The physiological responses to walking uphill under hot environment.

A series of human experiments on walking uphill under radiant heat in addition to hot environment were carried out and the safety conditions for walking uphill from the standpoint of physiological response were determined. Experiments were carried out on three healthy adult males aged 21 years, walking uphill on a motor-driven treadmill with the aim of walking at a speed of 45 m/min, 55 m/min and 65 m/min and with a slope gradient of 0 degrees, 5 degrees and 10 degrees. The load weight used was 30, 40 and 50 percent of the body weight for each combination of speed, gradient and load weight. The subjects were exposed to a radiant heat of 1.3 cal/cm2.min, using 12 exsiccating infrared lamps, with a room temperature of 33 degrees C, a relative humidity of 60% and an airflow of 0.7 m/sec. The following results were obtained by estimating the physiological response (heart rate, respiration rate, rectal temperature and RMR (relative metabolic rate)) to different degrees of walking conditions during the 10-minute exercise: 1) The work intensity (RMR) of uphill walking with a certain load weight under hot environment can be changed by varying the walking speed and the load weight according to the slope gradient. 2) As there exists a gap between RMR 5 and 6 in parallel with the other physiological responses, it is preferable to keep the walking condition under RMR 6, as viewed from the change of the other walking conditions. 3) The heart rate as an indicator of the work load must be kept below 130 beats/min for a safe uphill walking of under RMR 6.