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PubMed1975

Sweating on paws and palms: what is its function?

Man sweats on his palms and the soles of his feet in response to stress and exercise, but not in response to heat. Several functions have been proposed for this type of sweating: increasing friction between skin and substrate; increasing the toughness of the skin; and increasing tactile sensitivity. This study uses a comparative approach to evaluate the role of footpad sweating on increasing friction, utilizing a variety of mammals which possess sweat glands on their footpads (rat, tenrec, hyrax, and dog). We found that all of these animals sweat on their paws while running. Blocking this sweating with atropine sulfate dramatically decreased the coefficient of static friction between the paw and the tread of an inclined treadmill. A similar dose of atropine sulfate had no effect on the coefficient of static friction in a rabbit, and animal that possesses no sweat glands on its paws. We conclude that an important function of this type of sweating is to help prevent slipping between the paw and sthe substrate during running or climbing, and we postulate that the sweating observed in response to stress may play an important role in preparing an animal for fleeing from stressful situations.

Animals↗

PubMed2003

Humid heat acclimation does not elicit a preferential sweat redistribution toward the limbs.

We tested the hypothesis that local sweat rates would not display a systematic postadaptation redistribution toward the limbs after humid heat acclimation. Eleven nonadapted males were acclimated over 3 wk (16 exposures), cycling 90 min/day, 6 days/wk (40 degrees C, 60% relative humidity), using the controlled-hyperthermia acclimation technique, in which work rate was modified to achieve and maintain a target core temperature (38.5 degrees C). Local sudomotor adaptation (forehead, chest, scapula, forearm, thigh) and onset thresholds were studied during constant work intensity heat stress tests (39.8 degrees C, 59.2% relative humidity) conducted on days 1, 8, and 22 of acclimation. The mean body temperature (Tb) at which sweating commenced (threshold) was reduced on days 8 and 22 (P < 0.05), and these displacements paralleled the resting thermoneutral Tb shift, such that the Tb change to elicit sweating remained constant from days 1 to 22. Whole body sweat rate increased significantly from 0.87 +/- 0.06 l/h on day 1 to 1.09 +/- 0.08 and 1.16 +/- 0.11 l/h on days 8 and 22, respectively. However, not all skin regions exhibited equivalent relative sweat rate elevations from day 1 to day 22. The relative increase in forearm sweat rate (117 +/- 31%) exceeded that at the forehead (47 +/- 18%; P < 0.05) and thigh (42 +/- 16%; P < 0.05), while the chest sweat rate elevation (106 +/- 29%) also exceeded the thigh (P < 0.05). Two unique postacclimation observations arose from this project. First, reduced sweat thresholds appeared to be primarily related to a lower resting Tb, and more dependent on Tb change. Second, our data did not support the hypothesis of a generalized and preferential trunk-to-limb sweat redistribution after heat acclimation.

Acclimatization↗

PubMed1986

Influence of beta-adrenergic blockade on the control of sweating in humans.

To evaluate the role of beta-adrenergic receptors in the control of human sweating, we studied six subjects during 40 min of cycle-ergometer exercise (60% maximal O2 consumption) at 22 degrees C 2 h after oral administration of placebo or nonselective beta-blockade (BB, 80 mg propranolol). Internal temperature (esophageal temperature, Tes), mean skin temperature (Tsk), local chest temperature (Tch), and local chest sweat rate (msw) were continuously recorded. The control of sweating was best described by the slope of the linear relationship between msw and Tes and the threshold Tes for the onset of sweating. The slope of the msw-Tes relationship decreased 27% (P less than 0.01), from 1.80 to 1.30 mg X cm-2 X min-1 X degree C-1 during BB. The Tes threshold for sweating (36.8 degrees C) was not altered as the result of BB. These data suggest that BB modified the control of sweating via some peripheral interaction. Since Tsk was significantly (P less than 0.05) reduced during BB exercise, from a control value of 32.8 to 32.2 degrees C, we evaluated the influence of the reduction in local skin temperature (Tsk) in the altered control of sweating. Reductions in Tch accounted for only 45% of the decrease in the slope of the msw-Tes relationship during BB. Since evaporative heat loss requirement during exercise with BB, as estimated from the energy balance equation, was also reduced 18%, compared with control exercise, we concluded that during BB the reduction in sweating at any Tes is the consequence of both a decrease in local Tsk and a direct effect on sweat gland.

