The Effect of Endurance Training with Heat Stress Added by Layered Clothing in Long Distance Runners

Abstract

The purpose of the present study is to clarify the effects of heat stress added by layered clothing during 3 days of endurance training on thermoregulatory during exercise in a hot environment among long-distance runners. Nine male long-distance runners conducted three consecutive days of endurance （cycling） training at 50% V･O2max for 90 min/day at 15℃ with layered clothing （WEAR condition） or short-sleeve shirts and short （CON condition）．Each condition was separated six weeks between conditions. Before and after training period, heat stress test （HST）， consisting of 40 min of endurance （cycling） exercise in a hot environment （35℃, 50%RH）， were conducted. During HST, core temperature, plasm volume, heart rate, sweat rate, sweat sodium concentration, score of thermal sensation and rate of perceived exertion were evaluated. Peak core temperature during training session was 38.39℃ in WEAR and 38.31℃ in CON, with no significant difference between conditions. The mean heart rate during training session was 126 bpm in WEAR and 120 bpm in CON （P>0.05 between conditions）．The average sweat rate during training sessions was significantly higher in WEAR （2.45%） vs. CON （1.31%） （P<0.001 between conditions）．The absolute changes in resting core temperature before and after training period were -0.97% （from 37.22℃ to 36.85℃） in WEAR and -0.82% （from 37.19℃ to 36.88℃） in CON, with no significant difference between conditions. The relative change in sweat rate after HST was 0.01% （from 1.01% to 1.03%） in WEAR and 8.87% （from 1.03% to 1.12%） in CON, with no significant difference between conditions. In conclusion, three consecutive days of endurance training adding heat stress by wearing layers didn’t improve thermoregulatory ability in a hot environment.