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08:30-10:00 Session 6: Heat acclimation for special populations
Heat acclimation for special populations symposium: Elite populations and preparation for Tokyo 2020

ABSTRACT. Exercise-heat acclimation induces physiological adaptations that improve thermoregulation, attenuate physiological strain, reduce the risk of serious heat illness, and improve aerobic performance in warm-hot environments. The heat acclimation phenotype is generally achieved through four broad induction pathways: constant work rate exercise, self-paced exercise, controlled hyperthermia or isothermic heat acclimation, and the controlled heart rate approach. A key question for elite athletes regarding the implementation of heat training is when to schedule it in the overall training program, and in particular ahead of competing in the heat. Indeed, elite athletes adhere to regimented training programs and traditional heat acclimation regimens require manipulation to ensure that heat exposures are properly programmed into the training cycle, in order to result in optimal benefits. It is therefore imperative to explore the ways in which heat acclimation regimens can be modified (e.g. fragmented and/or combined) to ensure that elite athletes adapt through carefully implemented regimens.

Mixed active and passive, heart rate-controlled heat acclimation is effective for Paralympic and able-bodied triathletes
PRESENTER: Ben Stephenson

ABSTRACT. Introduction: Given the popularity of the Paralympic Games, surprisingly few studies have examined the effectiveness of heat acclimation (HA) for Paralympic athletes thus little information exits regading adaptation differences to able-bodied (AB) athletes. Therefore, the aim of the study was to investigate the efficacy of a novel HA protocol for Paralympic and AB triathletes.

Method: Seven elite paratriathletes and thirteen AB triathletes undertook an 8-d HA intervention consisting of five, HR-controlled sessions and three passive heat exposures (35oC, 63% relative humidity). On the first and last day of HA, heat stress tests were conducted whereby thermoregulatory changes were recorded at a fixed, submaximal workload. The AB group undertook 20 km cycling time trials pre- and post-HA with performance compared to an AB, non-acclimated control group.

Results: In both groups, HA resulted in lower core temperature (~0.3oC), blood lactate concentration (~0.3 mmol∙l-1), and perceptual improvements with concomitant plasma volume expansion (6.2-12.7%) (p≤0.047). In the HA group, a lower skin temperature (0.58oC) and HR (5 bpm) with a greater sweat rate (0.17 l∙h-1) was evident post-HA (p≤0.045) but this was not present for the paratriathlon group (p≥0.177). The AB group improved their performance by an extent greater than the smallest worthwhile change based on the normal variation present with no HA (4.5 vs. 3.7%).

Conclusions: Paratriathletes are capable of displaying partial HA, albeit not to same extent as AB triathletes. The HA protocol used was effective at stimulating thermoregulatory adaptations with performance changes noted in AB triathletes.

Adaptation to the heat using short-term acclimation with dehydration in matched females and males

ABSTRACT. Introduction: Short-term heat acclimation (STHA) with dehydration, has been reported to improve adaptations and performance during heat exposure but have tended to use male participants. Therefore, the aims of this work were to investigate STHA over 5-days (permissive dehydration), using the controlled-hyperthermia technique, with a matched female and male cohort. Method: Ten, moderately-trained, females (Mean [SD]; age 22.6 [2.7] y; stature 165.3 [6.2] cm; body mass 61.5 [8.7] kg; VO2peak 43.9 [8.6] and ten males (Mean [SD]; age 25.6 [8.9] y; stature 180.7 [5.6] cm; body mass 83.2 [10.8] kg; VO2peak 45.3 [6.5] participated in a STHA programme. This consisted of 90 mins dehydration (no fluid intake), heat acclimation for 5-consecutive days (39.5oC; 60%rh), using the controlled-hyperthermia technique (~rectal temperature [Tre] 38.5oC). A number of blood plasma constituents were measured: percent plasma volume (%PV), aldosterone, total protein, albumin, Na+, K+, Cl-, cortisol and HSP70. Pre and post STHA, a gender-specific, heat stress test (HST) (35oC; 50%rh) was performed consisting of 45-mins of intermittent exercise and a repeated, maximal sprint performance test. The HST was specific to exercise intensities of professional football players for females and males. Results: Pre vs post HST there was a reduction in Tre at 45-min in females by -0.20°C (95%CI -0.30 to -0.05°C; P=0.01; ES=1.13) and males (-0.20: -0.40 to -0.05°C; P=0.03; ES=-0.56). Cardiac frequency decreased in females by -3 b.min-1 at 45-min (-10 to 3 b.min-1; P=0.06, ES= 0.64) and males (-3: -5 to -1 b.min-1; P=0.01; ES=-0.20). In females there was an increase in mean average power across maximal sprints by 56W (-26 to 139W; P=0.03; ES=0.69) and males (87: -8 to 182 W; P=0.05; ES=0.52). Conclusions: Short-term heat acclimation (5-days) with dehydration, using the controlled-hyperthermia technique, is effective for physiological adaptations during intermittent exercise in a hot environment for matched females and males.

Examining the effects of short-term heat acclimation on markers of thermotolerance in young and older healthy adults

ABSTRACT. Introduction: Heat acclimation (HA) reduces the thermoregulatory stress and consequently delays the risk of heat illness during heat stress. Evidence suggests heat shock proteins (HSPs) are contributors to heat adaptation at a physiological and cellular level and are key markers of thermotolerance. Specifically, Hsp72 and Hsp90α have been used as markers of the cellular response to stress The aim of this study was to explore the effect of short-term heat acclimation (STHA) on leukocyte Hsp72 and Hsp90α mRNA response in the elderly population compared with young individuals.

Method: Nine, active younger (Y) individuals (Mean [SD]; age 22.2 [1.9] years; height 177 [0.05] cm; mass 75.4 [11.47] kg; 1 female) and six, active older (O) individuals (age 66.7 [2.6] years; height 178 [0.07] cm; body mass 76.8 [9.55] kg; 6 males) completed five consecutive days of HA in 35°C/50% R.H. The STHA protocol increased resting rectal temperature (Tre) by 1.5°C or to 38.5°C within the first 60mins and subsequently maintained Tre for a further 60mins. Leukocyte Hsp72 and Hsp90α mRNA responses assessed using reverse transcription polymerase chain reaction (RT-QPCR) were determined within and between the first and final day of HA, with comparisons made between groups using ANOVA.

Results: Resting Tre and heart rate (HR) showed no improvements after STHA in the O group (+0.20±0.21°C, 1±9 b.min-1) but did so in the Y group (-0.21±0.29°C, -6±10 b.min-1). Thermal sensation decreased in O (-0.3±0.4) and Y (-0.3±0.4) with a significant change only in Y (p<0.05). Thermal comfort did not change in the O group (0±1) but decreased in the Y group (1±1). Changes in Hsp72 and Hsp90α mRNA transcription in response to each session in the older and younger group is currently being analysed.

Conclusions: STHA appears less effective in active older individuals compared younger participants given reduced phenotypic adaptation.

Glucose metabolism in overweight men improves after passive heat acclimation

ABSTRACT. Introduction: It has been suggested that certain thermal conditions might have positive implications for metabolic and cardiovascular health. Acute heat exposure has been suggested to enhance glucose metabolism, possibly via an increase of heat shock protein 72 (HSP72) in muscle. This study investigated the effect of a 10-day passive heat acclimation (PHA) intervention on glucose metabolism, thermophysiological and cardiovascular parameters, and muscle HSP72 levels in an overweight population.

Method: 11 overweight men (65.7±4.9y, BMI 30.4±3.2kg/m2) underwent PHA (10d, 34.4±0.2˚C, 4-6h/d). Pre- and post-PHA, fasting plasma glucose and insulin samples were collected to assess glucose metabolism. A temperature-ramp-protocol (28.8±0.15˚C to 41.3±o.33˚C, 10K/h) was conducted to assess thermophysiological parameters (core temperature, mean arterial pressure [MAP] and heart rate), before and after PHA. To assess HSP72-levels, muscle biopsies were taken before and after PHA.

Results: Fasting plasma glucose (FPG), fasting plasma insulin (FPI) as well as core temperature (Tcore) decreased significantly after PHA (∆FPG: 0.27 mmol/L, p=0.036; ∆FPI: -12.69 pmol/L, p=0.026; ∆Tcore: -0.17±0.19˚C, p=0.017). Also, MAP decreased (∆MAP 2.91±2.67 mmHg, P=.007) and heart rate tended to decrease (∆ 2.98±3.50bpm, P=0.065) post-PHA. Mean HSP72 levels in muscle did not change significantly.

Conclusions: Core temperature decreased after passive heat acclimation, confirming the effectiveness of the applied acclimation protocol. We show that passive heat acclimation beneficially affects glucose homeostasis, denoted by changes in fasting plasma glucose and insulin levels. Reduced mean arterial pressure and heart rate indicate that heat may positively affect cardiovascular health. HSP72 in muscle was not affected by this heat acclimation protocol. Together, results encourage further research to explore the underlying mechanisms.

10:30-12:00 Session 7: Heat acclimation
Differential effects of short-term heat acclimation on whole-body heat loss in middle-aged males with and without type 2 diabetes

ABSTRACT. Introduction: Aging reduces whole-body evaporative heat loss (EHL) and exacerbates body heat storage in middle-aged compared to young adults during exercise-heat stress. This maladaptive response is worse in middle-aged individuals with type 2 diabetes (T2D). While short-term heat acclimation can enhance heat dissipation in middle-aged adults, it remains unclear if the magnitude of improvement differs in individuals with T2D. Methods: We therefore used direct calorimetry to assess EHL prior to (day 0) and following (day 8) seven days of heat acclimation (90-min cycling at 50% peak aerobic power (V̇O2peak)) in dry-heat (40°C, 20% relative humidity) in middle-aged (mean±SD; 60±6 years), physically active (V̇O2peak: 35.2±6.5 males with (n=8, HbA1c: 6.9±1.0%, duration of T2D: 10±7 years) and without (Control, n=10) T2D matched for age and V̇O2peak. On days 0 and 8, participants performed three 30-min bouts of cycling at metabolic heat productions of 150 (light), 200 (moderate) and 250 W.m-2 (vigorous) (equal to 37±6, 49±8, and 61±9% of V̇O2peak, respectively), each followed by 15-min recovery, in dry-heat (40°C, 15% relative humidity). Results: EHL increased following acclimation in T2D (day 0 vs. day 8; light: 179±25 vs. 192±22 W.m-2, moderate: 216±25 vs. 239±25 W.m-2, vigorous: 242±29 vs. 279±27 W.m-2; all P<0.05) and Control (light: 185±11 vs. 198±21 W.m-2, moderate: 237±16 vs. 254±16 W.m-2, vigorous: 276±26 vs. 294±19 W.m-2; all P<0.05). The magnitude of that increase was similar between groups during light and moderate exercise (both P>0.05), averaging 7±7% and 9±5% across groups, however it was greater for T2D during vigorous exercise (Control: 7±6%; T2D: 16±7%, P=0.01). Conclusions: Our preliminary findings demonstrate that the magnitude of improvement in whole-body EHL during a short 8-day heat acclimation intervention is greater in middle-aged males with well-controlled T2D compared to their healthy counterparts during vigorous exercise in the heat. Funding: Canadian Institutes of Health Research.

Dosed intensity of heat strain for adaptation in passive heat acclimation
PRESENTER: Jamie Prout

ABSTRACT. Rationale Passive heat acclimation (HA, without exercise) elicits cardiovascular, thermoregulatory and muscular adaptations, and can be especially useful for those with limited exercise capacity. Such people may be less tolerant of heat-strain intensities that typify HA (core temperature (Tc) >38°C). Cardiovascular adaptations are key aspects of HA, and cardiovascular responses to heating saturate at modest heat strain. The purpose of this study was to further identify the heat-strain dose:adaptation relations of thermoregulatory and cardiovascular adaptations to passive HA.

Methods Nine recreationally-active participants (23 ± 4 y; 4 female) completed three spa-bath HA regimens in cross-over fashion: Tc was clamped at baseline in water (NEUT) on six days, or elevated by +0.75 °C (WARM) or +1.5 °C (HOT) on nine days. Exposures were 60-min⋅d-1 immersed in water, with thermal strain controlled using depth and water temperature (36.5, 38.5 and 40.5 °C). A heat stress test was conducted on days 1, 5, and 9 in WARM and HOT, and one week prior and on day 6 for NEUT; involving nipple-depth immersion in 40 °C water. Regimens were 6-wk apart.

Results No dose effect was evident for the adaptation in resting plasma volume or stressed heart rate, sweat rate, thermal sensation, discomfort or affect (interactions: p = 0.11 to 0.98). For example, the expansion in resting plasma volume (p < 0.01) was similar (p = 0.98) across HOT (3 ± 7%), WARM (3 ± 4%) or NEUT (3 ± 6%). Resting Tc was reduced (p < 0.01) but not reliably more across HOT (-0.25 ± 0.16 °C) than WARM (-0.19 ± 0.16 °C) or NEUT (-0.03 ± 0.21 °C, p = 0.11).

Conclusion There was minimal evidence to show greater heat dose led to greater adaptation during passive HA.

