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F-13 Thematic Poster - Thermoregulation and Heat Stress Friday, June 3, 2016, 1: 00 PM - 3: 00 PM Room: 110

Increasing Skin Temperature During Exercise Lowers Stroke Volume Without Increasing Cutaneous Blood Flow.

2890 Board #4 June 3, 1

00 PM - 3

00 PM

Chou, Ting-Heng; Allen, Jakob R.; Hahn, Dongwoo; Montzingo, Luke J.; Leary, Brian K.; Coyle, Edward F. FACSM

Author Information
Medicine & Science in Sports & Exercise: May 2016 - Volume 48 - Issue 5S - p 809
doi: 10.1249/01.mss.0000487425.61018.18
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Both skin (Tsk) and core temperature (Tc) are elevated in most studies of heat stress during exercise and this is accompanied by increased heart rate (HR) and decreased stroke volume (SV). However, only a few studies have systemically investigated the effect of progressively increasing Tsk on cardiovascular responses during exercise.

PURPOSE:To systemically investigate how progressive increases in Tsk (32 to 40°C) affects cardiovascular responses and Tc during moderate exercise.

METHODS: Subjects (n=8, active men 25±1 y) cycled at 60% VO2peak for 20-30 min. Tsk was manipulated by wearing a water perfused suit that covered the whole body, except head, hands, and feet and maintained a perfused water temperature of 20, 30, 40, and 50°C. Subjects performed all four trials separated by at least 72 h. Esophageal temperature (Tes), Tsk, VO2, Q, HR, mean arterial pressure (MAP), cutaneous blood flow (CBF), and forearm venous volume (FVV) were measured during exercise.

RESULTS: Tsk was significantly different between all trials (P < 0.01) and averaged 32.4 ± 0.2, 35.5 ± 0.1, 37.5 ± 0.1, and 39.5°C ± 0.1°C, respectively. Tes was significantly different between each trial after 16 min of exercise (p < 0.05) and at the end of exercise were 37.6 ± 0.2, 38.3 ± 0.1, 39.2 ± 0.1, and 39.2 ± 0.2°C, respectively. The graded heating of Tsk resulted in a graded increase of HR and decrease of SV. However, CBF during exercise reached a similar average plateau value in all trials when Tes was above 38°C independent of Tsk. There was no apparent effect of Tsk on FVV, VO2, Q, and MAP.

CONCLUSIONS: Graded increases of Tsk from 32 to 40°C progressively increased Tes and HR and decreased SV during moderate exercise. Tsk had no effect on CBF when Tes was above 38°C. High Tsk (39.5 ± 0.1°C) did not elicit higher CBF and FVV compared to low Tsk during moderate exercise. CBF and FVV responses suggest no further blood pooling in the forearm skin when Tsk is increased from 32.4 to 39.5°C. The decrease of SV during exercise when heating the skin is related to an increase of HR but not an increase in CBF.

© 2016 American College of Sports Medicine