Adult↗

PubMedDate not supplied

Associations between night sweats and other sleep disturbances: An OKPRN study.

PURPOSE: Surprisingly little is known about the causes and implications of night sweats. This study was designed to clarify further the associations between night sweats and sleep-related symptoms. METHODS: We undertook a cross-sectional study of consecutive adult patients seen in 10 primary care physicians' offices. Data were collected and transmitted by a personal digital assistant. Information included demographic variables; height, weight, and blood pressure; occurrence of a variety of sleep-related symptoms; and occurrence and severity of night sweats, day sweats, and hot flashes in the past month. For women, information about menstrual status was also obtained. RESULTS: Thirty-four percent of the 363 patients interviewed reported night sweats, one half of whom reported saturating their bedclothes. In the multivariate model, night sweats were associated with daytime tiredness (OR = 1.99; 95% CI, 1.12-3.53), waking up with a bitter taste in the mouth (OR = 1.94; 95% CI, 1.19-3.18), legs jerking during sleep (OR = 1.78; 95% CI, 1.05-3.00), and awakening with pain in the night (OR = 1.87; 95% CI, 1.16-2.99). CONCLUSIONS: Night sweats are associated with several sleep symptoms. Both night sweats and sleep disturbances are commonly experienced by adult primary care patients. When their patients report night sweats, clinicians should consider asking about sleep quality and sleep-related symptoms.

Adolescent↗

PubMed1987

Physiological factors associated with the onset of sweating.

The influence of esophageal (Tes) and skin temperature (Tsk) variations, body heat storage, and individual parameters on the initiation of sweating was investigated in 9 unacclimated subjects during thermal transients induced by exercise (25, 50, or 75 W) and by a step change in ambient temperature from 28 degrees C to 23, 28, 36.5, 45, or 50 degrees C. Seventy-four onsets of sweating were observed during the exposures, the sweating delay averaging 3 min at 45 and 50 degrees C, 6 min at 36.5 degrees C, and 9.5 min at 28 degrees C. In warm conditions (36.5 to 50 degrees C), the onset of sweating could mainly be related both to the level of Tsk and its rate component, whereas in cooler conditions (28 and 23 degrees C), the onset of sweating could only be related to a positive rate of Tes variation, the Tsk level being low and steady. On the whole set of data, the Tes changes at the onset were inversely related to the Tsk changes. The cumulated heat storage at the onset of sweating was 37 kJ/m2 (S.D. 25). It varied not only among subjects (range: 11-66 kJ/m2) but also within subjects even when differences in thermal state prior to exercise were accounted for. Among the individual parameters investigated, the magnitude of the decrease in Tes observed in response to the start of exercise was found to have a significant effect on the sweating delay. The Tes decrease was inversely related to the subject's skinfold thickness, and in a given subject, inversely related to the preexercise Tsk. It is concluded that the results are in agreement with a summation model of internal and mean skin temperatures on the sweating drive but that they do not verify the hypothesis of a critical level of heat storage at the onset of sweating.

Body Temperature↗

PubMed1976

[Influence of hydrothermal ambient conditions on sweat evaporation efficiency].

Sweat efficiency is defined as the ratio between evaporative and sweat rates. The work was carried out on two resting subjects acclimatised to humid heat. Body sweat rate and rate of sweat loss by dripping were recorded separately by continuous weighing. Evaporation from the skin was obtained by the difference between the two weight loss curves. The subjects were exposed for 75 minutes to increases in humidity levels as constant air temperatures (42, 44, 46, or 48 degrees C). The amplitude of the increases was successively equal to 7.5, 15.0, 22.5 or 50.0 mb of water vapor pressure. During the 75 minutes preceding each increase the water vapor pressure of the air was maintained at 20.0 mb. 1. Sweat efficiency decreases prior to complete wetting of the skin surface. The inter-individual mean value of the wetted skin area threshold over which sweat efficiency is less than 1 is around 60%. 2. Sweat efficiency is linearly related to the reciprocal of the required wetted skin area (see article). These results are compared with those of other authors. The differences observed are explained in terms of physiological or physical variables involved in the sweat rate control or in the evaporative sweat loss. These include wetness of skin, posture, activity of subjects and the velocity of air over the skin surface.

Adult↗

PubMed1992

[Effect of thermal dehydration on blood levels of volume- regulating hormones and sweat electrolytes in patients with essential hypertension treated with propranolol].