Daily cold-water recovery may impair training load tolerance during short-term heat acclimation

ABSTRACT. Introduction: Currently, there is limited understanding of the effects of heat acclimation (HA) on perceptual training load (TL) or the interaction with common thermal recovery strategies. This study aimed to examine the effects of daily cold- and hot-water recovery on perceived TL during short-term HA training. Methods: Eight healthy, trained males undertook 5-days of cycle training for 60 min in four different conditions, using a block counter-balanced order design. Three conditions were completed in the heat (35 °C) and one in a thermoneutral environment (24 °C, CON). Each day after cycling, participants’ completed recovery 20 min seated rest (CON and HA), cold- (14 °C; HACWI) or hot-water immersion (39 °C; HAHWI). Heart rate, rectal and skin temperature, and rating of perceived exertion (RPE) were collected during training. Session RPE (sRPE) was collected after training for the determination of perceived TL. Data was analysed using Bayesian hierarchical regression, Cohens d was calculated, and for perceived TL, the probability that d >0.5 was also computed. Results: Bayesian analysis showed evidence of increased perceived TL in HACWI compared to HA on days 3–5 (d=2.26-2.69). The probability that the d >0.5 for days 3, 4 and 5 were 0.98, 0.98 and 0.96, respectively. There was evidence that the increased perceived TL coincided with a greater exercise heart rate (3–8 b·min-1 higher; d=2.34-3.00) and higher RPE on days 4 (d=2.46) and 5 (d=2.27). There was little evidence that hot-water altered perceived TL or heat adaptation. Conclusion: Daily cold-water recovery increases percevied TL, interefers with heat adpatation, and impairs TL tolerance during 5-days of fixed-intensity HA, and hot-water immersion provides no additional benefit. Considerations for the effects of thermal recovery strategies on TL are required when implementing to avoid counteracting the desired HA outcomes.

Short-term heat acclimation training enhances knee extensor strength and improves cyling performance in hot conditions

ABSTRACT. Introduction: The redistribution of blood flow from splanchnic regions during exercise in the heat may compromise gastrointestinal permeability and facilitate endotoxin leakage. Subsequent inflammatory responses are suggested to cause neuromuscular fatigue. This study examined the protective neuromuscular and inflammatory effects of short-term heat acclimation (HA) on cycling performance in the heat. Methods: Eight recreationally-trained males completed a 5-day cycling training block (60 min∙day-1 at 50% Pmax) in hot (HA: 35±1 °C, 53±4% relative humidity (RH)) and thermoneutral (CON: 22.2±2.6 °C, 65±8% RH) conditions using a randomised cross-over design. Pre- and post-intervention TT’s were completed in the heat. Neuromuscular assessment of the knee extensors was completed pre- and immediately after the TT’s and on the first and last day of each training block. Blood samples were also collected at these same time points and analysed for endotoxins, inflammation and markers of gut damage. Data were analysed using Bayesian hierarchical regression, and Cohens d effect sizes were also calculated. Results: Statically faster TT completion times was apparent after HA compared to CON (MD=55s [11, 98], d=2.51 [0.49, 4.46]). While pre- to post-intervention improvements were observed in HA (MD=62s [18, 104], d=2.86 [0.82, 4.75]), no clear difference was seen in CON (MD=30s [-6, 67]). Interestingly, knee extensor strength increased with HA but declined in CON. Further, despite the faster post-intervention HA TT performance, no difference was found for central fatigue, circulating endotoxin levels, inflammation, or markers of gut damage between conditions. Conclusion: Short-term HA training improves subsequent 20TT cycling performance in the heat by 2.9% [0.8-4.9] without an associated increase in intestinal damage or inflammation. These findings suggest that short-term HA training may be a time-efficient training method to improve neuromuscular function and cycling performance in hot conditions.

The Physiological and Perceptual Adaptations to an Isothermic Short and Medium-Term Heat Acclimation Protocol

ABSTRACT. Introduction The aim of the present study was to investigate the effect of short (STHA) and medium-term (MTHA) isothermic-controlled (ISOCON) heat acclimation (HA) on the physiological and perceptual responses to exercise heat stress.

Methods Sixteen, non-heat acclimated, ultra-endurance runners visited the laboratory on 13 occasions. A heat stress test (HST) was completed on the 1st (HST1), 7th (HST2STHA) and 13th (HST3MTHA) visit. During each HST participants cycled at 40% V̇O2max for 45 min in the heat (40 °C, 50% relative humidity (rh)). Participants completed 5 consecutive days of a 60 min active ISOCON HA protocol (40 °C, 50% rh; target Tre 38.5 °C) between HST1 and HST2STHA and 5 more between HST2STHA and HST3MTHA. Heart rate (HR), rectal temperature (Tre), perceived exertion (RPE) and thermal perceptions (TS, TC) were recorded at rest and every 5 min during exercise, whereas expired air samples for gas exchange analysis were obtained at 15, 30 and 45 min.

Results STHA and MTHA lowered resting (STHA: -0.38 ± 0.26 °C; MTHA: -0.40 ± 0.26 °C) mean (STHA: -0.36 ± 0.26 °C; MTHA: -0.52 ± 0.26 °C), and peak (STHA: -0.39 ± 0.64°C; MTHA: -0.59 ± 0.38 °C) Tre (P<0.05). Resting (P=0.84), mean (P=0.07), and final (P=0.16) Tre were similar in HST2STHA and HST3MTHA. Mean resting HR was similar in HST1 compared to HST2STHA (P=0.08) but was higher than HST3MTHA (P=0.04). HR increased throughout all trials, with an overall mean HR higher in HST1, compared to HST2STHA and HST3MTHA. In all HSTs, perceptual measurements increased with the highest perceptual strain seen in HST1 compared to HST3MTHA (P<0.001). Reductions in V̇O2, V̇CO2 and RER were noted when comparing HST3 to HST1, (Table 1.).

Conclusion An active, ISOCON STHA and MTHA protocol was successful at reducing the thermoregulatory, cardiovascular, and perceptual strain experienced when exercising in the heat.

10-day Heat Acclimation Using a Water-perfused Garment Post-exercise

ABSTRACT. Introduction: Little research investigated benefits of further elevating core temperatures using a heating garment after exercise for HA. This study aimed to explore changes in physiological and perceptual responses after a 10-day HA program with a water-perfused skin heating suit after exercise. Method: Twelve males were randomly assigned to either the control HA (HAEXE; N=6) or post-exercise HA (HAEXE+SUIT; N=6) group. Before (PRE) and after (POST) participating in the HA program, subjects were exposed to a Tair of 33oC and 60%RH immersing legs in 42oC water for 1-hour as a heat tolerance test. The HA program involved 10 consecutive days of 2-hour exposure to a Tair of 33oC and 60%RH. HAEXE finished 1-hour treadmill exercise (6km/h) followed by a 1-hour seated rest. HAEXE+SUIT conducted the same 1-hour exercise and then were dressed in the developed water-perfused suit which heated the chest, abdomen, upper and lower back, thigh with 44.2oC water, to complete 1-hour post-exercise HA program. Results: During the 10 days, increases in Tre during exercise were 1.06±0.19oC and 0.97±0.17oC for HAEXE and HAEXE+SUIT respectively, with no significant difference. 1-hour additional skin heating using the water-perfused suit further increased Tre by 0.54±0.15oC in HAEXE+SUIT whereas Tre decreased by 0.40±0.12oC in HAEXE during rest (P<0.001). HR for HAEXE+SUIT significantly decreased in POST (PRE: 90±4 bpm; POST: 82±4 bpm) (P<0.01). Body mass loss (PRE: 3.25±0.62 g/h/kg; POST: 4.12±0.82 g/h/kg, P<0.01), chest (PRE: 0.09±0.08 g/h/cm2; POST: 0.17±0.11 g/h/cm2, P<0.01) and forearm local sweat rates at the end of the immersion (PRE: 0.42±0.13 mg/cm2/min; POST: 0.62±0.20 mg/cm2/min, P<0.05) significantly increased in POST only for HAEXE+SUIT. In both groups, systolic blood pressures dropped, subjective responses were improved and no significant differences in Tre were found. Conclusion: Post-exercise skin heating using the water-perfused suit better induced HA than when only the active HA strategy was applied.

Thermal cardiac reactivity and Q10 effect related to heat acclimation

ABSTRACT. Introduction: Heat acclimation (HA) is an essential modifier of the physiological strain when working in the heat. It is unknown whether HA influences the increase of energy expenditure (Q10 effect) or heart rate (thermal cardiac reactivity TCR) due to increased body temperature. Method: We studied these questions using a heat stress database of climate chamber experiments performed by 5 young males in either non-acclimated or acclimated state. Measured oxygen consumption rates (VO2), heart rates (HR) and rectal temperatures (Tre) averaged over the third hour of each exposure were obtained from overall 273 trials organized in 10 series (5 persons × 2 states of acclimation). While workload (walking at the level, 4 km/h) and clothing (predominantly Icl 0.1) were kept for all series, heat stress conditions varied widely (ta 25-55 °C, pa 0.5-5.3 kPa, va 0.3-2 m/s, tr=ta). HA was induced by repeated experiments over a minimum of three weeks in a way that the subjects could sustain three hours of heat exposure reaching a Tre of 38.5 °C. Non-acclimated exposures were done in wintertime with a maximum of two exposures per week. The influence of Tre and HA on VO2 and HR was analyzed separately with mixed model ANCOVA. Results: Rising Tre increased significantly (p<0.01) both VO2 (by about 7 % per degree increase of Tre) and HR (by 38-40 bpm per degree Tre); neither slope nor intercept depended significantly on HA (p>0.1). Conclusions: The effects of Tre in this study agree with former outcomes for VO2 (an increase of 7 % corresponds to a Q10 factor around 2) and for HR (TCR of 33 bpm/°C in ISO 9886). Our results indicate that both relations are independent of HA; this may be important when assessing physiological strain at workplaces (e.g. ISO 8996 or ISO 9886) and for modelling heat balance.

13:00-14:30 Session 8: Impact of cold exposure on individuals with clinical disease
Impact of Cold Exposure on Individuals with Clinical Disease: Cardiovascular diseases, cold exposure and exercise

ABSTRACT. Both acute and prolonged cold exposure affect cardiovascular responses, which may be modified by an underlying cardiovascular disease. These can lead to a higher amount of cardiac symptoms, as well as adverse events during the cold season. Exercise in a cold environment increases cardiovascular strain further, and potentially also health risks, but its effects among persons with cardiovascular diseases are not well known. Controlled studies employing whole-body or local cold exposure demonstrate comparable or augmented increase in cardiac workload, but aggravated cutaneous vasoconstriction in persons with mild hypertension (HTN). So far, it is not known how exercise modifies cardiovascular responses among persons with HTN. Cold exposure reduces myocardial oxygen supply in coronary artery disease (CAD), possibly leading to ischemia. Simultaneously, exercise in cold augment cardiac workload in persons with CAD more than in a neutral environment. This can lead to earlier ischemia, angina and impaired performance. Also having a heart failure (HF) impairs submaximal and maximal performance in the cold. Antianginal medication is beneficial in the cold for lowering blood pressure, but does not affect the magnitude of cold-related cardiovascular responses in HTN. Cardioprotective medication also reduces the risk for ischemic sudden deaths due to cold. Similarly, the use of blood pressure lowering drugs improves exercise performance in cold both among persons with CAD and HF. Finally, also protection of the head region lowers blood pressure increase in cold. Both the acute and seasonal effects of cold and added with exercise may contribute to the higher morbidity and mortality of those with cardiovascular diseases. Yet, more studies are warranted for understanding the pathophysiological mechanisms underlying the adverse cold-related health effects.

Impact of Cold Exposure on Individuals with Clinical Disease. Respiratory responses to cold exposure

ABSTRACT. Cold dry air can have several effects on the respiratory system, especially in individuals with chronic lung diseases. Asthma is a chronic inflammatory airway disease characterized by repeated episodes of wheezing, coughing and breathlessness, and the global prevalence of doctor-diagnosed asthma in adults has been reported to be 4.3%, with wide differences between countries1. Exercise-induced asthma (EIA) is present in up to 90% of all individuals with asthma, and the cold, dry air during the winter months is particularly conducive to the development of EIA in susceptible individuals.

Asthma rates vary widely among sports, and both the type of exercise and the environment influence the severity of EIA in the individual asthmatic athlete. The main determinants of the bronchoconstrictor response to exercise are intensity (minute ventilation), the temperature and humidity of the inspired air, and baseline airway reactivity. Invasive studies have found pathological changes in airway mucosa that suggest airway remodelling, indicating that hyperventilation of cold, dry air represents a significant stress to the airways that could lead to asthma. Occupational studies indicate that prolonged exposure to cold air may induce a chronic asthma-like condition, even in healthy subjects.

EIA should be treated in athletes according to the same principles as in ordinary asthma patients. Competitive athletes must also consider doping control issues, since not all antiasthmatic medications are approved by the World Anti-doping Agency. The severity of EIA can also be reduced by raising the temperature and humidity of the inspired air, and heat-exchanging masks and devices have been developed for this purpose.

Impact of Cold Exposure on Individuals with Clinical Disease Impact of cold acclimation on glucose- and lipid metabolism in type 2 diabetes mellitus

ABSTRACT. Michiel P.B. Moonen

Dept. of Nutrition and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, the Netherlands

The number of people with type 2 diabetes mellitus (T2DM) is increasing worldwide. This metabolic disorder is characterised by reduced insulin sensitivity, leading to a negatively affected glucose and lipid metabolism. Because of this deranged metabolism, patients with T2DM have an increased risk of developing cardiovascular disease. Prolonged cold exposure with correspondingly increased energy expenditure could be used to improve insulin sensitivity and the disrupted metabolism in T2DM.

