Sweat secretion from the torso during passively-induced and exercise-related hyperthermia

Abstract

Thermal sweating from the human torso accounts for about half of the whole-body sweat secretion, yet its intra-segmental distribution has not been thoroughly examined. Therefore, the aim of the current study was to provide a detailed description of the distribution of eccrine sweating within the torso during passively-induced (water-perfusion garment: 40 degrees C) and progressively increasing, exercise-related thermal strain (36 degrees C, 60% relative humidity). Sudomotor function was measured in ten males using ventilated sweat capsules (3.16 cm(2)) attached to twelve sites on the ventral (four), lateral (three) and dorsal (four) torso, and upper shoulder surfaces. Sweating increased asymptotically in all sites, with the final core temperature averaging 39.7 degrees C (+/-0.1) and heart rates being 181 b min(-1) (+/-2). During exercise, the mean torso sweat rate averaged 1.35 mgcm(-2)min(-1), with sweating from the lateral torso surfaces generally being the lowest. Each of the between-site comparisons with the lateral torso differed significantly (P < 0.05), except for comparisons with the chest (P = 0.051) and shoulder (P > 0.05). The intra-segmental differences between the lateral torso and the chest, abdomen, upper- and lower-back areas were significantly accentuated during exercise. From these data, it is evident that the torso is another region that does not have a uniform distribution of thermally-induced sweating. Thus, it is no longer acceptable for researchers, modellers, sweating manikins engineers or clothing manufacturers to assume that the sweat rates for all local sites within any body segment are equivalent.

Body mapping of sweating patterns in male athletes in mild exercise-induced hyperthermia

“…No significant differences in the T sk or changes in sweat ratio distribution between the anterior and posterior torso were observed between any of the conditions. This is consistent with current literature since higher RSR on the posterior compared to anterior torso have been observed both with (Havenith et al 2008a) and without the presence of wind (Machado-Moreira et al 2008b). Overall, regarding the influence of local T sk , it is concluded that when substantially changing it locally a clear effect is present (Nadel et al 1971a), but when looking at the natural variation over the body, as done here, this effect is of minor importance.…”

“…In contrast to the present data, Weiner (1945) found lower sweat rates on the posterior compared to anterior torso, however, the small sample size (n=3) may have been inadequate given the high variation in sweating between individuals. A medial to lateral decrease in sweat rate was observed across the torso in the present study and was similarly noted by Machado-Moreira et al (2008b) and Havenith et al (2008b), but not by Cotter et al (1995). Hertzman (1957) and Weiner (1945) similarly found lower sweat rates along the axillary line, supporting the present data.…”

Improved Procedure for Estimating Time-dependent Changes in Local Sweat Rates by Measuring Local Sweat Volumes

“…The ventilated capsule (7.1 cm 2 ) was fixed to the upper section of the left scapula and the local sweat rate (LSR vc ) was measured during the exercise by using the ventilated capsule method [3][4][5][6][7][10][11][12][13]15,16] After the exercises, a part of the absorbent pad was pulled out from each of the tailored pads fixed on the skin. Each absorbent pad was quickly placed, separately, into an impermeable plastic Ziploc bag and weighed with the bag.…”

“…Previous studies of regional sweat rates found that the local sweat rate (LSR) clearly varies among the different body sites [1][2][3][4][5][6], and that LSR on the forehead and torso was greater than that of the limbs [1][2][3][4]. Some studies have focused on the differences in sweat regulation depending on maturation and aging [7][8][9][10][11], sex [12,13], fitness [8,14,15], and heat acclimation [8,16] to elucidate the mechanism underlying thermoregulation.…”

“…Some studies have focused on the differences in sweat regulation depending on maturation and aging [7][8][9][10][11], sex [12,13], fitness [8,14,15], and heat acclimation [8,16] to elucidate the mechanism underlying thermoregulation. LSR is measured by using a ventilated capsule, and is estimated from the difference in vapor content between the influx and efflux air moving through the capsule at a known flow rate [3][4][5][6][7][10][11][12][13]15,16]. A few small capsules with less than 10 cm 2 in the project areas were generally used, with one capsule per one body part in the majority of previous studies.…”