Chest Sweat Research Articles

The sweat glands' maximum ion reabsorption rates following heat acclimation in healthy older adults.

What is the central question to this study? Do the sweat glands' maximum ion reabsorption rates increase following heat acclimation in healthy older individuals and is this associated with elevated aldosterone concentrations? What is the main finding and its importance? Sweat gland maximum ion reabsorption rates improved heterogeneously across body sites, which occurred without any changes in aldosterone concentration following a controlled hyperthermic heat acclimation protocol in healthy older individuals. We examined whether the eccrine sweat glands' ion reabsorption rates improved following heat acclimation (HA) in older individuals. Ten healthy older adults (>65years) completed a controlled hyperthermic (+0.9°C rectal temperature, Tre ) HA protocol for nine non-consecutive days. Participants completed a passive heat stress test (lower leg 42°C water submersion) pre-HA and post-HA to assess physiological regulation of sweat gland ion reabsorption at the chest, forearm and thigh. The maximum ion reabsorption rate was defined as the inflection point in the slope of the relation between galvanic skin conductance and sweat rate (SR). We explored the responses again after a 7-day decay. During passive heating, the Tb thresholds for sweat onset on the chest and forearm were lowered after HA (P<0.05). However, sweat sensitivity (i.e. the slope), the SR at a given Tre and gross sweat loss did not improve after HA (P>0.05). Any changes observed were lost during the decay. Pilocarpine-induced sudomotor responses to iontophoresis did not change after HA (P≥0.801). Maximum ion reabsorption rate was only enhanced at the chest (P=0.001) despite unaltered aldosterone concentration after HA. The data suggest that this adaptation is lost after 7days' decay. The HA protocol employed in the present study induced partial adaptive sudomotor responses. Eccrine sweat gland ion reabsorption rates improved heterogeneously across the skin sites. It is likely that aldosterone secretion did not alter the chest sweat ion reabsorption rates observed in the older adults.

Sweating and cutaneous vasodilation responses above the lesion during passive heat stress in persons with thoracic spinal cord injuries

BackgroundSweating and cutaneous vasodilation responses in humans increase with an increase in body core and skin surface temperatures; a ratio of contributions is 10 to 1, respectively, via an excitation of sympathetic nervous system. However, these responses are absent or blunted on the skin below the lesion in persons with a spinal cord injury. The diminished thermoregulatory capacity may contribute to a decline in performance of a competition. In case of able‐body (AB) marathon, the optimum ambient temperature (Topt) to exert a competitiveness would be around 10°C and a race time tends to be worth once the temperature was over Topt. In our analysis from the past 20 years of the Oita International Wheelchair Marathon, a completion rate was ~8% in marathon and half‐marathon under ambient temperature (Ta) 18.3°C (13.3–26.3, min‐max) and relative humidity 63% (28–96). The rate tended to decrease the more with the more increased and decreased Ta on the both sides of 22°C. Thus, competitiveness in wheelchair athletes would be influenced from climate condition beyond developing wheelchair and Topt may not be the same as AB. Diminished thermoregulatory capacity in persons with a spinal cord injury relates their competitiveness and varies Topt. However, information for their thermoregulation is still necessary.ObjectivesSweat rate (SR) and cutaneous vasodilation responses to a thermal stress are absent in persons with a cervical spinal cord injury (CSCI) and are not observed distal to the lesion in persons with lower spinal cord injuries. It remains unknown whether the thermo‐effector responses above the lesion in spinal cord injuries are similar to AB, and related to the time since the injury.MethodsSeven persons with a thoracic spinal cord injury (TSCI; Th4‐10; time since injury 1–24 yrs) and 10 AB subjects participated in this protocol. While in the supine position, 33‐°C water was circulated through a water‐perfused suit worn by each subject. After 30‐min rest, 10 min of baseline data were obtained. Then, 36‐ and 50‐°C waters were perfused through the upper and lower parts of the suit, respectively, until esophageal temperature increased by 1°C.ResultsThe heat stress increased cutaneous vasodilation and SR on the chest (C4; sensate skin for SCI) in both groups. However, the increase in these variables was suppressed in LSCI. Moreover, the magnitude of the increase in chest SR at the end of heating was positively related to the time since the injury in LSCI (r=0.98; P&lt;0.0001).ConclusionSweating and cutaneous vasodilation responses at 1‐°C increase in esophageal temperature above the lesion are suppressed in LSCI and sweating responses is possibly affected by time since the injury. The impaired thermoregulatory responses may be associated with the completion rate in a wheelchair marathon.Support or Funding InformationThis study was funded by the Research Foundation of NachiKatsuura City, the Nakatomi Foundation, and National Heart, Lung, Blood Institute Grant HL‐61388.