Mild cold exposure, both acute and prolonged, can increase non-shivering thermogenesis via activation of brown adipose tissue (BAT) and skeletal muscle (SM). The activation of these tissues increases insulin sensitivity, for instance by changing glucose transport characteristics of skeletal muscle (Glucose transporter (Glut4) translocation). Cold exposure can also improve lipid metabolism, via an increased uptake and combustion of lipids such as fatty acids and triglycerides. These combined effects of regular cold exposure therefore decrease insulin resistance and reduce the risk of cardiovascular diseases in patients with T2DM.

With the use indirect calorimetrics, hyperinsulinemic euglycemic clamp techniques and high-fat meal tests, we aim to further unravel these effects of cold exposure in human metabolism. Currently we are focusing on the effects of acute mild cold exposure on lipid metabolism and the role of BAT and SM activation in clearing lipids from the blood stream.

14:30-15:00 Session 9: Posters Tuesday
Location: Marble hall
Thermal and cardiovascular strain in middle-aged adults with and without type 2 diabetes during a brief exposure to hot-dry heat

ABSTRACT. Introduction. Aging exacerbates hyperthermia and cardiovascular strain during exposure to extreme heat, but it remains unclear whether those effects worsen in older adults with type 2 diabetes (T2D). Methods. We examined whole-body heat exchange in habitually active, middle-aged (mean±SD; age: 60±7 years) adults (10 males and 2 females per group) with (n=12, HbA1c: 7.0±1.0%, duration of T2D: 11±5 years) and without T2D (Control, n=12) matched for age, sex, and physical characteristics while resting in extreme heat (44°C, 30% relative humidity) for a brief 3-hour exposure. Metabolic heat production, whole-body net heat loss (dry±evaporative heat loss), body heat storage (temporal summation of heat production and net heat loss), and rectal temperature were measured continuously. Cardiovascular responses (heart rate, cardiac output, mean arterial pressure, and forearm and calf blood flow) were measured before and after the 3-hour exposure. Results: No between-group differences for metabolic heat production (T2D vs. Control; 111±17 vs. 113±18 W), evaporative heat loss (170±29 vs. 173±32 W), dry heat exchange (-99±28 vs. -98±21 W), and net heat loss (71±22 vs. 75±25 W) were observed over the 3-hours (all p>0.05). Consequently, the change in body heat storage (T2D: 344±111 kJ; Control: 346±139 kJ) and core temperature (T2D: 0.4±0.2°C; Control: 0.5±0.3°C) was similar between groups over the 3-hours (both P>0.05). Furthermore, no between-group differences in heart rate (T2D vs. Control; +19±9 vs. +15±7 beats.min-1), cardiac output (+0.2±0.6 vs. -0.4±0.7 L·min-1), mean arterial pressure (+0±6 vs. +2±7 mmHg), and forearm (+1.5±1.9 vs. +2.2±1.5 ml·100 ml tissue−1·min−1) and calf blood flow (+1.3±0.8 vs. +1.4±1.2 ml·100 ml tissue−1·min−1) were observed when expressed as a change from baseline (all P>0.05). Conclusions: Habitually active middle-aged adults with well-controlled T2D do not experience greater hyperthermia and cardiovascular strain compared to their healthy counterparts during a brief 3-hour exposure to hot-dry heat. Funding: Canadian Institutes of Health Research.

How Much Heat Can a Thermal Manikin Handle?

ABSTRACT. Introduction: Thermal manikin research is well established for cool and cold environments, and also for heat exposure within compensable conditions where the manikin does not overheat. High intensity heat exposure and potential skin burn injury is typically characterized using flame manikins exposed to short-duration flash fire conditions. There exists a large range of human exposure conditions between these two ranges which can be challenging to characterize with existing manikin technology.

Method: A prototype thermal manikin segment based on the Thermetrics ANDI water-cooled manikin technology was constructed and exposed to a range of radiant heat conditions (0.5 to 3.5 kW/m2) using a variable output radiant lamp array. The incident heat flux was recorded using a thin film heat flux transducer (Vatell Co.) at each interval. Surface temperature was reported for the manikin segments after reaching quasi-steady-state at 2 minutes exposure duration. Benchmark data to represent typical human skin temperature was generated using the three layer skin model described in ASTM F1930-13 also computed over a 2 minute exposure interval.

Results: The quasi-steady state temperatures for the manikin segment and the benchmark simulation are illustrated in the figure below.

Conclusions: When exposed to a radiant heat load of comparable magnitude, the quasi-steady state temperature of the water cooled manikin segment is comparable to a simulated human skin response. At lower heat fluxes, the manikin under-predicts the skin temperature which can easily be corrected with addition of heat from the manikin heaters. At the higher heat fluxes, the manikin over-predicts versus the simulation, potentially indicating upper limits of operation. Further evaluation and optimization of the manikin segment design may yield additional heat removal capability at higher heat flux levels.

The impact of a controlled hyperthermia heat acclimation program on aerobic exercise capacity
PRESENTER: Puck Alkemade

ABSTRACT. Introduction: The effect of heat acclimation (HA) on aerobic exercise capacity is subject to debate. Therefore, the aim of this study was to investigate the impact of controlled hyperthermia HA on aerobic exercise capacity.

Method: Twenty-three recreationally active to well-trained participants (14 males, 9 females; VO2max range 36.2 – 68.6 mL/kg/min) performed a graded exercise test (GXT) in thermoneutral conditions (~22°C, ~35% relative humidity), four to eight days pre and post HA. Cycling started at 25 W and power output was increased with 25 W/min until exhaustion. HA included two heat stress tests (HSTs) and 10 days of controlled hyperthermia HA sessions (33°C, 65% relative humidity). HSTs were performed one day prior to and two days after HA and involved 35 min cycling at 1.5 W/kg bodyweight, followed by an incremental time to exhaustion test (25 W/min).

Results: VO2max was not altered following HA (+0.7 [-1.2 2.5] ml/kg/min, p = 0.46). A negative association was observed between initial VO2max and the change in VO2max from pre- to post HA (ΔVO2max,post-pre; rs = -0.5, p = 0.02). Time to exhaustion (TTE) for both GXTs could only be derived for a subset of participants (n = 14; 8 males, 6 females; VO2max range 38.7 – 68.6 mL/kg/min). For this subset, TTE was improved following HA (+2.7 [0.4 4.9] % ; p = 0.02), while VO2max was not (+0.1 [-2.2 2.4] mL/kg/min, p = 0.92).

Conclusion: HA using controlled hyperthermia did not improve maximal oxygen uptake. However, less fit individuals – indicated by a lower initial VO2max – exhibited a larger improvement in VO2max compared to those who were more fit. TTE for the GXT was increased following HA. It should be noted that further analysis is required to confirm these findings.

The effect of heat acclimation on cognitive performance

ABSTRACT. Introduction: The increasing frequency of summer heat waves as a consequence of climate change presents a significant detrimental impact on human health. In occupational settings, this is reflected in the drop in productivity. While not affecting routine work performance, prolonged heat exposure might impact cognitive performance and extend task duration. Several studies indicate that heat acclimation improves physical performance. Whether this is reflected in mental performance was investigated in the present study. Methods: Eight male participants underwent a 10-day normobaric hypoxic confinement (13.5% FiO2) with daily 90-min normoxic controlled-hyperthermia (ambient temperature: 37.4±0.5°C, target rectal temperature: 38.5°C) heat acclimation protocol. On days 1 and 10, the participants were passively heated for an additional 2-hr after the training sessions. Before and after these training sessions (pre- and post- training, respectively) and after 2-hr of passive heat exposure they completed a Trail Making Test (TMT), connecting letters with suitable numbers on tablets. The number of errors, total duration and calculated fatigue were recorded. Results: Compared to pre-training, participants demonstrated greater fatigue after completing the 90-min training session post-training, which was not evident after 2-hr of additional heat exposure in both testing days. Heat acclimation improved participants` pre- and post-training reaction time by 11-sec and 8-sec, respectively. Additional 2-hr of passive heat exposure did not indicate heat acclimation improvements in TMT results. Heat acclimation did not facilitate cognitive performance assessed after participants were exposed to the 2-hr passive heat. Conclusions: Heat acclimation incorporating exercise significantly improved reaction time and time to complete cognitive tasks.

This study was supported by the Slovene Research Agency (project no. Z7-9412) and by the European Commission Horizon 2020 Programme (“Heat-Shield” project; contract number: 668786)

Estimation of Core Temperature from Near-infrared Imaging of Hand Vein Dynamics

ABSTRACT. Introduction: The blood vessel diameter responds dynamically depending on the thermal condition of the body, tending to constrict when exposed to cold stress and to expand during heat stress. This study has developed as a method for inferring core temperature (CT) from NIR images of hand dorsal vein patterns.

Method: Experiments were run to distinguish how CT and local temperature (LT) affect hand dorsal vein diameter. Healthy volunteer subjects participated in the experiment. The protocol began with measuring the room temperature (24°C) and the dorsal skin temperature of the hand. One hand was imaged at room temperature and another was imaged after heating by an infrared lamp to increase the temperature on the dorsal part of the hand to 37–40°C. Medium-intensity exercise (about 15-min treadmill) is performed in high room temperature (29-30°C) for increasing the core temperature by 1–1.5°C. In our experiment, we have considered the tympanic temperature as a core temperature reference. 940 nm as NIR light source is used for imaging and vein diameter was measured automatically using ImageJ software.

Results: After the experiment, the maximum diameter of the blood vessel (DBV) relative to the baseline (%DBV) was calculated as the maximum value divided by the baseline value [%DBV = (maximum DBV)/(baseline DBV) × 100]. The rate of vasodilation (%VD) as a percent change relative to the baseline, was also calculated using the following equation: %VD = %DBV - 100. The percent of core temperature change (ΔCT) and percent of vessel diameter change (ΔVD) has a non-linear relation which we found by training a regression model from the experimental data. We also computed the RMSE for these regression models. The regression models of ΔCT and ΔVD has R2 = 0.897 and RMSE of 0.7428.

Conclusions: During thermoregulatory processes in the veins, blood volume changes and it causes vein dilation that can indicate heat stress. Core body temperature can be estimated from these changes in vein diameter using a trained regression model.

The effects of short- and medium-term heat acclimation on the sensations of fatigue

ABSTRACT. Introduction: The physiological adaptations following heat acclimation (HA) are well documented, although, data considering an individual’s sensation of fatigue following repeated exercise-heat stress are less well understood. Previously, ultra-endurance runners report lessened percieved fatigue following short-term HA (STHA) (Willmott et al., 2017). However, if STHA is extended and/or includes more than one exposure per day, as found during fire instructors’ shift patterns (Watt et al., 2016), there is a risk of increased sensations of fatigue, which may be detrimental, and negate the efficacy and applicability of HA. Therefore, the aim of this study was to describe the sensations of fatigue following short- (STHA: 5 session) and medium-term heat acclimation (MTHA: 10 sessions) during once-daily HA (ODHA) and twice-daily HA (TDHA).

Method: Twenty male participants (mass: 77.9 ± 11.9kg, peak oxygen uptake [V̇O2peak]: 3.75 ± 0.47L.min-1) completed a V̇O2peak test before and after 10-sessions (60-mins cycling at of ODHA (n=10) or non-consecutive TDHA (n=10) (45°C, 20% R.H.). Sensations of fatigue (General, Physical, Emotional, Mental, Vigour and Total Fatigue) were assesed using the multi-dimensional fatigue scale inventory-short form (Stein et al., 2004) pre and post session 1, 5 and 10.

Results: HA adaptation (reductions in resting rectal temperature and heart rate, plasma volume expansion and increased sweat rate) was induced following ODHA and TDHA (P<0.05) (Willmott et al., 2018). General, Physical and Total Fatigue increased from pre to post session 1 within both groups (P<0.05). However, pre to post session changes for General, Physical and Total Fatigue were lower (P<0.05) in session 5 and 10 of ODHA, but were only lower after session 10 of TDHA.

Conclusions: Whilst comparative heat adaptations followed non-consecutive TDHA, the increased sensation of fatigue following HA only reduced by session 10 (MTHA), whereas this response occured by session 5 (STHA) of ODHA.

On the development of a hybrid of Fiala’s and Wissler’s shivering models: A preliminary investigation
PRESENTER: Allen Curran

ABSTRACT. Introduction: One application of human thermo-physiology models (HTMs) is to predict time-to-comfort for occupants of vehicles that have been subjected to a cold-soak and then heated. We have used both Fiala’s (2001) and Wissler’s (2018) shivering models integrated into an HTM. Our experience has been that Fiala’s model tends to over-predict shivering metabolism while Wissler’s model tends to under-predict.

We compared HTM predictions to cold air test (SCAT) data published by Launay (2006). Fiala’s model over-predicted shivering metabolism and skin temperature (at the end of the SCAT) by 30 percent and 2.4 °C, respectively. Wissler’s model under-predicted by 10 percent and 0.7 °C. Despite the seemingly better predictions from Wissler’s model, we cannot use it for human comfort studies since it lacks a dynamic term, i.e., one that incorporates the derivative of skin temperature, which is essential for comfort evaluation at the beginning of a cold-soak test.

Method: Fiala’s model uses a sigmoid function to predict the contribution of the skin temperature error signal to metabolic shivering. Wissler’s model uses an “effective temperature” that provides similar functionality. We developed a “hybrid” model by modifying Fiala’s shivering equation to use the proportionality constants for the core and skin afferent signals from Wissler’s model.

