Depressed sweating during exercise at altitude

Medicine & Science in Sports & Exercise, 2002

This study aimed to assess the effect of acute exposure to moderate altitude on kinematic variables of the ippon-seoi-nage and on the mechanical outputs of the countermovement jump (CMJ). Thirteen elite male judokas from the Spanish Judo Training Centre in Valencia (age: 21.54 ± 2.15 years) participated in the study. All of them performed an incremental CMJ test and an ippon-seoi-nage technique test before (N) and after the ascent to a moderate altitude of 2320 m above the sea level (H). A linear velocity transducer was attached to the bar to assess the mechanical outputs of each loaded CMJ at different percentages of their own body weight (25, 50, 75 and 100%). A wearable sensor was used to assess the kinematic variables (times, accelerations and angular velocities) transferred to a dummy during the technique test. The kinematic variables showed great individual reliability (CV = 8.46% in N; CV = 8.37% in H), which contrasted with low reliability observed when the whole group was considered. The smallest important CV ratio (>1.15) showed that H caused changes in the reliability of the kinematic variables, with some variables becoming more reliable and others losing the reliability they had in N. H also caused small increments in peak velocity across all loads tested in the CMJ (+3.67%; P<0.05). In contrast, no changes in the kinematic variables were verified. In addition, there was no association between leg extension capability and the acceleration (r =-0.16 ± 0.19 in N; r =-0.24 ± 0.19 in H) or angular velocity (r =-0.19 ± 0.24 in N; r =-0.30 ± 0.26 in H) of the ippon-seoi-nage, nor was acute exposure to H found to affect this association (P>0.05). Differences between individual and within-groups CV confirm the individual adaptations that each judoka makes during this technique. Additionally, the CV ratio shows a change in the space-time pattern of the technique in H. Therefore, it would be necessary to include an adaptation period to adapt the technique after the ascent in altitude. Further studies are needed to confirm the relationship and transference from the velocity gains in CMJ during altitude training.

The American journal of physiology

Journal of Thermal Biology, 2005

The aim of the present study was to test the hypothesis that the sweating during graded exercise until exhaustion in a temperate environment would be greater after heat acclimation. Six healthy young males performed an exercise-heat stress acclimation protocol during 9 days. Before (PRE) and after (POS) the acclimation protocol they performed a graded exercise until exhaustion and the sweat loss during exercise increased after acclimation (3.9471.10, PRE, and 4.8671.70 g m À2 min À1 , POS; po0.05). The results showed that daily prolonged exposures to exercise-heat stress increased sweating during a graded and short duration exercise in a temperate environment. r

European Journal of Applied Physiology, 1997

We demonstrated previously that esophageal temperature (T es ) remains elevated by »0.5°C for at least 65 min after intense exercise. Following exercise, average skin temperature (T avg ) and skin blood¯ow returned rapidly to pre-exercise values even though T es remained elevated, indicating that the T es threshold for vasodilation is elevated during this period. The present study evaluates the hypothesis that the threshold for sweating is also increased following intense exercise. Four males and three females were immersed in water (water temperature, T w = 42°C) until onset of sweating (Immersion 1), followed by recovery in air (air temperature, T a = 24°C). At a T a of 24°C, 15 min of cycle ergometry (70% VO 2max ) (Exercise) was then followed by 30 min of recovery. Subjects were then immersed again (T w = 42°C) until onset of sweating (Immersion 2). Baseline T es and T skavg were 37.0 (0.1)°C and 32.3 (0.3)°C, respectively. Because the T skavg at the onset of sweating was dierent during Exercise [30.9 (0.3)°C] than during Immersion 1 and Immersion 2 [36.8 (0.2)°C and 36.4 (0.2)°C, respectively] a corrected core temperature, T es (calculated), was calculated at a single designated skin temperature, T sk(designated) , as follows:

Journal of Applied Physiology, 2000

To investigate how the sweating response to a sustained handgrip exercise depends on changes in the exercise intensity, the sweating response to exercise was measured in eight healthy male subjects. Each subject lay in the supine position in a climatic chamber (35°C and 50% relative humidity) for ∼60 min. This exposure caused sudomotor activation by increasing skin temperature without a marked change in internal temperature. After this period, each subject performed isometric handgrip exercise [15, 30, 45, and 60% maximal voluntary contraction (MVC)] for 60 s. Although esophageal and mean skin temperatures did not change with a rise in exercise intensity and were similar at all exercise intensities, the sweating rate (SR) on the forearm increased significantly ( P &lt; 0.05) from baseline (0.094 ± 0.021 mg ⋅ cm−2 ⋅ min−1at 30% MVC, 0.102 ± 0.022 mg ⋅ cm−2 ⋅ min−1at 45% MVC, 0.059 ± 0.009 mg ⋅ cm−2 ⋅ min−1at 60% MVC) in parallel with exercise intensity above exercise intensity at 30%...