Effects of Casein Hydrolysate Ingestion on Thermoregulatory Responses in Healthy Adults during Exercise in Heated Conditions: A Randomized Crossover Trial.

Food ingestion has been shown to affect thermoregulation during exercise, while the impact of protein degradant consumption remains unclear. We investigated the effects of casein hydrolysate ingestion on thermoregulatory responses during exercise in the heat. In a randomized, placebo-controlled, double-blind, crossover trial, five men and five women consumed either 5 g of casein hydrolysate or placebo. Thirty minutes after ingestion, participants cycled at 60% VO2max until voluntary exhaustion wearing a hot-water (43 °C) circulation suit. Exercise time to exhaustion, body core temperature, forearm sweat rate, and forearm cutaneous vascular conductance did not differ different between the conditions. However, chest sweat rate and mean skin temperature increased upon casein hydrolysate ingestion compared with placebo during exercise. Increased chest sweat rate upon casein hydrolysate ingestion was associated with elevated sudomotor sensitivity to increasing body core temperature, but not the temperature threshold for initiating sweating. A positive correlation was found between chest sweat rate and plasma total amino acid concentration during exercise. These results suggest that casein hydrolysate ingestion enhances sweating heterogeneously by increasing peripheral sensitivity of the chest’s sweating mechanism and elevating skin temperature during exercise in the heat. However, the physiological link between plasma amino acid concentration and sweat rate remains unclear.

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men.

What is the central question of this study? What are the effects of isomaltulose, an ingredient in carbohydrate-electrolyte beverages to maintain glycaemia and attenuate the risk of dehydration during exercise heat stress, on postexercise rehydration and physiological heat loss responses? What is the main finding and its importance? Consumption of a 6.5% isomaltulose-electrolyte beverage following exercise heat stress restored hydration following a 2h recovery as compared to a 2% solution or water only. While the 6.5% isomaltulose-electrolytes increased plasma volume and plasma osmolality, which are known to modulate postexercise heat loss, sweating and cutaneous vascular responses did not differ between conditions. Consequently, ingestion beverages containing 6.5% isomaltulose-electrolytes enhanced postexercise rehydration without affecting heat loss responses. Isomaltulose is a disaccharide carbohydrate widely used during exercise to maintain glycaemia and hydration. We investigated the effects of ingesting a beverage containing isomaltulose and electrolytes on postexercise hydration state and physiological heat loss responses. In a randomized, single-blind cross-over design, 10 young healthy men were hypohydrated by performing up to three 30min successive moderate-intensity (50% heart rate reserve) bouts of cycling, each separated by 10min, while wearing a water-perfusion suit heated to 45°C. The protocol continued until a 2% reduction in body mass was achieved. Thereafter, participants performed a final 15min moderate-intensity exercise bout followed by a 2h recovery. Following cessation of exercise, participants ingested a beverage consisting of (i) water only (Water), (ii) 2% isomaltulose (CHO-2%), or (iii) 6.5% isomaltulose (CHO-6.5%) equal to the volume of 2% body mass loss within the first 30min of the recovery. Changes in plasma volume (ΔPV) after fluid ingestion were greater for CHO-6.5% compared with CHO-2% (120min postexercise) and Water (90 and 120min) (all P≤0.040). Plasma osmolality remained elevated with CHO-6.5% compared with consumption of the other beverages at 30 and 90min postexercise (all P≤0.050). Urine output tended to be reduced with CHO-6.5% compared to other fluid conditions (main effect, P=0.069). Rectal and mean skin temperatures, chest sweat rate and cutaneous perfusion did not differ between conditions (all P>0.05). In conclusion, compared with CHO-2% and Water, consuming a beverage consisting of CHO-6.5% and electrolytes during recovery under heat stress enhances PV recovery without modulating physiological heat loss responses.