The present study aims to answer the following questions: 1. do secretion of volume related hormones in patients with EH pre- and post treatment with propranolol differ from normotensive subjects if examined in thermal dehydration conditions; 2. is the electrolyte composition of thermal sweat related to the plasma profile of volume related hormones? and 3. does treatment by propranolol influence sweat electrolytes in EH patients. In 15 patients with EH and in 20 healthy subjects a thermal dehydration test was performed. In patients with EH this test was done twice: before treatment and after 6 weeks of propranolol therapy. In all subjects the plasma renin activity (PRA), aldosterone (Ald), AVP and ANP were measured before and after thermal dehydration. In sweat samples collected after 15' and 45' of thermal dehydration (the concentration of Na, K and Cl was assessed). In hypertensive patients before propranolol treatment significantly higher values of PRA, Ald and ANP were found, while sweat concentrations of Na and Cl were significantly lower than in controls. After propranolol treatment sweat electrolytes concentrations showed a tendency to normalize. No significant correlation was found between the plasma hormonal profile and sweat Na, K and Cl concentrations respectively both in controls and patients with EH pretreatment. A significant positive correlation was noticed only in hypertensive patients posttreatment between ANP and sweat potassium concentration respectively, and significant negative correlation between PRA and sweat sodium and chloride concentration. From results obtained in this paper it seemed, that volume related hormones (Ald, AVP, ANP) do not seem to influence markedly the electrolyte composition of thermal sweat both in healthy subjects and in hypertensive patients.

Adult↗

PubMed1992

Sweat electrolyte loss during exercise in the heat: effects of gender and maturation.

Humans may lose large amounts of water and electrolytes from sweat during prolonged exercise in a hot climate. Gender and maturational differences for the total sweat electrolyte losses have not been reported. The purpose of this study was to compare sweat electrolyte losses of prepubescent (PP), pubescent (P) and young adult (YA) males and females, under the same environmental conditions and relative exercise intensities. Twenty-five females (8 PP, 9 P, 8 YA) and 26 males (10 PP, 8 P, 8 YA) cycled for two 20-min bouts at 50% of their peak VO2 in a climatic chamber (42 degrees C, 18% relative humidity). Sweat was collected from a plastic bag attached to the lower back. Total body sweat loss was calculated from the differences in nude body weight corrected for fluid intake, urine, and respiratory water loss. Sweat [Na+] and [Cl-] tended to increase with maturation while sweat [K+] was lower in YA compared with that of PP. Children had a lower sweating rate than YA, even when corrected for body surface area. As a result, total Na+ and Cl- losses per kg body weight from sweat (mEq.kg-1.h-1) were higher in YA compared with those of PP and P; however, no maturational difference was found in K+ losses. Within the same maturational group, there were no gender differences in any of the electrolyte losses. These results may be useful in recommending "optimal" fluid-electrolyte drinks for children exercising in the heat.

Adolescent↗

PubMed1991

[Local effect of calcitonin gene-related peptide on human sweat gland function].

The effect of local administration of calcitonin gene-related peptide (CGRP) on sweating activity was evaluated on normal human volunteers. CGRP and methacholine chloride (MCH) was dissolved in 0.1 ml of 0.9% NaCl solution to a specified concentration, and was injected intradermally at the center of a 1.3 cm2 forearm test area. The sweat rate was recorded continuously by capacitance hygrometry in a relatively cool environment (Ta, 23 degrees C). CGRP did not elicit any sweat secretion when administrated by alone, but significantly increased the sweat rate when it was administrated with MCH. The maximum enhancement of MCH-induced sweating by CGRP was observed at a concentration of 10(-5) g/ml of CGRP. There was clear dose-dependent relationship between the dose of CGRP and its enhancement. Recently, CGRP-like immunoreactivity is demonstrated to be present in cholinergic nerve terminals around the human sweat glands. These observations have strongly suggested that CGRP enhances the cholinergic sweating activity. Although the underlying mechanism is still obscure, CGRP may enhance the sweating as a consequence of vasodilation which has been known to be a major activity of CGRP. As for the evaluation of human sweat gland function, CGRP-induced peptidergic regulation should be considered as well as cholinergic regulation.

Acetylcholine↗

PubMedDate not supplied

Importance of dynamics of sweating in men during exercise.

