The effect of seasonal acclimatization on whole-body heat loss response during exercise in a hot humid environment with different air velocity

Seasonal acclimatization from winter to summer is known to enhance thermoeffector responses in hot-dry environments during exercise whilst its impact on sweat evaporation and core temperature (Tcore) responses in hot-humid environments remains unknown. We therefore sought to determine whether seasonal acclimatization is able to modulate whole-body sweat rate (WBSR), evaporated sweat rate, sweating efficiency and thermoregulatory function during cycling exercise in a hot-humid environment (32∘C, 75% RH). We also determined whether the increase in air-velocity, could enhance evaporated sweat rate and sweating efficiency before and after seasonal acclimatization. Twelve males cycled for 1-hour at 40% VO2max in winter (pre-acclimatization) and repeated the trial again in summer (after-acclimatization). For the last 20-min of cycling at a steady-state of Tcore, air-velocity increased from 0.2 (0.04) m/s to 1.1 (0.02) m/s by using an electric fan located in front of the participant. Seasonal acclimatization enhanced WBSR, unevaporated sweat rate, local sweat rate and mean skin temperature compared to pre-acclimatization state (all P<0.05) whilst sweating efficiency was lower (P<0.01) until the 55-min of exercise. Tcore and evaporated sweat rate were unaltered by acclimatization status (all P>0.70). In conclusion, seasonal acclimatization enhances thermoeffector responses but does not attenuate Tcore during exercise in a hot-humid environment. Furthermore, increasing air-velocity enhances evaporated sweat rate and sweating efficiency irrespective of acclimated state.

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Influence of air velocity and heat acclimation on human skin wettedness and sweating efficiency

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.6.1194 ◽

1979 ◽

Vol 47 (6) ◽

pp. 1194-1200 ◽

Cited By ~ 48

Author(s):

V. Candas ◽

J. P. Libert ◽

J. J. Vogt

Keyword(s):

Sweat Rate ◽

Water Vapor Pressure ◽

Thermal Conditions ◽

Heat Acclimation ◽

Air Velocity ◽

Experimental Conditions ◽

Wind Speeds ◽

Skin Wettedness ◽

Before And After ◽

Sweating Efficiency

Before and after heat acclimation, four male resting subjects were exposed to humid heat that caused levels of skin wettedness ranging from 50 to 100%. The physical experimental conditions were chosen so that the same skin wettedness was attained with modification of only the ambient water vapor pressure, at two wind speeds (0.6 and 0.9 m . s-1). The esophageal temperature (Tes), mean skin temperature (Tsk), sweating rate (msw), and dripping sweat rate (mdr) were recorded; the amounts of local drippage in the same thermal conditions before and after acclimation were also determined. The relationship between the evaporative efficiency of sweating (eta sw) and the skin wettedness (w) is reported, as is the influence of the subject's acclimation to humid heat on adjustments of skin wettedness. The effects of the air velocity on the coefficient of evaporation and on sweating efficiency are discussed. Beneficial increases in evaporation were achievable by increasing skin wettedness only when there was a consistent drippage, which differed from one body area to another and from one subject to another. The relation of drift in body temperature to skin wettedness changed with the acclimation of the subjects.

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Forearm cutaneous vascular and sudomotor responses to whole body passive heat stress in young smokers

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00079.2015 ◽

2015 ◽

Vol 309 (1) ◽

pp. R36-R42 ◽

Cited By ~ 8

Author(s):

Nicole E. Moyen ◽

Hannah M. Anderson ◽

Jenna M. Burchfield ◽

Matthew A. Tucker ◽

Melina A. Gonzalez ◽

...

Keyword(s):