Effectiveness of a field-type liquid cooling vest for reducing heat strain while wearing protective clothing.

This study examined the effectiveness of a field-type liquid cooling vest (LCV) worn underneath an impermeable protective suit on heat strain during walking. Eight men walked for 60 min at a moderate speed (3.0 km/h) wearing the suit in a warm environment (33°C, 60% relative humidity) without (control, CON) or with the LCV. A smaller increase in rectal temperature was recorded in participants in the LCV than in the CON condition (37.6 ± 0.1°C vs. 37.9 ± 0.1°C, p<0.05). Walking while wearing the LCV reduced the level of physiological heat strain, as measured by the mean skin temperature (35.5 ± 0.1°C vs. 36.3 ± 0.1°C), chest sweat rate (13.5 ± 3.0 mg/cm2/h vs. 16.6 ± 3.8 mg/cm2/h), chest cutaneous vascular conductance (349 ± 88% vs. 463 ± 122%), body weight loss (0.72 ± 0.05% vs. 0.93 ± 0.06%), and heart rate (101 ± 6 beats/min vs. 111 ± 7 beats/min) (p<0.05, for all comparisons). These changes were accompanied by a decrease in thermal sensation and discomfort. These results suggest that a field-type LCV attenuates exertional heat strain while wearing impermeable protective clothing.

Activation of autonomic thermoeffectors preceding the decision to behaviourally thermoregulate in resting humans.

What is the central question of this study? Do increases in metabolic heat production and sweat rate precede the initiation of thermoregulatory behaviour in resting humans exposed to cool and warm environments? What is the main finding and its importance? Thermoregulatory behaviour at rest in cool and warm environments is preceded by changes in vasomotor tone in glabrous and non-glabrous skin, but not by acute increases in metabolic heat production or sweat rate. These findings suggest that sweating and shivering are not obligatory for thermal behaviour to be initiated in humans. We tested the hypothesis that acute increases in metabolic heat production and sweating precede the initiation of thermoregulatory behaviour in resting humans exposed to cool and warm environments. Twelve healthy young subjects passively moved between 17 and 40°C rooms when they felt 'too cool' (C→W) or 'too warm' (W→C). Skin and internal (intestinal) temperatures, metabolic heat production, local sweat rate (forearm and chest) and cutaneous vascular conductance (CVC; forearm and fingertip) were measured continually. Compared with pretest baseline (31.8±0.3°C), skin temperature was higher at C→W (32.0±0.7°C; P=0.01) and W→C (34.5±0.5°C; P<0.01). Internal temperature did not differ (P=0.12) between baseline (37.2±0.3°C), C→W (37.2±0.3°C) and W→C (37.0±0.3°C). Metabolic heat production was not different from baseline (40±9Wm-2 ) at C→W (39±7Wm-2 ; P=0.50). Forearm (0.06±0.01mgcm-2 min-1 ) and chest (0.04±0.02mgcm-2 min-1 ) sweat rate at W→C did not differ from baseline (forearm, 0.05±0.02mgcm-2 min-1 and chest, 0.04±0.02mgcm-2 min-1 ; P≥0.23). Forearm CVC was not different from baseline (0.30±0.21perfusion units (PU)mmHg-1 ) at C→W (0.24±0.11 PUmmHg-1 ; P=0.17), but was higher at W→C (0.65±0.33PUmmHg-1 ; P<0.01). Fingertip CVC was different from baseline (2.6±2.0PUmmHg-1 ) at C→W (0.70±0.42PUmmHg-1 ; P<0.01) and W→C (4.49±1.66PUmmHg-1 ; P<0.01). Thermoregulatory behaviour at rest in cool and warm environments is preceded by changes in vasomotor tone in glabrous and non-glabrous skin, but not by acute increases in metabolic heat production or sweat rate.

Underdiagnosis and undertreatment of asthma in children: a tertiary hospital's experience

Methods We studied 82 children (age 2-15y) that were referred to our clinic during 2013-2014 and their history and/or physical examination revealed a clinical suspicion of asthma, according to GINA. Children were evaluated by personal/ family history, physical examination, skin prick tests to common allergens, total/specific IgE levels. Lung function tests were carried out where possible. Chest X-ray and sweat test were performed if needed. Children were divided into three groups: children with asthma diagnosed for first time, children with asthma whose symptoms were uncontrolled and children with severe/persistent asthma.