Influence of dynamics of sweating on rectal temperature increase was tested in 3 groups of men performing cycle exercise with intensity of 65, 90 and 120 W, respectively, in 22 degrees C chamber temperature and 30% of relative air humidity. During exercise at 65 and 90 W the subjects wore suits while exercising with intensity of 120 W they wore only shorts. The dynamics of sweating was described by delay in onset of sweating and time constant of the reaction. Wearing caused significant increase in skin humidity and decreased evaporative rate of sweating. Sweat rate during steady state was related to the metabolic rate in naked (r = 0.89, p less than 0.002) as well as in wearing subjects (r = 0.93, p less than 0.01). Delay in onset of sweating was, in average, 5 min with a time constant of 7 min. Both factors showed a tendency to be shorter with increasing work intensity. Mean increase in rectal temperature was proportional to the intensity of exercise although the individual delta Tre correlated well with the dynamics of sweating in naked (r = 0.83, p less than 0.01) and wearing subjects (r = 0.84, p less than 0.01). Since delta Tre was smaller in subjects with shorter inertia time of sweating in response to beginning of exercise at the same intensity it is concluded that the dynamics of sweating can play an important role in limiting body temperature increase in working men.

Adolescent↗

PubMed1985

[Sweating response to abrupt changes in work load].

Changes in sweat rate on the palm and on the general body surface in response to stepwise increases and decreases in work load during exercise on a bicycle ergometer were examined in relation to body temperature and heart rate in six male subjects (three trained and three untrained), in an attempt to evaluate thermal and nonthermal factors responsible for those changes. In all the untrained subjects, a transient, marked increase in palmar sweat rate was observed upon an abrupt increase (and occasionally upon an abrupt decrease) in work, while an increase in sweat rate on the general body surface was also rapid and marked. On the other hand, in all the trained subjects, palmar sweat rate was low and hardly showed a substantial increase in response to an abrupt increase in work load, to which sweating on the general body surface responded slowly by a gradual increase. While sweat rate on the general body surface showed a significant correlation with esophageal temperature and with heart rate, palmar sweat rate was not correlated with esophageal temperature but was significantly correlated with heart rate. Moreover, repeated increases and decreases in work load often led to progressive weakening of palmar sweating due apparently to the development of habituation. The present results suggest that responses of sweating to stepwise changes in work load are not solely dependent upon the thermoregulatory mechanism but are affected considerably by increase and decrease in psychic excitement and/or those in discharges of the sympathetic nervous system accompanying changes in work load.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Sweat electrolytes in patients with advanced renal failure.

The sweat gland has some similarity with the convoluted tubules of the kidney. Little is known about sweat secretion and electrolyte content of sweat in the uremic gland. A pilocarpine ionotophoresis sweat test was performed in 40 patients with advanced renal failure (RF). Sweat secretion was measured and analyzed for Na, K, and Cl and correlated to blood parameters, type, and duration of dialysis. The sweat weight was significantly lower in all RF patients when compared with this parameter in healthy controls (p < 0.0001). No difference was noted between patients undergoing hemodialysis, those undergoing continuous ambulatory peritoneal dialysis, and those not undergoing dialysis. Men sweated more than women among RF patients and among controls (p < 0.0001). An inverse correlation was found between sweat weight and blood calcium levels (p < 0.001). Sweat K concentration was significantly higher (p < 0.0001) in patients with RF than in healthy controls, while the concentrations of Na and Cl were similar. Several mechanisms are suggested as possible explanations for these changes.

Aged↗

PubMed1998

Flight coverall microclimate evaluation using a Japanese type sweating mannequin.

