Abstract

Ten women exercised for 15 min on a cycle ergometer in the middle of the luteal phase (L) and in the early follicular phase (F) of the menstrual cycle at the same constant work rates (mean 122 W) and an ambient temperature of 18 degrees C. Serum progesterone averaged 44.7 mnol/l in L and 0.7 nmol/l in F. After a 4-h resting period, exercise was performed between 3 and 4 A.M., when the L-F core temperature difference is maximal. Preexercise esophageal (Tes), tympanic (Tty), and rectal (Tre) temperatures averaged 0.6 degree C higher in L. During exercise Tes, Tty, and Tre averaged 0.5 degree C higher. The thresholds for chest sweating and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were elevated in L by an average of 0.47 degree C, related to mean body temperature (Tb(es) = 0.87 Tes + 0.13 Tskin), cutaneous heat clearances were also increased in L. The mean exercise heart rate was 170.0 beats/min in L and 163.8 beats/min in F. The mean exercise VO2 in L was increased in L by 5.6, but the net efficiency was 5.3 lower. In conclusion, under specified conditions short-lasting heavy exercise in L is performed with higher core temperature and higher thermoregulatory, circulotory, and aerobic-metabolic strain than in F. Verf.-Referat