Effects of micro-bubble bathing on thermoregulatory function, thermal comfort and skin cleansing

This study attempted to clarify how the presence of micro-bubbles, their particle diameter and density, and the circulation of water affect the thermoregulatory function, thermal comfort and skin cleansing of humans during hot water bathing. Nine healthy males (20.8 ± 0.5 years old) bathed for 10 min. During the experiment, we measured their tympanic temperature and leg skin temperature, forearm skin blood flow, chest sweat rate, leg heat flow as a thermoregulatory function index, saliva amylase, and subjective whole thermal sensation and comfort as a thermal comfort index, blood pressure and heart rate as a physiological index, and skin luminosity after putting evaluation smear on skin surface as a washing index. The bathing water was heated at of 40 °C and we examined four conditions: no micro-bubbles, a great quantity of bubbles released intermittently, a small quantity released continuously, and a small quantity released intermittently. We found that a small quantity of micro-bubbles in the bathing water had a greater thermal effect than water without micro-bubbles, because of the circulation of water. In contrast, we found that the use of micro-bubbles in great quantity had only a moderate thermal effect, but it gave rise to some inhibition of sympathetic activity. We think that this effect is caused by the circulation of water and to some air space formed on the skin surface. We also found that micro-bubbles enhance skin cleansing, especially in the condition of great quantity of bubbles and high circulation of water.

Effects of isotonic and isometric exercises with mist sauna bathing on cardiovascular, thermoregulatory, and metabolic functions

To clarify the effects of isometric and isotonic exercise during mist sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism, six healthy young men (22 ± 1 years old, height 173 ± 4 cm, weight 65.0 ± 5.0 kg) were exposed to a mist sauna for 10 min at a temperature of 40 °C, and relative humidity of 100 % while performing or not performing ∼30 W of isometric or isotonic exercise. The effect of the exercise was assessed by measuring tympanic temperature, heart rate, systolic and diastolic blood pressure, chest sweat rate, chest skin blood flow, and plasma catecholamine and cortisol, glucose, lactate, and free fatty acid levels. Repeated measures ANOVA showed no significant differences in blood pressure, skin blood flow, sweat rate, and total amount of sweating. Tympanic temperature increased more during isotonic exercise, and heart rate increase was more marked during isotonic exercise. The changes in lactate indicated that fatigue was not very great during isometric exercise. The glucose level indicated greater energy expenditure during isometric exercise. The free fatty acid and catecholamine levels indicated that isometric exercise did not result in very great energy expenditure and stress, respectively. The results for isotonic exercise of a decrease in lactate level and an increase in plasma free fatty acid level indicated that fatigue and energy expenditure were rather large while the perceived stress was comparatively low. We concluded that isotonic exercise may be a more desirable form of exercise during mist sauna bathing given the changes in glucose and free fatty acid levels.

투습방수의류의 착용쾌적성 평가

This study evaluates wear comforts of water-vapor-permeable (WVP) garments through a measurement of various parameters such as skin and rectal temperatures, microclimate between skin and clothing, sweat rate, and subjective sensations (thermal, wet and comfort sensations) to correlate the physiological responses of the human body with its comfort feeling. Wear comfort during a specific exercise on a treadmill in a climatic chamber (temperature T = <TEX>$20{\pm}0.5^{\circ}C$</TEX> and relative humidity H = <TEX>$50{\pm}10%$</TEX>) were studied using eight men wearing seven sportswear outfits (a long sleeve shirts and a long pants) made with seven different WVP fabrics. A comfort sensation was found to be highly correlated with skin T (p<.001), microclimate (T and H) between skin and clothing (p<.001) and sweat rate (p<.05). A regression model correlating comfort sensations and physiological responses obtained from wearer trials could be established: Y = 14.167 - 0.362 <TEX>${\times}$</TEX> X1 + 0.424 <TEX>${\times}$</TEX> X2 - 0.238 <TEX>${\times}$</TEX> X3 - 0.561 <TEX>${\times}$</TEX> X4 + 0.253 <TEX>${\times}$</TEX> X5 + 0.214 <TEX>${\times}$</TEX> X6 - 0.393 <TEX>${\times}$</TEX> X7 + 0.023 <TEX>${\times}$</TEX> X8 - 0.043 <TEX>${\times}$</TEX> X9. (Y = comfort sensation, X1 = forehead skin T, X2 = forearm skin T, X3 = hand skin T, X4 = thigh skin T, X5 = T of chest microclimate, X6 = T of thigh microclimate, X7 = chest sweat rate, X8 = H of back microclimate, X9 = H of thigh microclimate. The regression model obtained in this work can be used by manufacturers to objectively estimate the comfort sensation of sportswear before it is introduced to the consumer market. This study provides salient information to sportswear manufacturers and sportswear consumers.