MHSalud: Revista en Ciencias del Movimiento Humano y Salud

The purpose of this study was to explore the influence of altitude and environmental temperature on muscle mechanical and functional activation after 30&#39; Time Trial run (30&#39; TT). Twenty physical active males (Age= 20.4 ±3.21 years, VO2max= 47.2 ±5.2 ml/kg/min) performed a 30&#39; TT in three different conditions of altitude and temperature: Control Condition [CC] (1137 m.a.s.l. at 26 ±1.5°C), Heat-Low Condition [HLC] (3 m.a.s.l. at 30.5 ±0.6°C), and Cool-High Condition [CHC] (2369 m.a.s.l. at 14.2 ±0.6°C). Tensiomyography (TMG), Countermovement Jump (CMJ), and Delayed Onset Muscle Soreness (DOMS) were measured pre and post running. During the 30&#39; TT, distance, speed, heart rate (HR), rate of perceived exertion (RPE), and thermal index (WBGT) were measured. Results show a significant decrease in body weight and a significant increase in DOMS and jump height in CMJ after running in each condition. TMG responses increased maximum radial muscle displacement (Dm) and decrease...

European Journal of Applied Physiology, 2008

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 (waterperfusion garment: 40°C) and progressively increasing, exercise-related thermal strain (36°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 Wnal core temperature averaging 39.7°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 betweensite comparisons with the lateral torso diVered signiWcantly (P < 0.05), except for comparisons with the chest (P = 0.051) and shoulder (P > 0.05). The intra-segmental diVerences between the lateral torso and the chest, abdomen, upper-and lower-back areas were signiWcantly 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.

Temperature

The purpose of this study was to investigate local sweat rate (LSR) and sweat composition before and after active or passive heat re-acclimation (HRA). Fifteen participants completed four standardized heat stress tests (HST): before and after ten days of controlled hyperthermia (CH) heat acclimation (HA), and before and after five days of HRA. Each HST consisted of 35 min of cycling at 1.5W•kg −1 body mass (33°C and 65% relative humidity), followed by a graded exercise test. For HRA, participants were re-exposed to either CH (CH-CH, n = 6), hot water immersion (water temperature ~40°C for 40 min; CH-HWI, n = 5) or control (CH-CON, n = 4). LSR, sweat sodium, chloride, lactate and potassium concentrations were determined on the arm and back. LSR increased following HA (arm +18%; back +41%, P ≤ 0.03) and HRA (CH-CH: arm +31%; back +45%; CH-HWI: arm +65%; back +49%; CH-CON arm +11%; back +11%, P ≤ 0.021). Sweat sodium, chloride and lactate decreased following HA (arm 25-34; back 21-27%, P < 0.001) and HRA (CH-CH: arm 26-54%; back 20-43%; CH-HWI: arm 9-49%; back 13-29%; CH-CON: arm 1-3%, back 2-5%, P < 0.001). LSR increases on both skin sites were larger in CH-CH and CH-HWI than CH-CON (P ≤ 0.010), but CH-CH and CH-HWI were not different (P ≥ 0.148). Sweat sodium and chloride conservation was larger in CH-CH than CH-HWI and CH-CON on the arm and back, whilst CH-HWI and CH-CON were not different (P ≥ 0.265). These results suggest that active HRA leads to similar increases in LSR, but more conservation of sweat sodium and chloride than passive HRA.

2005

The effect of low-intensity exercise 1n the heat on thermoregulation and some biochem~cal changes in temperate and tropical subjects under poorly and well-hydrated states was examined. Two V02m£L-c matched groups of subjects consisting of 8 Japanese (JS) and 8 Malaysians (MS) participated in this study under two conditions. They are poorly-hydrated (no water was given) and well-hydrated (3 rnl. Kg-1 body weight of water was provided at onset of exercise, 15th, 35th and 55th min of exercise). Experimental room in both countries was adjusted to a constant level (Ta: 31.5±0.03°C, rh: 72.9±0.1 %). Subjects spent an initial 10 min rest, 60 min of cycling at 40% V02max and then 40 min recovery in the experimental room. Rectal temperatures (Tre) skin temperatures (Tsk), heart rate (HR), heat-activated sweat glands density (HASG), local sweat rate (Msw-back) and percent dehydration were recorded during the test. Blood samples were analysed for plasma glucose and lactate levels. The extent o...