Heat Stress ◽

Sweat Gland ◽

Sweat Rate ◽

Whole Body ◽

Mean Body Temperature ◽

Doppler Flowmetry ◽

Cutaneous Vasodilation ◽

Local Sweat Rate ◽

Vasomotor Activity ◽

Young Smokers

The purpose of this study was to compare smokers and nonsmokers' sudomotor and cutaneous vascular responses to whole body passive heat stress. Nine regularly smoking (SMK: 29 ± 9 yr; 10 ± 6 cigarettes/day) and 13 nonsmoking (N-SMK: 27 ± 8 yr) males were passively heated until core temperature (TC) increased 1.5°C from baseline. Forearm local sweat rate (LSR) via ventilated capsule, sweat gland activation (SGA), sweat gland output (SGO), and cutaneous vasomotor activity via laser-Doppler flowmetry (CVC) were measured as mean body temperature increased (ΔTb) during passive heating using a water-perfused suit. Compared with N-SMK, SMK had a smaller ΔTb at the onset of sweating (0.52 ± 0.19 vs. 0.35 ± 0.14°C, respectively; P = 0.03) and cutaneous vasodilation (0.61 ± 0.21 vs. 0.31 ± 0.12°C, respectively; P < 0.01). Increases in LSR and CVC per °C ΔTb (i.e., sensitivity) were similar in N-SMK and SMK (LSR: 0.63 ± 0.21 vs. 0.60 ± 0.40 Δmg/cm2/min/°C ΔTb, respectively, P = 0.81; CVC: 82.5 ± 46.2 vs. 58.9 ± 23.3 Δ%max/°C ΔTb, respectively; P = 0.19). However, the plateau in LSR during whole body heating was higher in N-SMK vs. SMK (1.00 ± 0.13 vs. 0.79 ± 0.26 mg·cm−2·min−1; P = 0.03), which was likely a result of higher SGO (8.94 ± 3.99 vs. 5.94 ± 3.49 μg·gland−1·min−1, respectively; P = 0.08) and not number of SGA (104 ± 7 vs. 121 ± 9 glands/cm2, respectively; P = 0.58). During whole body passive heat stress, smokers had an earlier onset for forearm sweating and cutaneous vasodilation, but a lower local sweat rate that was likely due to lower sweat output per gland. These data provide insight into local (i.e., forearm) thermoregulatory responses of young smokers during uncompensatory whole body passive heat stress.

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Hydration during Exercise in Warm, Humid Conditions: Effect of a Caffeinated Sports Drink

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.17.2.163 ◽

2007 ◽

Vol 17 (2) ◽

pp. 163-177 ◽

Cited By ~ 19

Author(s):

Mindy L. Millard-Stafford ◽

Kirk J. Cureton ◽

Jonathan E. Wingo ◽

Jennifer Trilk ◽

Gordon L. Warren ◽

...

Keyword(s):

Heart Rate ◽

Relative Humidity ◽

Sweat Rate ◽

Deuterium Oxide ◽

Serum Electrolytes ◽

Sports Drink ◽

Fluid Delivery ◽

Humid Environment ◽

Thermoregulatory Function ◽

Maximal Effort

Caffeine is regarded as a diuretic despite evidence that hydration is not impaired with habitual ingestion. The purpose of this study was to determine whether a caffeinated sports drink impairs fluid delivery and hydration during exercise in warm, humid conditions (28.5 °C, 60% relative humidity). Sixteen cyclists completed 3 trials: placebo (P), carbohydrate-electrolyte (CE), and caffeinated (195 mg/L) sports drink (CAF+CE). Subjects cycled for 120 min at 60–75%VO2max followed by 15 min of maximal-effort cycling. Heart rate and rectal temperature were similar until the final 15 min, when these responses and exercise intensity were higher with CAF+CE than with CE and P. Sweat rate, urine output, plasma-volume losses, serum electrolytes, and blood deuterium-oxide accumulation were not different. Serum osmolality was higher with CAF+CE vs. P but not CE. The authors conclude that CAF+CE appears as rapidly in blood as CE and maintains hydration and sustains cardiovascular and thermoregulatory function as well as CE during exercise in a warm, humid environment.

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Skin tattooing impairs sweating during passive whole body heating

Journal of Applied Physiology ◽

10.1152/japplphysiol.00427.2019 ◽

2020 ◽

Vol 129 (5) ◽

pp. 1033-1038

Author(s):

Maurie J. Luetkemeier ◽

Dustin R. Allen ◽

Mu Huang ◽

Faith K. Pizzey ◽

Iqra M. Parupia ◽

...

Keyword(s):

Sweat Rate ◽

Whole Body ◽

Sweat Glands ◽

Moderate Increase ◽

The Novel ◽

Cholinergic Stimulation ◽

Whole Body Heat Stress ◽

Reflex Control ◽

Body Heat ◽

Eccrine Sweat Glands

This study is the first to assess the reflex control of sweating in tattooed skin. The novel findings are twofold. First, attenuated increases in sweat rate were observed in tattooed skin compared with adjacent healthy non-tattooed skin in response to a moderate increase (1.0°C) in internal temperature during a passive whole body heat stress. Second, reduced sweating in tattooed skin is likely related to functional damage to the secretory mechanisms of eccrine sweat glands, rendering it less responsive to cholinergic stimulation.