Effects Of Acute Oral Glucose Or Fructose Ingestion On Thermoregulatory Responses During Passive Heating

BACKGROUND: It has been reported that acute hyperglycemia inhibits the rise in body core temperature and enhances cutaneous vasodilation during exercise in the heat. However, the effects of acute hyperglycemia on thermoregulatory responses to passive heating at rest remain unclear. Insulin is known to inhibit vasodilation by peripheral mechanisms and induce body core temperature rise by central mechanisms, therefore we further assessed the effects of insulin secretion to glucose ingestion by comparing the responses with fructose ingestion. PURPOSE: To test the hypotheses that hyperglycemia induced by oral glucose ingestion modifies thermoregulatory responses during passive heating at rest and that these responses are associated with insulin secretion. METHODS: Study 1: Eight healthy young men performed two trials. Subjects rested in a sitting position in an artificial climate chamber controlled at 28°C of Ta and 40% of RH during each trial. After 10 min baseline measurement, subjects drank glucose solution (GLU; water 300 ml + glucose 75 g) or water (CNT; water 300ml). Twenty min after drinking, subjects put their lower leg into hot water controlled at 42°C for 60 min. During the experiment, blood glucose concentration (BG), oxygen uptake (VO2), esophageal temperature (Tes), mean skin temperature (Tsk), heart rate (HR), blood pressure (BP), sweat rate (SR) and cutaneous vascular conductance (CVC) at chest and forearm, and total sweat rate (TSR) were measured. Study 2: Three healthy young men performed two trials. Subjects followed the same protocol as study 1, but drank glucose (GLU; water 300 ml + glucose 75 g) or fructose solution (FRU; water 300 ml + fructose 75g). RESULTS: Study 1: BG was significantly higher in GLU than CNT throughout heating. Forearm SR and TSR (GLU: 301 ± 28g, CNT: 328 ± 30g, mean ± SE, P < 0.05) were lower in GLU than CNT. Tes threshold for forearm sweating was relatively higher (P = 0.08) in GLU than CNT. Differnce in Tes threshold for forearm sweating (R = 0.96) and TSR (R = 0.78) between GLU and CNT were correlated with BG (both, P < 0.05). HR and systolic BP (both, P < 0.05) were higher in GLU than CNT, while there were no significant differences in VO2, Tes, Tsk, CVC at both sites, and chest SR between trials. Study 2: Tes, HR, and TSR (GLU: 340 ± 39 g, FRU: 441 ± 58 g, mean ± SE) were lower in GLU than FRU. CONCLUSIONS: Acute hyperglycemia induced by oral glucose ingestion inhibits sweating responses but has no effect on cutaneous vascular responses during passive heating at rest, which might be an effect of insulin secretion to glucose ingestion.

Protein and carbohydrate supplementation during 5-day aerobic training enhanced plasma volume expansion and thermoregulatory adaptation in young men