Results: When compared to Launay’s measurements, the hybrid model under-predicts shivering metabolism and skin temperature by 6 percent and 0.1 °C. However, the transient portion of the prediction is still inaccurate.

Conclusions: The results of the SCAT investigation matched our experience that Fiala’s model tends to over-predict shivering metabolism while Wissler’s model tends to under-predict. To avoid lengthy regression analyses, we created a modified version of Fiala’s model to match the predictions from Wissler’s model while still maintaining a dynamic term. The hybrid model yielded better results for this data set than either of the original models.

Age differences in cardiac autonomic modulation during intermittent exercise in the heat

ABSTRACT. Introduction: Heat exposure is associated with higher morbidity and mortality among older individuals. This can in part be attributed to age-related impairments in heat dissipation. While the mechanisms underlying this maladaptive remains unclear, age-related differences in cardiac autonomic function may play an important role. Thus, this study aimed to detect potential differences in heart rate variability (HRV) during a moderate-intensity intermittent exercise in the heat among young (25.8±1.9 years), middle-aged (43.5±2.8 years), and older (62.9±3.7 years) men Method: Thirty-three participants (11 per group) performed four successive bouts of 15-min cycling at a moderate fixed rate of metabolic heat production at ~400 W; each separated by a 15-min recovery with 1 hour of final recovery in a hot and dry environment (35°C, 20% relative humidity). Twelve HRV indices (e.g. low and high frequency power, Shannon Entropy, and others) characterizing common domains of variability and complexity of heart rate were computed and assessed at baseline resting, end of each successive exercise and recovery cycle and final 1-hour recovery. Results: Cardiac autonomic modulation during intermittent exercise in the heat, as well as during resting and recovery was significantly affected by age, as changes were observed among the three different aged groups in five indices (p≤0.05). Similarly, time influenced cardiac autonomic modulation as three indices showed changes across time (p≤0.05) during intermittent exercise whilst four indices displayed significant changes (p≤0.05) during rest and recovery in the heat. Conclusions: We show that intermittent exercise in the heat is associated with cardiac autonomic dysregulation in older men, as compared to young and middle-aged men even when a brief 15-min break is intersperse between exercise bouts. Protective measures must be developed to safeguard older adults against heat-related illness during exercise in hot environments.

The effect of respiratory muscle activation on the blood volume in locomotor muscle during incremental ramp cycling

ABSTRACT. Introduction: Respiratory muscle activation during severe exercise may prevent the blood flow increase for locomotor muscles and then it is a putative factor to limit several works under various environments. However, it is still unclear whether locomotor muscle blood volume as a factor changing blood flow is influenced by activated respiratory muscle during severe exercise. We investigated the deoxygenated [Hb+Mb] (HHb, index of fractional O2 extraction) and total [Hb+Mb] (THb, index of total blood volume) in respiratory (intercostal muscle and diaphragm, IC-DP) and locomotor muscle (vastus lateralis, VL) using near-infrared time-resolved spectroscopy. Method: Ten males performed ramp incremental cycling (20 W.min-1) to exhaustion with measuring pulmonary VO2 and absolute concentrations of HHb and THb at the left 9-10th intercostal place and VL muscle. Results: The HHb values were greater for VL than IC-DP from 55 to 100 % of normalized power output (PON) (95.7 ± 35.7 vs. 65.6 ± 10.7 µM at 100 % PON, P < 0.05) with the plateau response following linear increase in VL and the steep increase after plateau in IC-DP. The THb values were greater in VL than IC-DP from 30 to 100 % PON (200.7 ± 18.1 vs. 162.6 ± 11.6 µM at 100 % PON, P < 0.05) with the plateau response following linear increase in VL and the linear reduction in IC-DP. Onset of steep HHb increase in IC-DP was slower than that of plateau THb in VL (76.9 ± 6.1 vs. 59.0 ± 10.5 % PON, P < 0.05) without a significant correlation (r = -0.32). Conclusions: These suggest that respiratory muscle activation investigated in the present study may not inhibit blood flow regulation associated with local blood volume in locomotor muscles.

Heat acclimation does not alter heart rate variability at rest in normobaric hypoxia.

ABSTRACT. Introduction: Cross acclimation is the process of inducing physiological adaptation utilising one environmental stressor (e.g. heat) with resultant beneficial physiological response in another (e.g. hypoxia). To this end, heat acclimation (HA) improves physiological responses at rest, as well as during submaximal and maximal exercise in hypoxia. Heart rate variability (HRV) describes autonomic activity and improvements in HRV have been evidenced during heat stress following HA, and in hypoxia following cold adaptation. The aim of this study was to examine whether heat-hypoxic cross acclimation altered HRV. It was hypothesised that HA would improve indices of HRV at rest in hypoxia.

Method: Sixteen healthy male participants completed ten 90-min sessions of isothermic HA (40°C/40% relative humidity [R.H.]) or exercise training ([CON]; 20°C/40% R.H.). A 10-min normobaric hypoxic exposure (FiO2 = 0.12; ~4,300 m) was undertaken 24 hours prior too, and 24 hours following HA or CON. During this trial a 3-lead ECG was performed, and ventilation was measured via a metabolic cart in the supine position. Time (R-R interval and standard deviation of R-R intervals [SDNN]) and frequency (total power, low frequency power [LF; range 0.04–0.15 Hz], high frequency power [HF; range 0.15–0.4 Hz] and low:high frequency ratio [LF:HF]) domain parameters were calculated using Kubios HRV analysis software on the final 5 min of ECG sampling. HRV data was analysed using mixed 2-way ANOVA on absolute values.

Results: HA, but not CON, reduced resting rectal temperatures and HR, and increased sweat rate and plasma volume in normoxia (p<0.05). No changes over time, or between groups were observed in breathing frequency, R-R interval, R-R SDNN, total power, LF, HF or LF:HF in hypoxia (p>0.05).

Conclusions: HRV did not change in hypoxia following HA, suggesting autonomic activity at rest is not altered as part of heat-hypoxic cross acclimation.

Study on assessing suitable working duration wearing infection protective clothing for medical workers
PRESENTER: Ayano Dempoya

ABSTRACT. Introduction: Medical workers who perform medical procedures wearing protective clothing to prevent infection are required not only to carry out highly active tasks such as transferring patients, but also to perform accurate work. Protective clothing worn at the time of nosocomial infection is highly sealed and makes medical workers feel hot thermal sensation. The medical workers are not satisfied with the comfort and mobility of the protective clothing. The present study examined thermal comfort in working duration wearing protective clothing. Method: Ten healthy men wore low- or high-moisture permeability protective clothing respectively (TY or AZ) and performed 20 minutes of step exercise (3 Mets) and took a sitting position for 20 minutes before and after the exercise at 23℃, 50%RH. Body weight loss, sweat absorbed by clothing, subjective vote, heart rate, and oral temperature were measured. Also, we conducted an experiment on the stair climbing exercise (6 Mets) in the same environment. Results: Although there was no difference in the oral temperature between protective clothing in any of the exercises, thermal sensation of TY was hotter than AZ, and the subjective wettedness and discomfort of TY were larger. In the step exercise, TY induced more weight loss than AZ, and sweat absorbed by clothing of TY was increased significantly (P <0.01) compared with AZ. Two subjects were unable to continue the experiments 10 minutes after the start of the stair climbing exercise when wearing TY. Conclusions: Although the medical practice for patients with infections usually takes about 2 hours, it is suggested that the current protective clothing has a limit on wearing time because of the thermal sensation, which may restrict the medical practice. Protective clothing for infection control for medical workers needs some improvement. This study was supported in part by Grants-in-Aid for Scientific Research (JP215H02581) from JSPS.

Does Heat Thermotherapy Improve Cardiovascular and Cardiometabolic Health? A Systematic Review and Narrative Synthesis of the Literature

ABSTRACT. Introduction: A systematic review and synthesis of the literature were conducted to assess whether heat thermotherapy improves cardiovascular and cardiometabolic health, whilst comparing different heat thermotherapy modalities.

Method: Three major electronic databases (Medline, Embase and Web of Science) were searched from the earliest available date until 24th November 2018 and a manual literature search, using the key terms of ‘induced hyperthermia’, ‘trial’ and ‘adults’ was conducted. Inclusion criteria were articles with a control trial study design and a passive heating intervention. In total 1036 articles were identified and screened, with 31 articles meeting the inclusion criteria. A narrative synthesis was undertaken in four stages, including the development of a theory, developing a preliminary synthesis, exploring relationships and assessing the robustness of the synthesis.

Results: In the 31 included articles, thermotherapy was delivered acutely (one bout; n=13), short term (2-15 bouts; n=12) and chronically (>15 bouts; n=6). The stimulus was hot water immersion (n=22; water temperature 38-43°C), heated air exposure (n=7; air temperature 31-90°C) and a water-perfused suit (n=2). The heat exposure duration was from 10 to 240 minutes.

Cardiovascular and cardiometabolic measurement techniques varied across articles, alongside participant age (≤35 years, n=365; >35 ≤60 years, n=166 and >60 years, n=366) and health status. 17/23 articles measuring cardiovascular outcomes reported positive cardiovascular health benefits, including increased flow-mediated dilation (1.3-5.3%) and systolic blood pressure (4-16mmHg). 10/14 articles measuring cardiometabolic outcomes reported positive cardiometabolic health benefits, including reductions in postprandial glucose concentration and C-reactive protein. Only two papers investigated the decay effect of thermotherapy.

Conclusion: Overall, 23/31 papers demonstrated significant positive cardiovascular or cardiometabolic health benefits by thermotherapy, despite varied study design and modality. This review has quantified the different thermotherapy interventions and concluded thermotherapy does result in cardiometabolic and cardiovascular health benefits. However, the duration of these health benefits post-thermotherapy is unknown.

Active local cooling for the prevention of onycholysis during docetaxel-based chemotherapy

ABSTRACT. Chemotherapy-induced onycholysis is a severe form of nail toxicity and is characterized by partial or complete detachment of the nail from the nail bed. Ice gloves can be effective in preventing nail toxicity as they enable cold-induced vasoconstriction, or reduction of blood flow, and therefore limit the transport of chemotherapeutic agents towards the nail bed. After several minutes, the ice gloves induce cold-induced vasodilation, which reduces the effectiveness of the preventive treatment. Moreover, the gloves cause pain and additional distress during chemotherapy. The objective of this article is to examine the usefulness of an innovative active local cooling device for the prevention of onycholysis during docetaxel-based chemotherapy, while limiting pain and discomfort.

In this research, a prototype of an active cooling device was developed that allows the cooling of the palmar side of the distal phalanges with an alternating temperature of 2°C to 20°C every three minutes. Six cancer patients – five men and one woman – undergoing a docetaxel-based treatment participated in this study. The hands of the patients were photographed and discoloration was evaluated by quantifying average RGB-values over time of every fingernail.

The results indicate that the patients experienced the ice glove as significantly less comfortable, which led to reduced therapy-loyalty towards the ice glove. Furthermore, two of the six patients experienced frostbite – at one and respectively two fingers – caused by the ice glove, which resulted in discoloration of the fingernails. Nevertheless, no symptoms of onycholysis were observed on both hands.

In conclusion, the results of this study show that the active local cooling device can be useful for preventing nail toxicity, while offering a relatively painless treatment compared to the ice glove. Further research is necessary to investigate and compare additional cooling strategies where patient comfort and usefulness of the device are in balance.

Eccrine sweat glands ion reabsorption in healthy older adult after heat acclimation
PRESENTER: Nicola Gerrett

ABSTRACT. Introduction: The adaptation of older adults’ eccrine sweat glands to a controlled hyperthermic (CH) heat acclimation protocol is not well known. However, CH is a challenging protocol, therefore we investigated these adaptations in healthy older adults to a modified CH protocol. Method: 10 healthy older adults (>65 yrs) completed 9 non-consecutive days via cycling in 35˚C, 45% RH with 1.0˚C increased rectal temperature for a controlled hyperthermia. The sweat glands maximum ion reabsorption rate, sweat rate, sweat sodium chloride concentration, number of activated sweat gland were used as markers of sweat gland adaptation These were assessed via a passive heating protocol (lower leg 42˚C water submersion) pre and post heat acclimation (HA). Results: Some markers of thermoregulatory adaptations were evident after HA; lower resting rectal temperature, plasma volume expansion, reduced thermal sensation (p<0.05) but no changes in heart rate (p>0.05). Ion reabsorption was enhanced at the chest (p<0.05) but not at the forearm or thigh (p>0.05). Gross sweat loss and local sweat rate increased, whilst sweat sodium chloride concentration decreased (p<0.05). The number of heat-activated sweat glands did not increase post HA nor in response to an iontophoresis stimulus (p>0.05). The Tre threshold for the onset of sweating improved for some but not all participants. Conclusions: Healthy older adults are able to acclimate to an adapted (i.e. easier) CH protocol as evident but the changes in the key thermophysiological markers of acclimation. Improvements in the maximum ion reabsorption rates were observed more clearly at the chest compared to the forearm or thigh. Sweat gland function showed modest improvements after HA. Sweat production is usually higher on the torso and the decline with age is attenuated compared to the extremities, which may explain the improvements observed at the chest only. Further analysis is required to confirm these findings.