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Exercise-rest cycles do not alter local and whole body heat loss responses

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00642.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. R958-R968 ◽

Cited By ~ 14

Author(s):

Daniel Gagnon ◽

Glen P. Kenny

Keyword(s):

Heat Loss ◽

Core Temperature ◽

Intermittent Exercise ◽

Sweat Rate ◽

Heat Content ◽

Whole Body ◽

Evaporative Heat Loss ◽

Esophageal Temperature ◽

Direct Calorimetry ◽

Body Heat

Previous studies have suggested that greater core temperatures during intermittent exercise (Ex) are due to attenuated sweating [upper back sweat rate (SR)] and skin blood flow (SkBF) responses. We evaluated the hypothesis that heat loss is not altered during exercise-rest cycles (ER). Ten male participants randomly performed four 120-min trials: 1) 60-min Ex and 60-min recovery (60ER); 2) 3 × 20-min Ex separated by 20-min recoveries (20ER); 3) 6 × 10-min Ex separated by 10-min recoveries (10ER), or 4) 12 × 5-min Ex separated by 5-min recoveries (5ER). Exercise was performed at a workload of 130 W at 35°C. Whole body heat exchange was determined by direct calorimetry. Core temperature, SR (by ventilated capsule), and SkBF (by laser-doppler) were measured continuously. Evaporative heat loss (EHL) progressively increased with each ER, such that it was significantly greater ( P ≤ 0.05) at the end of the last compared with the first Ex for 5ER (299 ± 39 vs. 440 ± 41 W), 10ER (425 ± 51 vs. 519 ± 45 W), and 20ER (515 ± 63 vs. 575 ± 74 W). The slope of the EHL response against esophageal temperature significantly increased from the first to the last Ex within the 10ER (376 ± 56 vs. 445 ± 89 W/°C, P ≤ 0.05) and 20ER (535 ± 85 vs. 588 ± 28 W/°C, P ≤ 0.05) conditions, but not during 5ER (296 ± 96 W/°C vs. 278 ± 95 W/°C, P = 0.237). In contrast, the slope of the SkBF response against esophageal temperature did not significantly change from the first to the last Ex (5ER: 51 ± 23 vs. 54 ± 19%/°C, P = 0.848; 10ER: 53 ± 8 vs. 56 ± 21%/°C, P = 0.786; 20ER: 44 ± 20 vs. 50 ± 27%/°C, P = 0.432). Overall, no differences in body heat content and core temperature were observed. These results suggest that altered local and whole body heat loss responses do not explain the previously observed greater core temperatures during intermittent exercise.

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Exercise-Induced Trace Mineral Element Concentration in Regional Versus Whole-Body Wash-Down Sweat

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.21.3.233 ◽

2011 ◽

Vol 21 (3) ◽

pp. 233-239 ◽

Cited By ~ 20

Author(s):

Lindsay B. Baker ◽

John R. Stofan ◽

Henry C. Lukaski ◽

Craig A. Horswill

Keyword(s):

Element Concentration ◽

Sweat Rate ◽

Sulfate Solution ◽

Skin Surface ◽

Cycle Ergometer ◽

Whole Body ◽

Air Chamber ◽

Local Sweat Rate ◽

Exercise Induced ◽

Sweat Composition

Simultaneous whole-body wash-down (WBW) and regional skin surface sweat collections were completed to compare regional patch and WBW sweat calcium (Ca), magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), and zinc (Zn) concentrations. Athletes (4 men, 4 women) cycled in a plastic open-air chamber for 90 min in the heat. Before exercise, the subjects and cycle ergometer (covered in plastic) were washed with deionized water. After the onset of sweating, sterile patches were attached to the forearm, back, chest, forehead, and thigh and removed on saturation. After exercise, the subjects and cycle ergometer were washed with 5 L of 15-mM ammonium sulfate solution to collect all sweat minerals and determine the volume of unevaporated sweat. Control trials were performed to measure mineral contamination in regional and WBW methods. Because background contamination in the collection system was high for WBW Mn, Fe, and Zn, method comparisons were not made for these minerals. After correction for minimal background contamination, WBW sweat [Ca], [Mg], and [Cu] were 44.6 ± 20.0, 9.8 ± 4.8, and 0.125 ± 0.069 mg/L, respectively, and 5-site regional (weighted for local sweat rate and body surface area) sweat [Ca], [Mg], and [Cu] were 59.0 ± 15.9, 14.5 ± 4.8, and 0.166 ± 0.031 mg/L, respectively. Five-site regional [Ca], [Mg], and [Cu] overestimated WBW by 32%, 48%, and 33%, respectively. No individual regional patch site or 5-site regional was significantly correlated with WBW sweat [Ca] (r = –.21, p = .65), [Mg] (r = .49, p = .33), or [Cu] (r = .17, p = .74). In conclusion, regional sweat [Ca], [Mg], and [Cu] are not accurate surrogates for or significantly correlated with WBW sweat composition.

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Impaired sweating responses to a passive whole body heat stress in individuals with multiple sclerosis

Journal of Neurophysiology ◽

10.1152/jn.00897.2016 ◽

2017 ◽

Vol 118 (1) ◽

pp. 7-14 ◽

Cited By ~ 9

Author(s):

Dustin R. Allen ◽

Mu Huang ◽

Iqra M. Parupia ◽

Ariana R. Dubelko ◽

Elliot M. Frohman ◽

...