We examined whether protein and carbohydrate (CHO) supplementation during 5-day training enhanced plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in young men. Eighteen men [age 23 ± 4 (SD) yr] were divided into two groups according to supplements: placebo (CNT: 0.93 kcal/kg, 0.00 g protein/kg, n = 9) and protein and CHO (Pro-CHO: 3.6 kcal/kg, 0.36 protein/kg, n = 9). Subjects in both groups performed a cycling exercise at 70% peak oxygen consumption rate (VO2peak), 30 min/day, for 5 consecutive days at 30°C ambient temperature and 50% relative humidity and took either a placebo or Pro-CHO within 10 min after exercise for each day. Before and after training, PV at rest, heart rate (HR), and esophageal temperature (T(es)) during 30-min exercise at 65% of pretraining VO2peak in the same condition as training were determined. Also, the sensitivity of the chest sweat rate (ΔSR/ΔT(es)) and forearm vascular conductance (ΔFVC/ΔT(es)) in response to increased T(es) were determined. After training, PV and cardiac stroke volume (SV) at rest increased in both groups (P < 0.001) but the increases were twofold higher in Pro-CHO than CNT (P = 0.007 and P = 0.078, respectively). The increases in HR from 5 to 30 min and T(es) from 0 to 30 min of exercise were attenuated after training in both groups with greater attenuation in Pro-CHO than CNT (P = 0.002 and P = 0.072, respectively). ΔSR/ΔT(es) increased in CNT (P = 0.052) and Pro-CHO (P < 0.001) and the increases were higher in Pro-CHO than CNT (P = 0.018). ΔFVC/ΔT(es) increased in Pro-CHO (P < 0.001), whereas not in CNT (P = 0.16). Thus protein-CHO supplementation during 5-day training enhanced PV expansion and thermoregulatory adaptation and, thereby, the reduction in heat and cardiovascular strain in young men.

Impact of protein and carbohydrate supplementation on plasma volume expansion and thermoregulatory adaptation by aerobic training in older men

We examined whether protein-carbohydrate (CHO) supplementation immediately after exercise each day during aerobic training facilitated plasma volume (PV) expansion and thermoregulatory and cardiovascular adaptations in older men. Fourteen moderately active older men [68 +/- 5 (SD) yr] were divided into two groups so as to have no significant differences in anthropometric measures, PV, and peak oxygen consumption rate (Vo(2peak)). Each group was provided with a mixture of protein and CHO (3.2 kcal, 0.18 g protein/kg body wt, Pro-CHO, n = 7) or a non-protein and low-calorie placebo (0.5 kcal, 0 g protein/kg body wt, CNT, n = 7) immediately after cycling exercise (60-75% Vo(2peak), 60 min/day, 3 days/wk) each day for 8 wk at approximately 19 degrees C ambient temperature (T(a)) and approximately 43% relative humidity (RH). Before and after training, we measured PV, cardiac stroke volume (SV), and esophageal temperature (T(es)) during 20-min exercise at 60% of pretraining Vo(2peak) at 30 degrees C T(a) and 50% RH. Moreover, we determined the sensitivity of the chest sweat rate (DeltaSR/DeltaT(es)) and forearm vascular conductance (DeltaFVC/DeltaT(es)) in response to increased T(es) during exercise. After training, PV increased by approximately 6% in Pro-CHO (P < 0.001), with an approximately 10% increase in SV during exercise (P < 0.001), but not in CNT (P > 0.07). DeltaFVC/DeltaT(es) increased by 80% and DeltaSR/DeltaT(es) by 18% in Pro-CHO (both P < 0.01) but not in CNT (P > 0.07). Moreover, we found a significant interactive effect of group x training on PV, SV, and DeltaFVC/DeltaT(es) (all P < 0.02) but with no significant effect of group (P > 0.4), suggesting that the supplement enhanced these responses to aerobic training. Thus postexercise protein-CHO supplementation during training caused PV expansion and facilitated thermoregulatory and cardiovascular adaptations, possibly providing a new training regimen for older men.

Input–output relationships of a somatosympathetic reflex in human spinal injury

Spinal cord injury results in loss of supraspinal control of sympathetic outflow, yet preservation of spinal reflexes. Given the importance of reflex activation of sympathetic vasoconstrictor neurones to the generation of autonomic dysreflexia, we assessed the input-output relationship of the spinal somatosympathetic reflex induced by electrical activation of cutaneous afferents over the lower abdominal wall. In 13 spinal cord-injured subjects (C4-T10) we tested the hypothesis that the magnitude and duration of the vasoconstriction is directly related to the magnitude and duration of the stimulus train. Cutaneous vasoconstriction was measured with photoelectric plethysmography over a finger and toe; continuous blood pressure was recorded by radial artery tonometry, heart rate by ECG chest electrodes and sweat release by skin conductance. Four sets of trains of cutaneous electrical stimuli (20 Hz 1 s, 20 Hz 20 s, 20 Hz 1 s alternating on-and-off for 20 s and 1 Hz 20 s) were applied to the abdominal wall (10 mA) at 2-min intervals. Nine subjects showed vasoconstrictor responses to the stimulus trains. On average, both the magnitude and duration of the responses were similar irrespective of the type of stimulus train. We conclude that there is a non-linear relationship between somatic inputs and sympathetic vasoconstrictor outputs, and argue that a sustained vasoconstriction need not imply continuous sensory input to the spinal cord.