BACKGROUND: It is important to examine the microclimate of a pilot's clothing to evaluate the heat stress the clothing imparts on a pilot, but problems arise with regard to individual variation (phenotype of the pilot, sweating dose, wear condition of the flight coveralls, etc.). HYPOTHESIS: The present study used a Japanese type sweating mannequin (TOM-III) to evaluate the microclimate of flight coveralls. METHODS: TOM-III (TOYOBO, Co., Ltd., Tokyo, Japan) has a characteristic Japanese human body type, and the sweat rate and body temperature can be regulated (240 g of sweat per hour, 36.0 degrees C). The microclimate of the clothing was evaluated by means of 20 temperature/humidity sensors located on the surface of the mannequin skin. TOM-III wore four different assemblies of clothing (CWU-66/P USAF chemical defense flight coverall; JASDF summer-type flight coverall which is similar to the nonchemical defense USAF flight coverall; ordinary 100% cotton underwear; and CWU-66/ P with cotton underwear). We put TOM-III in climatic chamber (21.2 +/- 0.5 degrees C, 50.0 +/- 3.0% relative humidity (RH), 0.1 m air flow x s(-1), dressed in test clothing, and measured the inside temperature (IT) and inside relative humidity (IRH) of the clothing for 60 min (10 min non-sweating, 30 min sweating and 20 min non-sweating). RESULTS: Approximately 5 min after the onset of sweating, the IRH of the CWU-66/P (38.0%) was lower than JASDF flight coverall (42.1%; p < 0.01). At the end of the sweating period, the IRH of the CWU-66/P and the JASDF flight coverall were 46.2% and 52.6%, respectively (p < 0.01). The results indicated that the CWU-66/P flight coverall was better suited for heat stress than the JASDF summer-type flight coverall. CONCLUSIONS: TOM-III may be useful for microclimate evaluation and/or the development of clothing without considering individual variation against various climatic conditions.

Aerospace Medicine↗

PubMedDate not supplied

Anatomy of the sweat glands, pharmacology of botulinum toxin, and distinctive syndromes associated with hyperhidrosis.

For a long period the therapeutic modalities to treat focal hyperhidrosis (HH) were very limited. Due to this the problem of focal HH was delt with stepmotherly. Nowadays we can consider BTX as the therapy of choice for axillary HH after topical treatment with aluminium salts have failed. The amount of successful reports on botulinum toxin (BTX) in the treatment of focal HH brought a change and the interest for this specific disorder grew. This article gives details on anatomy and physiology of sweating and mechanism of BTX. Further distinctive syndromes associated with HH, which all can be treated with BTX like localized unilateral hyperhidrosis (LUH), Ross' Syndrome and Frey' Syndrome are presented. A diagnosis of primary HH is usually based on the patients's history, typical younger age and visible signs of excessive sweating. Before treatment it is important to objectify focal HH with performing sweat tests such like Minor starch test and/or gravimetry. The total number of sweat glands is somewhere between 2 and 4 million and only about 5% are active at the same time, indicating the enormous potential for sweat production. The eccrine sweat gland is a long-branched tubular structure with highly coiled secretory portion and a straight ductular portion. Sweat is produced by clear and dark cells and is a clear hypotonic, odorless fluid. In response to nerve impulses, Acetylcholine (ACh) is released from the presynaptic nerve endings and then binds to postsynaptic cholinergic receptors presumably present in the basolateral membrane of the clear cells. This activates a complex in- and efflux of electrolytes creating the hypotonic sweat. Injection of BTX leads to temporary chemodenervation with the loss or reduction of activity of the target organ. BTX is consisted of a heavy and a light chain. The structural architecture of BTX comprises three domains-L, H(N) and H(C)-each with a specific function in the mechanism of cell intoxication. The heavy chain is responsible for binding to the nerve cell, whereas the light chain catalyzes the proteolysis of one of the three SNARE proteins (Snap-25, Vamp or Syntaxin) depending to the serotype of BTX (7 serotypes A-G). Once cleaved by BTX, the SNARE proteins cannot become part of the complex capable of mediating the vesicle membrane fusion and therefore prevents the release of ACh and hence transmission of the nerve impulse.

Axilla↗

PubMedDate not supplied

Determinants of hot flashes and night sweats.

PRIMARY OBJECTIVE: The purpose of this study was to identify determinants of hot flashes and night sweats, two vasomotor symptoms associated with the hormonal changes of the menopause transition. METHODS: Participants were 293 women, aged 45 to 55, randomly selected from automated demographic and membership records of a health maintenance organization in the northeast USA. Letters were mailed to eligible women, followed by face-to-face interviews. RESULTS: Hot flashes during the month before interview were reported by 57% of the participants, although only 9% of the entire sample reported hot flashes to be "bothersome". Night sweats were reported by 36% of all participants, with 6% reporting night sweats to be "bothersome". Fifty-four percent of women reporting hot flashes also reported night sweats. In logistic regression analyses that controlled for menopause status and use of hormone therapy (HT), daily alcohol consumption significantly increased the risk of hot flashes, night sweats, and bothersome night sweats. Higher education and an excellent self-rating of health decreased the risk of night sweats, but not hot flashes. Smoking increased the risk of bothersome hot flashes, but not bothersome night sweats. CONCLUSIONS: In logistic regression analyses, alcohol consumption was a significant predictor of vasomotor symptoms. A slightly different set of variables were associated with hot flashes compared to night sweats.