Caretaker assessment of thermal state of children in day-care centers

ABSTRACT. Introduction: Young children are vulnerable to extreme temperatures due to physiological and anatomical characteristics and behavioral dependability, with the latter a relatively unexplored area. To quantify this, the current study investigated the effects of ambient temperature on the thermal state of children and caretakers in day-care centers, the ability of the caretakers to estimate the thermal state of the children and the knowledge of the caretakers on this topic. Method: From 6 different day-care centers in the Netherlands, 106 children (<4 years old) and 63 caretakers were recruited. Three times a day, during summer and winter, Wet Bulb Globe Temperature (WBGT) was measured out- and inside the day-care center. Skin temperature of the children and caretakers were measured. Thermal sensation and comfort of the caretakers about themselves and of the children were recorded and compared. Caretakers were interviewed about the precautionary temperature related measures that are taken in the day-care center and the knowledge regarding the effect of temperature on children. Results: Preliminary analysis with a multilevel mixed effect linear regression show a significant relation (p<.05) between the thermal sensation of the caretakers and their own skin temperature in summer and winter. However, no significant relation is found between the thermal sensation of the children estimated by the caretaker and the skin temperature of the children for summer (p=.126) and winter (p=.238) separately. Conclusions: Based on preliminary analysis it can be concluded that caretakers in day-care centers can correctly estimate their own thermal state, but have problems estimating the thermal state of the children correctly. However, additional analysis are required to confirm these findings.

Inter-individual variation in the adaptive response to heat acclimation; impact on temperate performance

ABSTRACT. Introduction: Typical heat acclimation (HA) responses are well characterised at the cohort level, however, individual data demonstrate considerable heterogeneity. Recent research suggests that HA indicies are independent and not influenced by aerobic capacity, previous HA or thermal dose. However, some baseline responses may be useful in estimating the potential benefits that an individual may obtain from HA. It remains to be establised whether the extent of individual HA will translate to aspects of individual endurance performance and thermophysiological indicies in temperate conditions, and if these can be related to any prior variables.

Method: 17 males (V̇O2max=58.8[8.4] mL∙kg-1∙min-1) undertook 10-days HA (exercise + heat-stress [40°C, 50% RH]). Adaptation was assessed by heat stress tests (HST; 60 minutes cycling, 35% peak power output), and performance was assessed by a graded exercise test and 30 minute work done trial (22°C, 50% RH), pre- and post-HA (within-participant repeated-measures design). The controlled hyperthermia (CH) protocol for HA was used (90 minutes 40°C, 50% RH, rectal temperature 38.5°C). Nine of the participants had previously undertaken a HA programme (3 to 18 months washout).

Results: At the group level HA was evident (hypervolemia, reduced rectal [Tre] and body temperature, reduced heart rate and increased sweating during HST; P<0.05). However there was notable inter-individual variation in the range of adaptive responses. These data have already established that aerobic capacity does not influence the degree of HA, however it has not yet been determined whether the magnitude of an individual’s HA response influences temperate endurance performance and associated changes in thermophysiological variables. Full data analysis is not yet complete and it is proposed that comparisons will be made to advance the evidence from Corbett at al. (2018) with considerations for previous HA and thermal dose.

Assessment and improvement of work environment in the sewing production situated in an older type of building

ABSTRACT. Introduction: According to previous studies sewing machine operators spend over 90% of their time indoors and over 30% of their time at work. Because the quality of indoor air is very important for the work environment. The target group of this study was completed of 130 workers from the garment industry in North-East Estonia. Method: To measure physical and chemical hazards in the present case study, international methods according to Estonian legislation were used. There were studied the chemical (like dust) and physical hazards (like temperature, relative humidity, CO2 etc) in a medium-sized sewing industry building where employees of small groups (7- 12 sewing machine operators) are located. The measured values were compared to the data of the large hall. The anonymous e-questionnaire was carried out. The rate of responses were over 35%. Results: Chemical hazards (dust and CO2) and physical hazards (microclimate, noise and lighting) were collected from various types of workplaces. Five different workspaces were investigated during the summer and winter period. Most of the respondents complained about the temperature being too hot in the workstation in summer and the air inflow being too scarce during winter. From the anonymous online questionnaires came out main problems with ventilation, temperature and dry skin, eyes and throat. Conclusions: From this study turns out that there are less problems with physical and chemical hazards in the old type industry building because there are small rooms separated by walls. It is easier to achieve the regulation of the mechanical ventilation and suitable microclimate in a small room, where smaller groups of workers are situated. They can use natural ventilation through opening windows. Chemical hazards like dust and carbon dioxide are lower. Illumination aspects like intensity and distribution are better achieved. Small work groups implement the correct ergonomic work postures.

Comparison of the Predicted Heat Strain and the Fiala-based Human Thermophysiological Model for normal and protective clothing under various ambient temperatures

ABSTRACT. The aim of this paper is to compare Predicted Heat Strain (PHS) based on the analytical approach and Fiala-based Human Thermophysiological model (FMTK) with the experimental data. For experiments, one male participant (80 kg, 1.75 m) and three types of ensembles were used: Klimatex underwear, protective clothing: FOP M2000, Tychem-F. The range of temperatures for neutral and hot conditions was from 25 °C to 40 °C and the activity during the tests was 1 met for resting and 3.2 – 4.3 met for exercise. The results showed that PHS index is possible to use for normal clothing under various ambient temperatures and can give results like FMTK model and experiment. For protective clothing, which has the value of clothing insulation higher than 1 clo (maximum value in the norm for using PHS index), it depends on the value of the static moisture permeability index imst. For its higher value (FOP M2000, imst =0.34), it is possible to use PHS index for prediction of the rectal temperature and mean skin temperature with sufficient accuracy. But for low values of imst, (Tychem-F, imst = 0.03), PHS index overpredicts the rectal temperature and give unrealistic results in comparison with the FMTK model and experiment.

A new device for continuously collecting sweat samples for measuring both sweat composition and volume

ABSTRACT. Introduction: Sweat is important for regulating body temperature in the heat and maintaining healthy skin. Sweat can be used as a non-invasive biomarker for assessing human performance, health and wellbeing. Recently, wearable biosensor devices are reported to measure sweat composition (Gao et al. 2013, Anastasova et al. 2016, Glennon et al. 2016). However, the sweat measured by these devices are contaminated due to the accumulation of sweat under the sensors which is not continuously removed. To solve these points, we developed a new device which flushes sweat continuously and allows for an accurate measurement of both sweat compositions and volume.

Method: A new device, consisting of a microfluidic chip, was attached onto the skin and two external micro-pumps to flush accumulating sweat in the fluidic channel (area: 2.72 cm2) at defined time intervals, was assessed. To fabricate the microfluidic chip, a disposable double-sided medical tape was cut with a laser ablation system and then the upper surface was covered with a silicone rubber sheet to provide the fluidic channel. To evaluate the device, we performed passive heating for 45 min with a water-perfused suite in a temperate environment (25°C, 50%Rh) with a healthy participant. During passive heating, we measured cardiovascular, thermoregulatory variables, sweat compositions and volume of the new device, sampling every 5 min.

Results: The new device could collect enough volume for measuring Na+, Cl- and K+ from forearm sweat at each 5 min intervals and these compositions at the end of passive heating were 56.6, 31.7 and 6.8 mmol/l, respectively. Sweat rate by the new device showed an almost 1.5 time higher rate than that of the ventilated capsule method.

Conclusions: Sweat composition measured by the new device were acceptable based on the earlier research. However, we need to improve the devices ability to measure sweat rate accurately.

Ice Vests Extend Physiological Work Time While Wearing Explosive Ordnance Disposal Protective Clothing in Hot Conditions
PRESENTER: Kate Hutchins

ABSTRACT. Introduction: Explosive ordnance disposal (EOD) technicians may be required to work in hot environments while wearing heavy protective clothing. The uncompensable heat stress experienced limits their work time in such conditions. We investigated the ability of an ice vest to attenuate physiological strain and subsequently extend work tolerance.

Method: Eight male participants (24.3±4.1 yr, 51.9±4.6 mL∙kg-1∙min-1) walked (4.5 km·h-1) on a treadmill in an environmental chamber (35 °C; 50 % relative humidity). Participants wore either an EOD suit (EOD; Med-Eng EOD 9; 33.4kg) or EOD and ice vest (EOD+IV;ICEEPAK Australia; 34.6kg). Heart rate, rectal and skin temperature were recorded continuously. Trials were terminated due to: rectal temperature 39 °C; 60 minutes walking duration; heart rate 90 % of maximum; volitional fatigue. Order of trials was randomised across participants, separated by at least seven days and commenced at the same time of the day.

Results: The majority of trials (15/16) were terminated based on heart rate criteria. Participants walked longer in EOD+IV compared to EOD (8.1±7.4 min, p<0.05). EOD+IV resulted in cooled skin and subsequently whole body temperatures (p<0.001). An interaction between condition and time was identified for heart rate, with EOD+IV becoming significantly lower after 30 minutes of exercise (p<0.001).

Conclusions: Work time improved by 21% in EOD+IV. The participant’s heart rate, skin and whole body temperature were lower while wearing the ice vest. With heat dissipation via the periphery facilitated by the EOD+IV, the observed reductions in heart rate may reflect the preservation of central blood volume enabling the heart to maintain cardiac output. Thus, the cardiovascular inefficiency that limited performance time in the EOD condition was attenuated. Overall, the results highlight the benefit of an inexpensive cooling device in assisting EOD technicians working in a hot environment.

Effects of ice slurry ingestion on occupational heat strain amongst indoor manual workers in Singapore

ABSTRACT. Introduction: Occupational heat stress (OHS) has been shown to be detrimental for workplace productivity and safety. OHS studies have largely been conducted in dry, outdoor environments in temperate countries. However, the level of OHS in humid, indoor environments in tropical countries has not been well studied. Therefore, we aimed to determine the level of OHS in an indoor manual labour setting in Singapore. We also sought to determine the efficacy of ice slurry ingestion in ameliorating the negative effects of heat strain in occupational settings.

Method: Six male manual labourers (mean±SD: age 26±4; BMI 25.6±2.8 kg/m2) working in an indoor warehouse (WBGT: 26.6±0.4℃; Tdb: 29.5±0.2℃, RH: 62±4%) participated in the study. Participants completed a familiarization trial and two experimental trials, where they consumed either ice slurry (ICE) or ambient drink (AMB) following ad libitum drinking schedule in a crossover counterbalanced manner.

Results: Mean Tc was elevated in both ICE and AMB trials. However, Tc was largely below 38℃, indicating low levels of thermal strain. Compared to AMB trial, participants in ICE trial had a lowered rate of rise of Tc (ICE: 0.093±0.063 ℃/h vs AMB: 0.151±0.087 ℃/h; p<0.05) and reduced estimated sweat rate (ICE: 0.213±0.096 L/h vs AMB: 0.299±0.046 L/h; p<0.05). However, RPE (p=0.925), thermal sensation (p=0.834), maximal back strength (p=0.580) and maximal arm strength (p=0.136) were similar between ICE and AMB trials. Tc, chest Tsk and HR profiles were similar between trials (p>0.05).

Conclusions: We observed low levels of thermal strain in an indoor manual labour setting in Singapore. As OHS is low, the efficacy of ice slurry ingestion could not be fully delineated. However, there is potential for ice slurry to be effective in reducing thermal strain and preventing dehydration. This effect may be enhanced when employed in occupational settings with higher levels of OHS.

A patient-centred evaluation of thermal resilience practices in temperature-sensitive people with Multiple Sclerosis

ABSTRACT. Introduction: Multiple sclerosis (MS) is a neurodegenerative disease characterized by temperature sensitivity, where changes in body temperature induce transient symptoms worsening. There is no pharmacological intervention for this condition and patients often develop their own thermal resilience practices. Yet, there is no formal evaluation of the variety and perceived effectiveness of those practices. The aim of the study was to survey the experience of temperature sensitivity and the individual strategies used to combat it, in MS.

Method: 458 people with MS (58.7% relapsing-remitting; 20.7% secondary-progressive; 14% primary-progressive; 6.6% unknown) completed an anonymous online survey. The questionnaire comprised sections aimed at characterizing participants’ general medical history; the symptoms worsening as a result of heat or cold, and thermal resilience techniques for heat and cold sensitivity.

Results: Overall, 53% of responders reported suffering from heat sensitivity, 15% from cold sensitivity, and 32% from both. Fatigue (79%), weakness (60%) and balance difficulties (56%) were prominent heat-induced symptoms. Muscle cramping (43%), fatigue (40%) and poor walking (36%) were prominent cold-induced symptoms. Participants reported exercise (91%) and long periods of inactivity (92%) as the greatest triggers of heat and cold sensitivity, respectively, that affects their MS symptoms. The most common thermal resilience practices in the heat were wearing lightweight, loose, breathable clothing (95%) and using fans (91%) (p<0.01), whereas wearing layers of clothes (93%) and staying in a heated environment (91%) (p<0.01) were commonly adopted to combat cold sensitivity.

Conclusions: Temperature sensitivity in MS worsens quality of life and disease management. The patient-centered information presented here will help to guide evidence-based interventions and investigations that are individually tailored to the specific experiences of temperature-sensitive people with MS.