Effect of mist-sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism of exercising humans

To clarify the effect of isometric and isotonic exercise during mist-sauna bathing on the cardiovascular function, thermoregulatory function and metabolism, six healthy young men (22±1 years old, height 173±4 cm, weight 65.0±5.0 kg) were exposed to a mist-sauna for 10 min (room temperature 40 °C, relative humidity 100%) while resting or performing ∼30 W of isometric or isotonic exercises; the effects of the exercise were assessed by measuring tympanic temperature, heart rate, systolic blood pressure, chest sweat rate, chest skin blood flow, and plasma concentration of hormones (catecholamines and cortisol), glucose, lactate and free fatty acids.

Genomic and non-genomic effects of aldosterone on the individual variation of the sweat Na+ concentration during exercise in trained athletes

To clarify whether the resting background effects (genomic) or exercise-related action (non-genomic) of aldosterone (ALD) is primarily affected to an individual variation in the sweat Na+ concentration ([Na+]sweat), we analyzed the cross-sectional relationship between [Na+]sweat and the plasma ALD concentration during rest and exercise in a hot environment. Eleven college-aged male subjects with a mean maximal oxygen uptake of 48 (range 42-59) ml kg-1 min-1 performed three sessions of 20-min cycle exercise at two levels of intensity (40 or 60% VO2max) in a room maintained at 31 degrees C. The chest sweat rate (SRch) and its containing Na+ were higher and individual differences in SRch and [Na+]sweat were greater at 60% exercise than at 40% exercise. In each individual, the [Na+]sweat increased significantly (P<0.05) with the increase in the SRch. In all subjects, the mean [Na+]sweat during exercise correlated negatively with the resting plasma ALD level at either percentage, but it did not correlate with the exercising ALD. These results suggest that individual variations in the increase of the [Na+]sweat in response to a rise in the SRch may thus be more closely related to the resting ALD than to the exercising ALD. As a result, the genomic action of ALD may be affected more by the sweat Na+ variation than by the rapidly non-genomic action during exercise in humans.

Effects of alcohol on thermoregulation during mild heat exposure in humans

We investigated the effects of alcohol on thermoregulatory responses and thermal sensations during mild heat exposure in humans. Eight healthy men participated in this study. Experiments were conducted twice for each subject at a room temperature of 33°C. After a 30-min resting period, the subject drank either 15% alcohol (alcohol session) at a dose of 0.36 g/kg body weight or equal volume of water (control session). Skin blood flow and chest sweat rate in the alcohol session significantly increased over those in controls 10 min after drinking. Deep body temperature in the alcohol session started to decrease 20 min after the onset of sweating and eventually fell 0.3°C lower than in the controls. Whole body hot sensation transiently increased after alcohol drinking, whereas it changed little after water drinking. The increased “hot” sensation would presumably cause cool-seeking behavior, if permitted. Thus, alcohol influences thermoregulation so that body core temperature is lowered not only by automatic mechanisms (sweating and skin vasodilation) but also behaviorally. These results suggest that decreases in body temperature after alcohol drinking are not secondary to skin vasodilation, a well-known effect of alcohol, but rather result from a decrease in the regulated body temperature evidenced by the coordinated modulation of various effectors of thermoregulation and sensation.

Effects of CO 2-bath immersion (100 ppm) on thermoregulatory responses in humans

The effects of CO 2 (100 ppm) bathing were investigated. It was found that the chest blood flow, chest sweat rate and tympanic temperature were significantly greater during the immersion in CO 2 bathing than in freshwater bathing ( P < 0.05 ). Thus, CO 2 bathing at 100 ppm could produce cutaneous vasodilatation in the immersed skin, affecting thermoregulation.

Active recovery attenuates the fall in sweat rate but not cutaneous vascular conductance after supine exercise.

