EFFECTS OF ENDURANCE TRAINING AND HEAT ACCLIMATION ON PSYCHOLOGICAL STRAIN IN PROTECTIVE CLOTHING 1212
Yukitoshi Aoyagi, Tom M. McLellan, Roy Jesse Shephard · Medicine & Science in Sports & Exercise · 1997
Two experiments examined the influence of endurance training and heat acclimation on ratings of perceived exertion (RPE) and thermal discomfort(RTD) during exercise in the heat while wearing two types of clothing. In Experiment 1, young men underwent 8 weeks of endurance training [60-80% of maximal aerobic power (˙VO2max) for 30-45 min/day, 3-4 days/week at 20-22°C] followed by 6 days of heat acclimation (45-55% ˙VO2max for 60 min/day at 40°C, 30% relative humidity) or corresponding periods of control observation followed by heat acclimation. In Experiment 2, young men were heat-acclimated for 6 or 12 days. Before and after each treatment, subjects completed bouts of treadmill exercise at 40°C, 30% relative humidity, wearing in turn normal clothing (continuous exercise at 30-45%˙VO2max) or protective clothing (continuous exercise at 40-50%˙VO2max in Experiment 1; intermittent exercise at 20-25%˙VO2max in Experiment 2). When wearing normal clothing, training or acclimation decreased RPE and/or RTD during the test exercise, with concomitant reductions in rectal temperature (Tre), mean skin temperature([horizontal bar over]Tsk), and/or heart rate (HR); acclimation responses were about twice as large after 12 than after 6 days. When wearing protective clothing, training did not change psychological or physiological responses. Acclimation reduced Tre and/or [horizontal bar over]Tsk when wearing protective clothing, irrespective of the duration of acclimation or the intensity of exercise, but RPE and/or RTD and HR were reduced only at the lower intensity of exercise. After training or acclimation, tolerance times were unchanged when exercising at the moderate intensity, but were increased by 10-15% when exercising at the low intensity. Because of sweat accumulation under the clothing, we conclude that acclimation only reduces the strain imposed by wearing protective garments only if a person is working at a low rate.