Heat Related Issues and Practical Applications for Paralympic Athletes at Tokyo 2020
PRESENTER: Katy Griggs

ABSTRACT. International sporting competitions, including the Paralympic Games, are predominantly being held in hot and/or humid environmental conditions. Thus, a greater emphasis is being placed on preparing athletes for the potentially challenging environmental conditions of the host cities. Despite previous Olympic and Paralympic Games being held in Athens, Beijing and Rio, the impending Tokyo 2020 Games could be the most thermally demanding for both athletes and spectators alike. It is well recognised that exercising in hot and or/ humid ambient conditions increases physiological and psychological strain, causing an decline in sporting performance compared to competition in cooler conditions. However, for athletes that are eligible to compete in Paralympic sports, evidence-based practices for reducing thermal strain whilst competing in the heat are limited. This review aims to provide an overview of heat-related issues for Paralympic athletes at the greatest thermoregulatory risk, alongside current recommendations to reduce thermal strain and technological advancements in the lead up to the Tokyo 2020 Paralympic Games. When competing in challenging environmental conditions a number of factors may contribute to an athlete’s predisposition to heightened thermal strain. These include the characteristics of the sport itself (type, intensity, duration, modality, environmental conditions), fitness and physical attributes, but also the complexity and severity of the impairment of the athlete. For heat vulnerable Paralympic athletes, strategies such as the implementation of cooling methods and heat acclimation, can be used to combat the increase in heat strain. At an organisational level, regulations and specific heat policies should be considered for several Paralympic sports. Both the utilisation of individual strategies and specific heat health policies should ensure both the health of the athlete and maintenance of their sporting performance when competing in environmental conditions, such as those expected at the Tokyo 2020 Paralympic Games.

WATson - Development of a new device to determine the cooling function of textiles

ABSTRACT. Introduction: Textiles with new function are coming in the market and new test methods are necessary. Nowadays, cooling textiles are found in the field of sports and protective clothing. Cooling textiles should support the efficiency of athletes and workers. The cooling effect should improve comfort and wellbeing. During high activity and/or in warm environments the body core temperature can increase and human starts sweating to prevent an overheating of the body. The evaporation of liquid sweat is the most effective process to cool the body. Cooling textile should support the body to keep the body temperature constant. Method: To determine the cooling power of fabrics, the heat release tester WATson was developed to determine the cooling power. However, the measured cooling power is only a physical value. Without correlation of these physical values with data of subject trials, the cooling power do not give any information about the perception of the human body and the achieved cooling effect. Subject trials were made under controlled condition and typical use conditions. Results: The cooling power of various cooling textiles was measured with WATson; Controlled wearer trials in the climate chamber gives information about the perception and feeling of coolness. The correlation of the physical data and the data of wearer trials is the base to evaluate the new test device WATson. Conclusions: A new clothing physiological device was developed. The cooling power is a new material specific parameter. After correlation of the new test device with wearer trials the cooling power is combined with the cooling perception. WATson is a logical extension for the clothing physiological testing tool to determine the cooling and comfort of textiles.

Comparison of sixty-minute urine excretion to 24-hours in determining proteinuria at altitude.
PRESENTER: Kelsey E. Joyce

ABSTRACT. Introduction: Expeditionary research teams have relied on 24-hour urine collections to examine glomerular status (e.g. urinary alpha-1 acid glycoprotein (orosomucoid) excretion, uORM excretion, ug/min) during ascent, however, the nature of these collections can be impractical during an expedition. Utilising shorter-duration collections would be advantageous, although no data exists evaluating the validity of such collections at altitude. Therefore, the objective of the present study was to compare uORM excretion rates between 24-hour and short-duration (60 min) urine collections during an altitude expedition. Methods: Short-duration urine collections were performed over 60 minutes surrounding exercise experiments (immediately pre-, post-120, and post-180) while at the Whymper Hut (5035m), Mt Chimborazo, Ecuador with ample time (> 60min) allotted to eliminate any post-exercise effect. Samples were aliquoted and frozen (on dry ice), transported back to the UK, then stored at -80 degrees C until analysis. Urinalysis was performed using a latex-enhanced immunoassay on the Optilite turbidimetric analyser (The Binding Site, Ltd., Birmingham, UK; measuring range: was 0.077 to 148.2 mg/L; analytical time 10 mins). Friedman’s test was use to compare uORM excretion between 24-hour and multiple 60-min samples (chi square, p<0.05), with post hoc Wilcoxon’s signed rank tests (Z score, p <0.025) performed where appropriate. Results: On average, the 60-min samples underestimated 24-hour uORM excretion by ~0.25ug/min surrounding exercise experiments, albeit, insignificantly (X2(3)=2.66, p=0.45). Mean percent error (accuracy) of the 60-min samples was 42%. Conclusion: Although comparable, 60-min urine sample collections obtained during the day underestimate 24-hour uORM excretion at altitude. We speculate that the reason for this underestimation may be attributable to other events across the 24-hour period where higher protein excretion/filtration and altered glomerular status may occur, such as during the night when oxygenation is worst with sleep-related changes in breathing patterns (e.g. apnoea). Performing early morning urine collections is required to confirm this hypothesis.

Maximum Exposure Time while Wearing Protective Clothing in Extreme Hot and Humid Environment

ABSTRACT. Introduction: Due to climate change in the world, the frequency and intensity of heat waves have been increasing. Since weather observation started in Korea, the maximum air temperature and relative humidity were recorded 39.6oC and 95%RH in 2018 summer, respectively. This study examined maximum exposure limit time under extremely hot and humid environments while wearing protective clothing. Method: Nine males (21.3±2.6 yr in age, 175.2±4.0 cm in height, and 70.1±7.9 kg in weight) participated in this study. A trial consisting of a 10-min rest was followed by 60-min of walking at a 4 km∙h-1 (135 W∙m‑2) and by 10-min of recovery. Subjects were exposed to the following six conditions in random order: air temperatures (Tair) of 28, 33, 38oC with 70%RH, with clothing condition of summer wear (SW) and protective clothing (PC, Level D). During all trials, rectal temperature (Tre), heart rate (HR) and subjective perceptions were recorded.  Results: Tre showed significant differences between clothing conditions in recovery period at 33oC (SW: 37.4±0.2, PC: 37.7±0.3oC, P=0.04) and at 38oC condition (SW: 38.2±0.2, PC 38.5±0.3oC, P=0.016). Increases in HR were significantly greater for PC than for SW at 33oC (SW: 26±15, PC: 46±8 bpm, P=0.003) and at 38oC (SW: 59±10, PC: 75±13 bpm, P=0.003). During recovery at 38oC, Tre continued increasing and HR was not recovered. Thirst sensation showed no significant difference between 28oC and 33oC conditions, but participants expressed very severe thirst sensation for both 38oC conditions (P<0.05). At the 38oC-PC condition, five of nine subjects abandoned the experiment due to dizziness or nausea (cessation time 54±3 min), while this was not the case for subjects in the 80-min exposure of the other five conditions. Conclusions: Healthy young workers wearing protective clothing under extremely hot and humid environments should not be exposed longer than 50 min and should take a longer recovery than 20 min after a bout of work. A more elaborative analysis will be following. Further studies with higher levels of PC and metabolic rates are required.

Comparisons of Core Body Temperatures during 7-Hour Sleep: Rectal at 6, 10, 14 cm Depth, Ear Canal, and Sublingual Temperatures

ABSTRACT. Introduction: The on-going debate concerning which body site is the most appropriate for thermal core measurement has remain unresolved. While substantial studies have been documented comparing different measurement methods at rest or during exercise, little research explored differences between core body temperature measurements in sleep. This study aimed to compare body temperature of different body sites as measurements of core body temperature during a 7-hour sleep considering rectal temperature at the deepest depth as a gold standard. Method: Nine females participated in the experiment 48 hours after a first night of sleep to adapt to the new sleeping environment. The bedroom was maintained at Tair of 27oC and 50%RH. Subjects slept from 00:00 AM to 07:00 AM. Rectal temperature (Tre) at 6, 10, 14 cm depth, ear temperature (Tear), heart rate, sleep variables were monitored throughout the night. Sublingual temperature (Tsublingual) was measured before and after sleep. Results: Average Tre at 14 cm depth during sleep was 36.6 ± 0.3oC. Average Tre at 6 and 10 cm were 36.3 ± 0.5oC and 36.5 ± 0.3oC, respectively, without any statistical difference from the 14 cm value. Average ear canal temperature (36.3 ± 0.4oC) was significantly lower than Tre at 14 cm depth (P<0.05). Before sleep, Tre at 6 cm depth (36.6 ± 0.3oC) and sublingual temperature (36.6 ± 0.3oC) was significantly lower than Tre at 10 (36.8 ± 0.3oC) and 14 cm (36.9 ± 0.3oC) depth (P < 0.05). After sleep, both Tear (36.2 ± 0.4oC) and Tsublingual (36.3 ± 0.3oC) were significantly lower than Tre at 14 cm depth (36.5 ± 0.3oC) (P < 0.001). Conclusions: During sleep, Tre at 10 and 14 cm depth showed the highest and the most stable values whereas Tre at 6 cm depth and Tear seemed to be more influenced by the ambient temperature.

Validation of Wearable Blood Pressure Monitor in the Hypertensive Elderly
PRESENTER: Joonhee Park

ABSTRACT. Introduction: Of late, the smart watch for measuring blood pressure has become popular. It has proven especially useful for hypertensive individuals. However, there were few studies on the effectiveness of wearable blood pressure monitors for hypertensive individuals. We examined the effectiveness of a recently developed blood pressure watch for measuring blood pressure as well as pulse frequency in hypertensive elderly individuals. Method: Twenty-two older males (76.2±4.0 yr) and 22 older females (73.1±5.7 yr) participated in this study. The experiment was conducted in a climatic chamber (an air temperature 20.0±0.1oC with 51±2% RH) for 150 min. During the initial 60 min, subjects’ blood pressure was measured while they were kept comfortable (estimated clothing insulation of 1.1 clo [Icl]). After that, they took off all their outer garments and socks, and wore only underwear, short-sleeved T-shirts and half-length pants (0.3 clo estimated) during the 90 min. Two other types of sphygmomanometers (automatic digital blood pressure monitor [OM] and manual sphygmomanometer of aneroid type [AS]) were compared with the smart watch (WS). Blood pressures and pulse frequency were measured three times with each sphygmomanometer during the initial and last 60 min of the 90 min, respectively. Results: Systolic and diastolic blood pressures in WS were higher than those in OM and AS (P<0.01). Also, the Bland-Altman plots of WS and OM or AS had wider ranges in the 95% limit of agreement (LoA), while OM and AS had narrow range in 95% LoA and showed uniform distribution without any tendency. However, WS and OM in pulse frequency showed good precision, narrow ranges in 95% LoA and uniform distribution. Conclusions: When compared to automatic or manual sphygmomanometers, the smart watch has limited application as blood pressure monitor while it measures pulse frequency accurately for the hypertensive elderly.

Thermal Insulation of Padded Winter Jackets according to Design and Materials

ABSTRACT. Introduction: Clothing weight has been reported as the main determinant of thermal insulation. In Korea, lighter and warmer padded winter jackets have been popular in recent years because of newly developed light weight winter fabrics along with various types of down materials. However, few studies report the thermal insulation of the padded winter jackets. This study examined the thermal insulation of padded winter jackets using a thermal manikin to provide appropriate guidelines for selection. Method: Eighteen padded jackets commercially available were tested on a dry thermal manikin at an air temperature of 20oC with 50%RH (ISO 9920, 2007). The padded jackets consisted of various designs [66 ~ 113 cm in garment length, 0.28 ~ 1.57 kg in garment weight, 60 ~ 62 cm in sleeve length, 49 ~ 52 cm in chest width], outer covering materials [polyester (10 jackets) or nylon (8 jackets)], filling materials [10 jackets with goose down and 8 jackets with duck down], and lining materials [polyester (10 jackets) or nylon (8 jackets)]. Results: The thermal insulation (Iclu) of padded jackets was 0.589 ± 0.289 clo (0.342 ~ 1.271 clo) and positively correlated with garment length (r=0.945, p<0.0001), garment weight (r=0.651, p=0.003), and covering area (r=0.614, p=0.007). The Iclu of a padded jacket can be estimated using the following equation: 0.014×garment length(m)-0.534 (corrected R2=0.893, p<0.001). The thermal insulation of duck down padded jackets was greater than that of goose down padded jackets, over a certain weight. There were no significant differences in the thermal insulation of padded jackets according to the mixture ratio of chest down (beneath feathers) or feathers (outer covering of birds) filling materials. Conclusions: Garment length was the major determinant of thermal insulation for padded winter jackets. Garment weight or covering area followed garment length. Testing the thermal insulation of synthetic filling is necessary and it will follow up on the next research.

Fiber-pore-structure of outdoor clothing

ABSTRACT. Introduction: In an experimental study, data about arrangement and distribution of fibers and pores around the dressed human body are derived. Backgrounds are investigations about temperature regulation of outdoor clothing. Method: The pore size distributions of knitted and woven textiles from PES and PA yarns are derived from geometry and physical fiber, yarn and fabric properties with aid of mathematical equations. From these materials, two outdoor clothing systems are made to measure for five test persons. With scanner and fit simulation methods, distances between human body and different clothing layers are individually determined. Results: In the volume balance, the outdoor clothing systems investigated consist of about 3 to 7 % fibers, 5 to 20 % yarn or meso pores, 5 to 20 % textile or macro pores and 50 to 90 % clothing pores. In absolute terms the volume of the fibers are about 500 to 2,000 cm3, of the yarn and textile pores about 600 to 6,000 cm3 each and of the clothing pores about 14,000 cm3. Conclusions: As premise for further investigations, the quantity of micro, meso, macro and mega pores significantly affects temperature regulation properties of outdoor clothing.

Moisture accumulation in sleeping bags and sleep quality in warm and cold bivouac during eight days military ski march.

