The effect of heat stress on circulation in an exercising leg was determined using one-legged knee extension and two-legged bicycle exercise, both seated and upright. Subjects exercised for three successive 25-min periods wearing a water-perfused suit: control [CT, mean skin temperature (Tsk) = 35 degrees C], hot (H, Tsk = 38 degrees C), and cold (C, Tsk = 31 degrees C). During the heating period, esophageal temperature increased to a maximum of 37.91, 39.35, and 39.05 degrees C in the three types of exercise, respectively. There were no significant changes in pulmonary O2 uptake (VO2) throughout the entire exercise period with either one or two legs. Leg blood flow (LBF), measured in the femoral vein of one leg by thermodilution, remained unchanged between CT, H, and C periods. Venous plasma lactate concentration gradually declined over time, and no trend for an increased lactate release during the heating period was found. Similarly, femoral arteriovenous O2 difference and leg VO2 remained unchanged between the three exercise periods. Although cardiac output (acetylene rebreathing) was not significantly higher during H, there was a tendency for an increase of 1 and 2 l/min in one- and two-legged exercise, respectively, which could account for part of the increase in total skin blood flow during heating (gauged by changes in forearm blood flow). Because LBF was not reduced during exercise and heat stress in these experiments, the additional increase in skin blood flow must have been met by redistribution of blood away from vascular beds other than active skeletal muscle.

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A group of seven males was tested inside a thermobarochamber. Every subject was examined in the same manner in a simulated altitude of: 2500, 3500, 4500 m o.s.1. (control at 115 m 0.5.1.) After 20 minutes of adaptation the 25 minutes exposition to altitude hypoxia was performed. Thermovisual measurement (AGEMA Thermovision 900 series) was repeated at 5 min. intervals. The results demonstrated that the range and dynamics of temperature distribution were proportional to the intensity of altitude hypoxia and the exposure time. Observed changes depend on the area of body surface.

The paper was prepared as a part of the grant titled: "Improving the psychophysical fi tness of a soldier during combat tasks by means of pharmacological stimulation." Contract no. 0042/R/T00/2009/08. The project was co-fi nanced by the Ministry of Science and Higher Education.