The purpose of this study was to identify whether baroreceptor unloading was responsible for less efficient heat loss responses (i.e., skin blood flow and sweat rate) previously reported during inactive compared with active recovery after upright cycle exercise (Carter R III, Wilson TE, Watenpaugh DE, Smith ML, and Crandall CG. J Appl Physiol 93: 1918-1929, 2002). Eight healthy adults performed two 15-min bouts of supine cycle exercise followed by inactive or active (no-load pedaling) supine recovery. Core temperature (T(core)), mean skin temperature (T(sk)), heart rate, mean arterial blood pressure (MAP), thoracic impedance, central venous pressure (n = 4), cutaneous vascular conductance (CVC; laser-Doppler flux/MAP expressed as percentage of maximal vasodilation), and sweat rate were measured throughout exercise and during 5 min of recovery. Exercise bouts were similar in power output, heart rate, T(core), and T(sk). Baroreceptor loading and thermal status were similar during trials because MAP (90 +/- 4, 88 +/- 4 mmHg), thoracic impedance (29 +/- 1, 28 +/- 2 Omega), central venous pressure (5 +/- 1, 4 +/- 1 mmHg), T(core) (37.5 +/- 0.1, 37.5 +/- 0.1 degrees C), and T(sk) (34.1 +/- 0.3, 34.2 +/- 0.2 degrees C) were not significantly different at 3 min of recovery between active and inactive recoveries, respectively; all P > 0.05. At 3 min of recovery, chest CVC was not significantly different between active (25 +/- 6% of maximum) and inactive (28 +/- 6% of maximum; P > 0.05) recovery. In contrast, at this time point, chest sweat rate was higher during active (0.45 +/- 0.16 mg.cm(-2).min(-1)) compared with inactive (0.34 +/- 0.19 mg.cm(-2).min(-1); P < 0.05) recovery. After exercise CVC and sweat rate are differentially controlled, with CVC being primarily influenced by baroreceptor loading status while sweat rate is influenced by other factors.

Relationship between aerobic power, blood volume, and thermoregulatory responses to exercise-heat stress.

To clarify the relationship between aerobic power (VO2max), blood volume (BV), and thermoregulatory responses to exercise-heat stress, we analyzed the cross-sectional relationship between the resting BV, plasma volume (PV), erythrocyte volume (EV), VO2max, forearm blood flow (FBF), and sweating responses during exercise in a hot environment (31 degrees C, 50% relative humidity). Twelve college-aged male subjects with a mean maximal oxygen uptake of 48 (range 42-59) mL.kg-1.min-1, a mean PV of 54 (range 42-72) mL.kg-1, a mean EV of 31 (range 23-43) mL.kg-1, and a mean BV of 85 (range 67-115) mL.kg-1 (measured by the Evans Blue dye dilution method) performed three sessions of 20-min cycle exercise at two levels of intensity (40% and 60% VO2max). The BV, PV and EV correlated positively with peak FBF (r = 0.596-0.711, P < 0.05), the increase of FBF in response to a unit rise in esophageal temperature (Tes; peak delta FBF/peak delta Tes) (r = 0.592-0.656, P < 0.05) and with total sweat loss (TSL) (r = 0.599-0.634, P < 0.05) during the exercise. The VO2max correlated with TSL during exercise at 40% VO2max (r = 0.578, P < 0.05), but not with peak FBF and peak delta FBF/peak delta Tes. The VO2max per lean body mass also showed a significant positive correlation with BV (r = 0.769, P < 0.01), PV (r = 0.706, P < 0.05), and with EV (r = 0.841, P < 0.001). The peak delta FBF/peak delta Tes was correlated positively with peak FBF (r = 0.597-0.830, P < 0.05-0.01) and negatively with peak Tes (r = 0.641-0.769, P < 0.05-0.01) during the exercise at the two levels. However, the chest sweat rate (CSR), TSL, and the increase of CSR in response to a unit rise in Tes (peak delta CSR/peak delta Tes) showed no correlation with peak Tes during the exercise at the two levels. These findings suggest that 1) heat dissipation responses during exercise were related more to blood volume than aerobic power and 2) skin blood flow was related more to body temperature than sweating responses during exercise under mild heat stress.