ABSTRACT. Introduction: In the Norwegian Military soldiers will usually stay in tents which are heated during winter operations (warm bivouac).The soldiers take care of and guard the heating device and usually they take one to two hours heating guard each during the night. An improved quality of the sleeping bag and mattress give the possibility to stay overnight in the tents without heating (cold bivouac) and in this way probably increases the sleep quality. However, the accumulation of moisture in the sleeping bag system may probably increase in the cold bivouac compared to the warm one. The objective of the study was to compare both the moisture accumulation in the sleeping bag system and the sleeping efficiency in warm and cold bivouac. Method: Two squads, with six soldiers in each, were divided into two tents, with and without heating. The sleeping bag system with both sleeping bag and overbag were weighted both before the first night and just after the last night. The sleeping efficiency was measured by accelerometer Actigraph on the wrist all the time. The study was conducted in February and the ambient night temperature varied from – 6 to – 17 °C. Results: The moisture accumulation in the sleeping bag systems increased significantly in both the cold and the warm bivouac with 11 and 5 % respectively but the difference was not significant. The mean sleep efficiency for the cold and warm bivouac was 88-96 % and 70-82 % respectively during the eight nights and was significant for the 6th and the 8th night. Conclusions: The moisture accumulation in the sleeping bag systems increased in both cold and warm bivouacs and it increased more in the cold bivouac, but not significantly more. The sleeping quality was significantly better in the cold bivouac.

Development of thermoregulation model and thermal comfort model based on neurophysiology

ABSTRACT. A multi-segmented model based on neurophysiology was developed to predict regulatory dynamic responses and physiological variables of a clothed person in non-uniform transient environment. This model consists of two systems, i.e. the passive model and the active model. The passive one is that of Wissler’s model (2018). It splits the body into 21 cylindrical segments. Each segment is divided into 21 of which 15 for body tissues and 6 for clothes of covered skin. The production of heat is ensured by the metabolism within the body tissues and the heat exchange with the environment is established by convection and radiation. The active system consists of three main components: the thermoreceptors, the control center and the afferents. Local skin and core temperatures are transduced into neural impulse responses by cold and warm thermoreceptors. The hypothalamus receives these responses and sends neural drives to the afferents. At this level, the neural drives are transformed into physiological mechanisms such as vasomotion, shivering and sweating to maintain thermal homeostasis. This model is coupled to another one based on Zhang’s model (2003). It is dedicated to assessing thermal sensation and thermal comfort level of occupants in indoor environments. A comparison is made between our thermoregulation model and the original one of Wissler. Our thermal comfort model is also compared to the static model (PMV) and the dynamic thermal sensation model proposed by Fiala (1998).

A New Method to Capture the Dynamic Liquid Transport on Fabrics Using a Sweating Guarded Hot Plate and Thermal Imaging Camera

ABSTRACT. Introduction: Liquid transport on fabrics is essential to wear comfort. When humans sweat, an ideal fabric should have the ability to transport liquid from the skin surface quickly and to dry fast to minimize the discomfort sensation caused by sweat while optimizing cooling. The way the liquid interacts with the fabric and the skin can affect wearer’s thermal and tactile wet comfort. In this study, a new method to capture the dynamic liquid transport process on fabrics was developed. Method: A sweating guarded hot plate was used to provide a steady liquid and heat source to the fabrics and to measure the total heat loss. During the test, the fabric sample was placed on the heated plate (35℃) and a total of 0.8ml distilled water was supplied to the fabric sample (10x10cm) through four sweat pores of the plate. A thermal imaging camera and a cell phone camera were set on top of the fabrics to simultaneously record the dynamic wetting and drying process. Results: The corresponding thermal and regular video indicated that there are different liquid spreading and drying patterns among different fabrics. By analyzing the corresponding videos, a sticking effect was identified between the wetted fabrics and the heated plate in some wool and polyester knitted fabrics. The maximum wetted area of each fabric was identified by utilizing ImageJ software. Conclusions: The development of this method provided a new way to capture the dynamic liquid transport process on fabrics and is helpful in characterizing wetting and drying properties of textile materials for assessing wet thermal and tactile comfort on the skin. Furthermore, the method provides better insight in the determining factors of comfort of wet fabrics on the skin.

Improving Individualized Thermal Exposure Warning and Advising Systems via User Feedback

ABSTRACT. The smartphone application ClimApp (freely available in Google Play and App Store) has been developed to integrate climate service data (weather forecasts) with individual physiological characteristics to provide personalized alerts and advice during challenging thermal conditions. This presentation will provide an overview of the implementation of an adaptive feedback system that has been integrated in ClimApp to optimize the level of individualization and improve accuracy in the alert-advice system based on feedback from the user.

ClimApp combines individual user characteristics, human thermal models and weather forecast data in a mobile application with the goal to provide protective strategies for an individual. The decisions are based on output from models for heat (WBGT ISO7243, PHS ISO7933), comfort (PMV ISO7730) and cold (IREQ ISO11079). By calculating the recommended alert limit (RAL), a heat risk indicator is provided to the user to indicate the severity of the exposure accompanied by textual advice on how to act in the current situation. The expected thermal strain may vary between individuals due to differences in anthropometric characteristics such as height, weight and sex but also as a consequence of different levels of adaptation. Therefore, to fully customize advice to the individual, population-averaged output from models will be insufficient, and feedback could be used to tune the advice to the individual demand. Examples of individualization at higher resolution will be presented and discussed along with the benefits of prompting users for feedback in situations that were perceived as more extreme than what the app advice may have indicated on a particular day. This is expected to allow for assessment and updating of individualized adaptation strategies suggested by ClimApp to promote better coping strategies and further improve individual health and performance of people exposed to thermally stressful conditions.

Maintenance of high physical fitness by firefighters in Poland

ABSTRACT. Introduction: In Poland, firefighters obtain recommendations to maintain physical fitness which is assessed during annual fitness checks. However, access to exercise rooms and exercise equipment varies across individual fire departments. Most often, firefighters train on their own without having an exercise plan. They train favorite sport disciplines. Method: A physical training plan for firefighters had been prepared, including strength and efficiency exercises with the use of a few exercise equipment items. An 8 week test training, organised in 90 minute sessions, occurring twice a week, was carried out. Younger (25-35 years old) and older (36-45 years old) firefighters, 11 participants in each group, took part in the training. Before starting and after the completion of the entire training cycle, fitness tests and physical performance tests were conducted. Subjective judgments regarding the effectiveness of the training were collected and body mass was registered. Results: Fitness tests showed better results by 17% to 39% depending on the exercise being performed. The level of physical efficiency has increased slightly, to a larger extent in the older group. Weight loss was recorded in the younger group of firefighters. Subjective assessments of the training were positive to a higher degree in the older group of firefighters. Conclusions: The conducted test training was used to verify the developed exercise plans. In the final version, the proportion of efficiency exercises was increased and a higher frequency of trainings was proposed, up to a minimum of 3 times a week. The developed program will be made available to every fire department in Poland.

Combined effects of low-dose ice slurry ingestion and forearm cooling on thermoregulation and physical capacity during exercise in hot environments
PRESENTER: Koji Muraishi

ABSTRACT. Introduction: Although both ice slurry ingestion and forearm cooling are practical strategies to prevent hyperthermia, no research has examined the combined effects of these two on thermoregulation and exercise capacity. The aim of the present study was to determine the combined effects of low-dose ice slurry ingestion and forearm cooling on thermoregulatory responses and exercise capacity in hot environments. Method: Seven male subjects underwent four experimental trials at 35 °C and 60% relative humidity. The experimental trials consisted of cycle exercise at 55% maximal oxygen uptake (first exercise bout) until rectal temperature reaches 38.5 °C. At the end of the first exercise bout, subjects conducted a 15 min recovery period before continuing with exercise to exhaustion at 75% maximal oxygen uptake (second exercise bout). The four recovery periods were performed under the following conditions: only passive rest (CON), only ice slurry ingestion (SLU), only forearm immersion (ARM), and ice slurry ingestion combined with forearm immersion simultaneously (MIX). Results: Rectal temperature was significantly lower (P<0.05) at the end of the recovery period in MIX compared with CON (MIX: -0.4 ± 0.3 °C, ARM: -0.3 ± 0.2 °C, SLU: -0.2 ± 0.2 °C, CON: 0.0 ± 0.2 °C). Mean skin temperature and subjective rating change was significantly lower (P<0.05) during recovery period in MIX and ARM compared with CON and SLU. However, exercise time to exhaustion was longer (P<0.05) in SLU compared with CON and MIX (SLU: 11.4 ± 4.0 min, ARM: 8.8 ± 2.4 min, MIX: 8.1 ± 3.1 min, CON: 5.7 ± 1.4 min). Conclusions: These results suggest that ice slurry ingestion combined with forearm immersion during recovery period was effective in suppression of hyperthermia, but not effective on the exercise capacity in the heat.

15:30-17:18 Session 10: Vulnerable populations
Influence of age on perceptual responses to thermal stress at rest and following exercise
PRESENTER: Alison Millyard

ABSTRACT. Introduction: Studies have shown that older adults are less able to dissipate heat during exposure to high environmental temperatures. Recent work has indicated that older adults may also be less able than younger adults to implement protective behavioural changes during exercise in the heat, increasing their risk of heat illness. Method: This study employed a randomised crossover design using Cool (22°C, 40% RH) and Hot (35°C, 40% RH) environmental conditions to compare thermoregulatory behaviour between young (18-35 yrs, n=10) and older (≥65 yrs, n=14) adults during 3 x 10 min of walking at a rating of perceived exertion (RPE) of 13. After a baseline visit including familiarisation with RPE, participants completed two experimental trials, (Cool and Hot). Participants sat at rest for 45 min upon entering the environmental chamber, after which they began walking on a motorised treadmill. Speed was blinded from participants and self-selected to elicit an RPE of 13. Distance (km) walked during each bout was recorded. Rectal temperature (Trec, °C) and heart rate (HR bpm) were recorded every 5 min. Results: Markers of physiological strain between the Cool (22.1 ± 0.29°C, 42 ± 5% RH) and Hot (35.1 ± 0.23°C, 41 ± 5% RH) trial increased for the older (HR 80 v 93 bpm, p<0.01; Trec 37.03 v 37.85 °C, p<0.01) and younger group (HR 91 v 98 bpm, p<0.05; Trec 37.57 v 37.99 °C, p<0.05). The older and younger group reduced their total distance walked by 1.5% and 8.0% respectively. Within the older group, a gender difference was evident with the women (n=5) walking 6.7% less distance in the heat, but the men (n=9) walked 1.5% further in the heat. Conclusions: Older adults, particularly men, appear to be less able to adapt their behaviour during heat stress, resulting in an increased thermal and physiological strain.

Upgrading a thermo-physiological model to predict children skin temperatures in cold environments

ABSTRACT. Introduction: Sports clothing for children are currently designed using adult-based knowledge, without any certainty about their real performances in terms of thermal comfort. As far as we know, existing thermo-physiological models do not include children specificities yet. This is why Decathlon’s Thermal Laboratory decided to upgrade the Fiala Physiology and Comfort (FPC) Model (ErgonSim) in order to take into account children anthropometry and thermal regulation.

Method: 8 years old boy and girl anthropometric parameters (heights, body regions dimensions, weights, body mass index, and body fat contents) were implemented in the model according to Decathlon’s own database. Basal metabolic rates and thermoregulatory responses (sweating, shivering, peripheral vasodilatation and constriction) were adapted for children using available literature data. An experimental study was carried out at Loughborough University involving 9 children (8.4 ± 1.0 years old) walking at 30% VO2max on a treadmill in a climatic chamber set at 4 ambient temperatures (2°C / -5°C / -12°C / -19°C). VO2 uptakes and skin temperatures (forehead, cheek, chest, back, arm, hand, quadriceps, shin and foot) were recorded for each subject. Thermal resistances of the 3 layers clothing ensemble worn were measured using Thermetrics Jordi manikin (16 body regions). The experimental protocol was simulated using the adapted FPC model to compare experimental results with predictions.

Results: Skin temperatures were predicted quite well for covered regions (hands excluded) but not for nude regions (see table). Mean skin temperature was also predicted well, with less than 1°C difference from measurements on average, despite an offset of 2°C at the beginning of the scenario (see figure).

Absolute differences (in °C) between measured and simulated skin temperatures (Tair = -19°C) Forehead Cheek Chest Back Arm Hand Quadriceps Shin Foot Mean skin Average 6.3 5.6 1.0 1.1 3.6 3.1 0.3 1.1 0.9 0.9 Min 1.8 1.4 0.0 0.0 2.5 0.1 0.0 0.0 0.0 0.0 Max 8.9 9.6 1.6 1.9 4.9 7.8 1.4 2.3 2.2 1.9

Mean skin temperature (in °C) comparison between measurement and simulation (Tair = -19°C)

Conclusions: First results of the modified model are quite promising. Mean skin temperatures for children in cold environments can be well predicted, which will surely provide new means to evaluate clothing thermal performances. Metabolic rates could be adjusted to improve model accuracy, reducing local differences between predictions and measurements.