Keyword(s):

Multiple Sclerosis ◽

Heat Stress ◽

Core Temperature ◽

Sweat Rate ◽

Whole Body ◽

Healthy Controls ◽

Cutaneous Vasodilation ◽

Whole Body Heat Stress ◽

Reflex Control ◽

Body Heat

Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system (CNS), disrupting autonomic function. The aim of this study was to test the hypothesis that individuals with MS have blunted control of thermoregulatory reflex increases in sweat rate (SR) and cutaneous vasodilation compared with controls during a passive whole body heat stress (WBH). Eighteen individuals with relapsing-remitting MS and 18 healthy controls (Con) participated in the study. Core temperature (Tcore), skin temperature, heart rate, arterial blood pressure (10-min intervals), skin blood flow (laser-Doppler flux, LDF), and SR were continuously measured during normothermic baseline (34°C water perfusing a tube-lined suit) and WBH (increased Tcore 0.8°C via 48°C water perfusing the suit). Following WBH, local heaters were warmed to 42°C, inducing peak cutaneous vasodilation at the site of LDF collection. Cutaneous vascular conductance (CVC) was calculated as the ratio of LDF to mean arterial pressure and expressed as a percentage of peak achieved during local heating. Individuals with MS had attenuated SR responses to WBH (ΔSR from baseline: Con, 0.65 ± 0.27; MS, 0.42 ± 0.17 mg·cm−2·min−1, P = 0.003), whereas Δ%CVC42C from baseline was similar between groups (Con, 42 ± 16%; MS, 38 ± 12%, P = 0.39). SR responses were blunted as a function of Tcore in MS (interaction: group × Tcore, P = 0.03), of which differences were evident at ΔTcore 0.7°C and 0.8°C ( P < 0.05). No interaction was observed in Δ%CVC42C. Taken together, the findings show MS blunts sweating responses, whereas control of the cutaneous vasculature is preserved, in response to WBH. NEW & NOTEWORTHY This study is the first to assess the reflex control of the thermoregulatory system in individuals living with multiple sclerosis (MS). The novel findings are twofold. First, attenuated increases in sweat rate in subjects with MS compared with healthy controls were observed in response to a moderate increase (0.8°C) in core temperature via passive whole body heat stress. Second, it appears the reflex control of the cutaneous vasculature is preserved in MS.

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Aspirin ingestion does not alter the onset or slope of local sweat rate during whole‐body passive heat stress (1104.12)

The FASEB Journal ◽

10.1096/fasebj.28.1_supplement.1104.12 ◽

2014 ◽

Vol 28 (S1) ◽

Author(s):

Stephen J. Carter ◽

Robert L. Herron ◽

S. Zeb Akers ◽

Ann B. Collins ◽

Jonathan E. Wingo

Keyword(s):

Heat Stress ◽

Sweat Rate ◽

Whole Body ◽

Local Sweat Rate ◽

Aspirin Ingestion

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Effects of varied air velocity on sweating and evaporative rates during exercise

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.6.2668 ◽

1992 ◽

Vol 73 (6) ◽

pp. 2668-2674 ◽

Cited By ~ 90

Author(s):

W. C. Adams ◽

G. W. Mack ◽

G. W. Langhans ◽

E. R. Nadel

Keyword(s):

Sweat Rate ◽

Body Weight Loss ◽

Cycle Ergometer ◽

Body Core Temperature ◽

Whole Body ◽

Air Velocity ◽

Sweat Loss ◽

Ergometer Exercise ◽

Sweat Production ◽

Total Body

This study was designed to determine the extent to which changes in the evaporative power of the environment (Emax) affect sweating and evaporative rates. Six male subjects undertook four 60-min bouts of cycle ergometer exercise at 56% maximal O2 uptake (VO2max).Emax was varied by differences in ambient temperature and airflow; two exercise bouts took place at 24 degrees C and two at 35 degrees C, with air velocity at < 0.2 and 3.0 m/s in both. Total sweat production was estimated from body weight loss, whereas whole body evaporative rate was measured continuously from a Potter beam balance. Body core temperature was measured continuously from a thermocouple in the esophagus (T(es)), with mean skin temperature (Tsk) computed each minute from thermocouples at eight sites. Total body sweat loss was significantly greater (P < 0.05) in the 0.2- than in the 3.0-m/s condition at both 24 and 35 degrees C. Tsk was higher (P < 0.05) in the still-air conditions at both temperatures, but final T(es) was significantly higher (P < 0.05) in still air only in the 35 degrees C environment. Thus the reduced Emax in still air caused a greater heat storage, thereby stimulating a greater total sweat loss. However, in part because of reduced skin wettedness, the slope of the sweat rate-to-T(es) relation at 35 degrees C in the 3.0-m/s condition was 118% that at 0.2 m/s (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

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