title: Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling.
abstract: The effect of slightly lowered body temperature on endurance time and possibly related physiological factors was studied in seven male volunteers exercising on a cycle ergometer at an ambient temperature (Ta) of 18 degrees C. Work load was increased to 40% in a stepwise manner (phase I, min 0-16) followed by a period at 80% of peak oxygen consumption (VO2) sustained to exhaustion. On one day, exercise was preceded by a double cold exposure (precooling test, PRET), resulting in a 204-kJ/m2 negative heat storage and a 4 and 0.2 degrees C lower mean skin and core temperature at the start of exercise compared with the control test (CONT). Core temperature dropped further during exercise in PRET. Endurance time at 80% of peak VO2 was increased by 12% (P less than 0.05) in PRET. Heart rate (HR) was decreased throughout PRET (P less than 0.05); oxygen pulse and arteriovenous O2 difference were significantly increased in phase I of PRET, whereas the PRET-CONT differences in stroke volume and cardiac output were not significant. In phase II of PRET (min 16-28, heavy exercise) sweat rate (SR) and heat conductivity, indicating forearm blood flow, were lower (-39%, P less than 0.001; -37%). Pedal rate (PR) was 9% lower (P less than 0.01) in phase II of PRET. At the termination of exercise, PRET-CONT differences in HR, SR, and PR had disappeared.
authors: Institute of Physiology, Justus Liebig University Giessen, Federal Republic of Germany.
authors: H
authors: H
authors: Olschewski
authors: K
authors: K
authors: Brück
mesh_terms: D000328:Adult; D001833:Body Temperature Regulation; D002320:Cardiovascular Physiological Phenomena; D006439:Hemodynamics; D006801:Humans; D007036:Hypothermia, Induced; D008297:Male; D009132:Muscles / Q000502:physiology*; D010101:Oxygen Consumption; D010807:Physical Endurance; D005082:Physical Exertion