Alcohol Drinking↗

PubMed1995

Ultrastructural localization of alkaline phosphatase activity in human eccrine and apocrine sweat glands.

Alkaline phosphatase (ALP) is a membrane-bound enzyme that catalyzes the hydrolysis of inorganic and organic monophosphate esters at alkaline pH. Although the functions of ALP are poorly understood, it is believed to be involved in membrane transport. Because little is known about the functions and distribution of ALP in the sweat glands, we studied the localization of ALP in human sweat glands with light and electron microscopic enzyme cytochemistry. In eccrine sweat glands, ALP was restricted to the cell membranes of intercellular canaliculi. Luminal cell membranes of secretory cells that are in continuity with intercellular canaliculi did not show ALP activity. These results suggest that ALP participates in the production of primary sweat at intercellular canaliculi. In apocrine sweat glands, basal cell membranes of secretory cells and myoepithelial cell membranes that were in apposition with each other showed ALP activity, where as no activity was seen in eccrine sweat glands. These differences in the distribution of ALP in myoepithelial cells between eccrine and apocrine sweat glands might be related to the functional differences of these sweat glands. ALP histochemistry could help to diagnose and to determine the direction of differentiation in sweat gland tumors.

Alkaline Phosphatase↗

PubMed1991

A simple and disposable sweat collector.

Apart from in cystic fibrosis, where sweat analysis provides valuable diagnostic information, sweat yields remain an overlooked biological fluid. Technical problems (dilution, condensation, contamination, evaporation, etc.) linked to currently available collection procedures are of concern and thwart their use. To overcome some of these technical difficulties, an original sweat-collection technique is described. A collection capsule is created inside a flexible, adhesive and disposable anchoring membrane pasted onto the skin. A fluid-tight window is positioned in the upper part of the pocket and gives access to its content. Through the collection window, complete emptying of the sweat collector can be achieved repeatedly by suction using a vacutainer tube inserted in a tube holder equipped with a long dull needle. With prior addition of a suitable marker, fractional samplings can also be performed using a precision micropipette. This collecting method allows for kinetic studies on sweat rate and sweat content. The limited bias-inducing manipulations linked to the described technique, coupled with the ease of performing kinetic studies on sweat volume and content, make this original tool a reliable and accurate sweat-collection technique.

Adolescent↗

PubMed1999

Mechanisms underlying the age-related decrement in the human sweating response.

To examine the mechanisms underlying the age-related decrement in the ability to sweat, seven older (64-76 years) and seven younger (20-24 years) men participated in a 60-min sweating test. The test consisted of placing the subject's lower legs in a water bath at 42 degrees C while sitting in a controlled environment of 35 degrees C ambient temperature and 45% relative humidity. The rectal (Trc) and skin temperatures, local sweating rates (m(sw): on the forehead, chest, back, forearm and thigh) and the frequency of sweat expulsion (f(sw)) were measured during the test. No group difference was observed in the mean body temperature (Tb) throughout the passive heating, although the older men had a higher Tre and a lower mean skin temperature during the last half of the 60-min test. There were no group differences in the Tb threshold for sweating, although the time to the onset of sweating tended to be longer for the older men regardless of body site. The m(sw) increased gradually for approximately 35 min after the start of heat exposure in the older men and for 30 min in the younger men and then reached a steady state. During the first half of the test, the older men had a significantly lower m(sw) at all sites. During the last half of the test, only m(sw) on the thigh was significantly lower in the older men than in the younger men. There was no group difference in the slope of f(sw) versus Tb (an indicator of the change in the central sudomotor response to thermal input). The slope of m(sw) versus f(sw) (an indicator of the change in peripheral activity in response to central sudomotor changes) was significantly lower on the thigh in the older men, but there were no differences for the other sites. These results suggest that in older men the lower thigh m(sw) observed during the last half of the heat test was possibly due to age-related modifications of peripheral mechanisms involving the sweat glands and surrounding tissues. It was not due to a change in the central drive to sudomotor function. Furthermore, the sluggish m(sw) responses in the older men appear to have been related to age-related modifications of the sensitivity of thermoreceptors in various body regions to thermal stimuli. They may also involve lower sweat glands' sensitivity to cholinergic stimulus or sluggish vasodilatation, and do not reflect age-related changes in the central drive.

Adult↗