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Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation.

ABSTRACT: Purpose: Produce a detailed upper-body sweat map and evaluate changes in gross and regional sweating rates (RSR) and distribution following heat acclimation (HA). Methods: Six males (25 ± 4 yrs) completed six consecutive HA days (45°C, 20% rh) requiring 90 minutes intermittent exercise to maintain a 1.4°C rectal temperature (Tre) rise. Pre- and post-HA upper-body RSR were measured at 55% (Intensity-1; I1) and 75% VO2 max (Intensity-2; I2) using a modified absorbent technique. Results: From day one to six of HA, work rate increased (n.s.), heart rate, Tre, and skin temperature were similar, and gross sweat loss (GSL) increased (P < 0.001). During pre and post-HA experiments, relative workloads were similar (Pre-I1 54 ± 3, Post-I1 57 ± 5%VO2max; Pre-I2 73 ± 4, Post-I2 76 ± 7%VO2max). Post-HA GSL was significantly higher (Pre 449 ± 90 g.m-2 h-1, Post 546 g.m-2 h-1; P < 0.01). Highest RSR were observed on the central back both pre and post-HA at I1 (pre 854 ± 269 post 1178 ± 402g.m-2 h-1) and I2 (pre 1221 ± 351 post 1772 ± 396 g.m-2 h-1). Absolute RSR increased significantly in 12 (I1) to 14 (I2) of the 17 regions. Ratio data indicated significant post-HA relative RSR redistribution, with decreased relative contributions to whole-body sweating on the back, chest staying the same and arms increasing. Conclusions: Hot-dry HA significantly increased GSL in aerobically trained males at I2. Absolute RSR significantly increased in I1 and I2, with a preferential relative redistribution towards the periphery of the upper-body.

SUBMITTER: Smith CJ

PROVIDER: S-EPMC6422520 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation.

Smith Caroline J CJ Havenith George G

Temperature (Austin, Tex.) 20190207 1

Purpose: Produce a detailed upper-body sweat map and evaluate changes in gross and regional sweating rates (RSR) and distribution following heat acclimation (HA). Methods: Six males (25 ± 4 yrs) completed six consecutive HA days (45°C, 20% rh) requiring 90 minutes intermittent exercise to maintain a 1.4°C rectal temperature (Tre) rise. Pre- and post-HA upper-body RSR were measured at 55% (Intensity-1; I1) and 75% VO2 max (Intensity-2; I2) using a modified absorbent technique. Re ...[more]

PMID: 30906811

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Project description:Heat acclimation by post-exercise hot water immersion (HWI) on six consecutive days reduces thermal strain and improves exercise performance during heat stress. However, the retention of adaptations by this method remains unknown. Typically, adaptations to short-term, exercise-heat-acclimation (<7 heat exposures) decay rapidly and are lost within 2 weeks. Short-term protocols should therefore be completed within 2 weeks of relocating to the heat; potentially compromising pre-competition/deployment training. To establish whether adaptations from post-exercise HWI are retained for up to 2 weeks, participants completed a 40-min treadmill run at 65% max in the heat (33°C, 40% RH) before (PRE) and 24 h after (POST) the HWI intervention (n = 13) and then at 1 week (WK 1) and 2 weeks (WK 2) after the HWI intervention (n = 9). Heat acclimation involved a 40-min treadmill run (65% max) on six consecutive days in temperate conditions (20°C), followed by ≤40 min HWI (40°C). Post-exercise HWI induced heat acclimation adaptations that were retained for at least 2 weeks, evidenced by reductions from PRE to WK 2 in: resting rectal core temperature (T re, -0.36 ± 0.25°C), T re at sweating onset (-0.26 ± 0.24°C), and end-exercise T re (-0.36 ± 0.37°C). Furthermore, mean skin temperature (T sk) (-0.77 ± 0.70°C), heart rate (-14 ± 10 beats⋅min-1), rating of perceived exertion (-1 ± 2), and thermal sensation (-1 ± 1) were reduced from PRE to WK 2 (P < 0.05). However, PRE to POST changes in total hemoglobin mass, blood volume, plasma volume, the drive for sweating onset, sweating sensitivity and whole body sweating rate did not reach significance (P > 0.05). As such, the reduction in thermal strain during exercise-heat stress appears likely due to the reduction in resting T re evident at POST, WK 1, and WK 2. In summary, 6 days of post-exercise HWI is an effective, practical and accessible heat acclimation strategy that induces adaptations, which are retained for at least 2 weeks. Therefore, post-exercise HWI can be completed during an athlete's pre-taper phase and does not suffer from the same practical limitations as short-term, exercise-heat-acclimation.

Project description:BackgroundHeat application before peripheral intravenous catheterization is recommended for venous dilation. Hot pack application enlarges the venous diameter in healthy adults; however, hot towels (moist and dry heat) are used often in some medical cases. However, it is unclear whether hot towel application promotes venous dilation better than hot pack application. This study compared the venous dilation effect of using a hot towel (moist and dry heat) to a hot pack before applying the tourniquet at an access site for peripheral intravenous catheterization.MethodsEighty-eight healthy females aged 18-29 years were recruited for this quasi-experimental study. They underwent three types of heat applications (hot pack, moist hot towel, and dry hot towel [moist hot towel wrapped in a dry plastic bag], all of which were warmed to 40 ± 2 °C and performed for 7 min) to their forearm and tourniquet application for 30 s after each heating. Venous diameter and depth were measured using ultrasonography, and venous palpability and visibility (venous assessment score) was observed as venous dilatation effects. In addition, the skin temperature, stratum corneum hydration, and subjective evaluation of the warmth were measured.ResultsThere were no significant differences in venous diameter and assessment scores after intervention between the dry hot towel and the hot pack groups, and the effect size was negligible (Cohen's d < 0.20). However, these measurements were significantly lower for the moist hot towel than for the other two heat applications (P < .001). Although there was no significant difference in skin temperature and warmth rating score between the dry hot towel and the hot pack, these were significantly lower for the moist hot towel than for the other two heat applications (P < .001). The amount of change in stratum corneum hydration of the dry hot towel was not significantly different from that of the hot pack; however, that of the moist hot towel was significantly larger than that of the other two heat applications (P < . 001.) CONCLUSIONS: A method in which a towel warmed in hot water is wrapped in a dry barrier may be an alternative to a hot pack.Trial registrationThis study was registered with University Hospital Medical Information Network in Japan (Registration No.: UMIN000048308. Registered on July 7, 2022).

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Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation.

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Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation.

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