat loss method corrections could be omitted from statistical perspective while using pre-wetted skin. Further research is needed to see if these results also apply to other sweating thermal manikins using pre-wetted skin method. Future objective is to see the impact on physiological modelling while using different evaporative resistance values from various calculations to keep good balance between accuracy of the model and complexity of the measurements.

Validation of ISO 9920 clothing item insulation summation method based on an ambulance clothing system

ABSTRACT. Introduction: The aim of this study was to validate the summation method suggested by ISO 9920 based on the example of an available ambulance clothing system. Simultaneously, an objective was to evaluate this clothing system from the viewpoint of the standardized calculation paths for use in the standard models for prediction of human exposure to cold and heat. Method: 28 items from the Taiga AB (Sweden) ambulance system, shoes and gloves were selected for this study. All items were tested individually on the thermal manikin Tore at Lund University according to ISO 9920 requirements (low air velocity), and basic insulation of each garment (Iclu) was calculated. More than 100 realistic clothing combinations were compiled and basic insulation (Icl) of these clothing ensembles was calculated according to ISO 9920. These were ranked after the calculated insulation, and 14 sets were selected to cover evenly a range of insulation values from 0.63 to 3.33 clo. Basic insulation (Icl) of the selected sets was calculated based on thermal manikin measurements. Photographic method was used to estimate clothing area factor (fcl) of the individual garments and the ensembles. Regression analysis was used to compare the estimated and measured basic clothing insulation values. Results: The difference between measured and estimated basic insulation values varied from -18 to 12 %. The highest percentual difference was for the lightest clothing sets. However, when looking on absolute differences, then these were similar over the whole range of tested insulation values ranging between -0.17 to 0.18 clo with an average difference of 0.02 clo (-0.16 %). All basic insulation vales stayed very close to the line of identity (R2 = 0.9775). Conclusions: The equation to estimate basic clothing insulation (Icl) from individual items’ insulation (Iclu) gave, in the case of this ambulance clothing system very close results to the measured values. This encourages evaluating and selecting protective clothing for ambulance personnel based on individual item measurements.