Extended post-exercise hyperthermia in the heat in athletes with a spinal cord injury

ABSTRACT. Rationale: Hyperthermia most often occurs during exercise, however athletes with a spinal cord injury (SCI) may also be at risk post-exercise due to impaired thermoregulatory function. This study investigated the influence of SCI level on thermoregulation post-exercise in the heat. Methods: 8 tetraplegic (TP), 7 high paraplegic (HP), 8 low paraplegic (LP) and 8 able-bodied participants (AB) rested for 45 min in 35°C and 50% RH, following exercise at a metabolic heat production of 4 W/kg (TP, AB) or 6 W/kg (HP, LP, AB). Gastrointestinal (Tgi) and esophageal (Tes) temperature, local sweat rate (LSR) and cutaneous vascular conductance (CVC) at the forehead and back, and forearm blood flow (FBF) were assessed. Results: Tgi in TP increased throughout recovery whereas in AB it reduced, reaching 38.77°C (95% CI: 38.63, 38.91) and 37.07°C (36.93, 37.21) respectively after 45 min (p<0.001). Similarly, Tes was highest after 45 min for TP (38.34°C [38.20, 38.48]) but lowest for AB (36.58°C [36.45, 36.71]). Immediately post-exercise, AB had a greater forehead LSR (0.76 mg·cm-2·min-1 [0.68, 0.84]) and back LSR (0.57 mg·cm-2·min-1 [0.52, 0.61]) compared to TP who exhibited no sweating (p<0.001). TP had greater forehead CVC (p=0.013), back CVC (p=0.044) and FBF (p=0.002) than AB. Immediately post-exercise at 6 W/kg, Tgi and Tes reduced in AB, LP and HP. HP consistently demonstrated higher Tgi and Tes (p<0.001), despite greater forehead and back LSR relative to LP and AB (p<0.001), and greater back CVC than AB (p=0.029). Conclusions: Both core temperature indices continued to rise post-exercise in TP, due to a lack of sweating and dry heat transfer. Greater LSR and CVC post-exercise in HP does not fully alleviate their higher core temperature compared to LP and AB, who demonstrate a similar return to baseline values. HP and particularly TP athletes are at greater risk of post-exercise hyperthermia.

Preliminary evidence of sex-related differences in the effect of aging on whole-body heat loss during exerise in dry-heat

ABSTRACT. Introduction: During vigorous exercise in dry-heat, young females display attenuated whole-body total heat loss (evaporative ± dry heat exchange) relative to males (J Appl. Phsiol., 2012, 113(5):746). Similarly, older males and females demonstrate marked reductions in total heat loss relative to their younger counterparts during moderate-to-vigorous exercise in a hot-dry environment (Compr. Physiol., 2013, 3(4):1689). However, the interactive effect of sex and age on total heat loss during exercise in the heat remains unexplored. Given that older females are known to be at a greater risk of heat-related mortality compared to males, it is possible that the age-related decline in heat loss is accelerated in females relative to males. We therefore sought to evaluate this hypothesis. Method: 24 young (18-30 years; 12 males, 12 females) and 24 older (50-65 years; 12 males, 12 females) habitually active adults completed three, 30-min bouts of semi-recumbent cycling at increasing metabolic heat productions of 150 [Light], 200 [Moderate], and 250 [Vigorous] W/m2 (equivalent to ~30/37%, 42/49%, and 53/61% VO2peak in young/older adults), each seperated by 15-min recovery, in dry heat (40°C, ~15% relative humidity). Metabolic heat production and total heat loss were measured using indirect and direct calorimetry, respectively. Results: The effect of age on total heat loss was dependent upon sex during light, moderate, and vigorous exercise (all p<0.05), such that total heat loss was 15, 14, and 16% lower in older compared to young females. In contrast, older males demonstrated a 12% reduction in total heat loss relative to young males during vigorous exercise only (p<0.05). Conclusions: Our preliminary findings indicate that females demonstrate a greater age-related decline in whole-body heat loss relative to males, which may explain, at least in part, the increased heat-related mortality in older females. Funding support: Natural Sciences and Engineering Research Council of Canada

An evaluation of whole-body heat exchange in older adults exposed to extreme day-long heat.

ABSTRACT. Introduction: Investigations into the physiological strain experienced by older adults during extreme heat events (EHE) have typically employed short-duration exposures (≤3 hours), even though EHE occur over extended periods. This study was therefore designed to advance our understanding of whole-body heat exchange and the development of hyperthermia during a day-long exposure to EHE-like conditions.

Method: Five young (22 [SD 2] years; one woman) and six older (70 [3] years; two women) adults rested in ambient conditions of 40°C (10% relative humidity) for nine hours; representative of exposure conditions experienced during EHE. During the initial and final three hours, the rate of body heat storage was assessed as endogenous heat production (indirect calorimetry) minus whole-body heat loss (direct calorimetry). Rectal temperature was monitored continuously.

Results: Young adults achieved heat balance (heat storage = 0 W) during the nine-hour exposure (hour three: -1 W [95% CI: -6-4]; hour nine: 5 W [-4-14]). Conversely, heat balance was not achieved in the older adults, as evidenced by a positive rate of heat storage at the end of the initial (7 W [3-10]) and final three hours (8 W [1-15]). Rectal temperature was elevated from pre-exposure values (young: 37.03°C [0.29]; older: 36.89°C [0.26]) by 0.52 (0.46-0.58) and 0.97 (0.67-1.37) in the young (37.55°C [0.28]) and older (37.83°C [0.47]) adults, respectively, at hour three. However, while rectal temperature had not changed (0.10°C [-0.18-0.34]) from the three-hour value in the young (37.65°C [0.20]) at hour nine, an additional 0.23°C (0.11-0.45) increase was seen in the older group (38.07°C [0.15]).

Conclusions: These preliminary outcomes indicate that during exposure to EHE-like conditions, older individuals do not achieve heat balance and experience progressive hyperthermia. Data gleaned from short-duration exposures (≤3 hours) may underrepresent the physiological strain, and therefore risk of adverse health events, incurred by older adults during EHE.

Funding: Canadian Institutes of Health Research.

Development of a methodological approach used to assess comfort and thermal tolerance of children exercising at zubzero temperatures
PRESENTER: Leigh Arlegui

ABSTRACT. Introduction: Human thermoregulatory models along with thermal sensation data have been effective predictors of thermal comfort for adults, however, the differences in thermoregulatory responses and thermal perception in children questions the validity of using adult-based models to predict children’s thermal comfort. This study aimed to test the methodological approach designed to collect human data necessary to assess and model thermoregulatory responses and thermal comfort of children. Method: A heavily insulating clothing combination was tested at 2, -5, -12 & -19℃ and lighter clothing at 16, 9, 2 & -5℃ (wind speed <0.3m/s, relative humidity <50%, no solar radiation). Anthropometrics were taken and a submaximal test on the treadmill performed. Pre-pubescent participants dressed into the assigned clothing and walked continuously at a relative intensity of 35% VO2max for up to 60 minutes in the climatic chamber. Heart rate (bmp), oxygen uptake (ml/min/kg), clothing microclimate (℃, %) and skin temperature at 9 body sites (℃) were measured, thermal comfort (yes/no), sensation and preference (-3 to +3) ratings were asked every 10 minutes. Additionally, 15-minute pre- and post-cold exposure data were collected. Results: This methodology allowed to determine the ambient temperatures at which pre-pubescent children were most thermally comfortable in, by establishing the limits of hot and cold discomfort in each clothing combination. Preliminary data show that participants (n=9) were most thermally comfortable at -12℃ in the heavily insulated clothing (62.5% were in comfort, 12.5% in hot discomfort and 25.0% in cold discomfort). In lighter clothing (n=7) the most comfortable temperature was 2℃ (85.7% were in comfort, 14.3% were in hot discomfort and 0% in cold discomfort). Conclusions: Providing specific data on thermal responses and comfort in children allows clothing companies to improve the design, and in the present application the communication of their products for children. Acknowledgements: Funding provided by Decathlon SportsLab.

High-resolution whole-body mapping of warm and cold thermosensitivity in people with multiple sclerosis

ABSTRACT. Introduction: Multiple sclerosis (MS) is a chronic autoimmune neurological disease affecting >2.5M people worldwide. Sensory symptoms (e.g. altered thermal sensations) are common in MS. However, data is lacking on whether and to what extent warm and cold sensitivity is impaired across the body in MS. The aim of this study was to map with high resolution warm and cold sensitivity across the body of people with MS and compare it to a control group. Methods: Fourteen people with MS (48±15y; BSA 1.94±0.25m2) and 9 age-matched healthy controls (CTR; 47±14y; BSA1.84±0.21m2) underwent a quantitative sensory test in a thermoneutral environment (24oC, 50%RH) where they rated on a numerical rating scale (10=very warm, 0=neutral, -10 very cold) local thermal sensations arising from the application (2s) of a warm (38oC) and a cold (26oC) thermal probe (1.32cm2) to 115 bilateral skin sites across the front and back of the body. We analyzed the independent effect of MS and body region on thermosensitivity and on its inter-individual variability (standard deviation). Results: Thermosensitivity to both warmth and cold varied significantly across body regions (p<0.01) with no differences between MS and CTR (warm-front: p=0.483, back: p=0.112; cold-front: p=0.552, back: p=0.517). Inter-individual variability was greater in MS than in CTR (warm-front MS=2.75±0.53, CTR=2.18±0.64, p<0.01; back MS=2.85±0.55, CTR=2.06±0.65, p<0.01) (Cold-front MS=2.97±0.61, CTR= 2.08±0.62, p<0.01; back MS= 2.96±1.12, CTR= 2.16±0.70; p<0.01). Conclusions: We have developed the most detailed thermosensitivity maps in MS to date and demonstrated that regional patterns of thermosensitivity are largely preserved in the presence of MS. Yet, we show that people with MS present greater individual variability in warm and cold sensitivity than CTR. Disability levels induced by MS likely contribute to a greater variability in regional patterns of thermosensitivity. This should be considered when assessing individual vulnerability to thermal stress in MS.

Delayed Time Course of Nitric Oxide-Dependent Reflex Vasodilation in Aged Human Skin

ABSTRACT. Introduction: Attenuated nitric oxide (NO)-dependent reflex vasodilation at a fixed rise in core temperature has been observed in aged skin; however, the temporal development of this impairment during whole body heating is unknown. We hypothesized that the NO contribution to reflex vasodilation would be attenuated in older versus young adults at each 0.1°C rise in oral temperature (Tor). We further hypothesized that the Tor threshold for NO-dependent dilation would be higher in older adults, but would be normalized with the administration of antioxidant or cofactor interventions. Method: Retrospective analysis of skin blood flow responses during whole-body heat stress (water-perfused suit) was performed for 11 young (22±1 yr) and 28 older (71±2 yr) participants under control, NO synthase-inhibition (20mM NG-nitro-L-arginine methyl ester; L-NAME), or intervention (local or systemic) conditions. Red cell flux was measured by laser-Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated (CVC=flux/mean arterial pressure) and expressed as a percentage of maximum (%CVCmax; 28mM sodium nitroprusside+43°C). NO-dependent dilation was calculated for each 0.1°C rise in Tor as the difference in %CVCmax between control/intervention and L-NAME sites. Results: NO-dependent dilation increased from baseline after a 0.2°C rise in Tor (p<0.01) in young, but after a 0.5°C rise (p<0.05) in older subjects. NO-dependent dilation was greater in young versus older subjects after a 0.2°C rise in Tor (all p<0.01). Intervention augmented NO-dependent dilation versus control at every Tor (all p<0.05) in older adults, but did not influence the threshold for NO-dependent dilation. Conclusion: In addition to previously reported attenuations in NO-dependent dilation in older adults during passive heating, these data suggest greater increases in core temperature are necessary to elicit NO-dependent dilation in the aged cutaneous vasculature. Local or systemic antioxidant or cofactor treatment augments NO-dependent dilation, but does not alter the temporal development of the response in older adults.

Inducing an inflammatory response in people with a disability; time to raise the temperature?

ABSTRACT. Introduction: The inflammatory response to a bout of exercise is suggested to exert beneficial effects on insulin signalling and chronic low-grade inflammation. However, severe disability, such as a cervical spinal cord injury (CSCI), may prevent individuals from inducing this response using exercise. As the increase in body temperature partly mediates the exercise-induced inflammatory response, passive heating may be a viable alternative to improve metabolic health in people with a disability. Methods: Here we present five studies investigating the efficacy of exercise and hot water immersion (HWI) to induce an inflammatory response in people with CSCI as well as able-bodied individuals. First, the acute interleukin-6 (IL-6) response to a wheelchair half-marathon and HWI was studied in people with CSCI. Thereafter, the acute and chronic effects of HWI on plasma IL-6 concentration and the expression of monocyte intracellular heat shock protein 72 (iHsp72) were investigated in able-bodied individuals, as well as its impact on fasting glucose and insulin concentration. Finally, an ex-vivo model was employed to further mechanistic understanding into the hyperthermia-induced acute inflammatory response. Results: The acute IL-6 response to exercise was markedly dampened in people with CSCI. However, in both able-bodied individuals and people with CSCI, HWI induced an acute IL-6 response. Neither the acute or chronic HWI-intervention increased iHsp72 expression. Nonetheless, fasting glucose and insulin were reduced following the chronic HWI-intervention. Incubation of whole blood at 40℃, but not 38.5℃, induced an acute iHsp72 response, suggesting that a large increase in core temperature is needed to elevate iHsp72 expression. Conclusions: The elevation of body temperature can independently induce an acute IL-6 response, while a chronic HWI-intervention may enhance glucose metabolism. Although its efficacy to alter iHsp72 expression requires further investigation, these findings may be exploited to create alternative health promoting strategies for people with a disability.