Submitted on February 18, 2008
Accepted on August 7, 2008
Menstrual cycle and oral contraceptive use do not modify post-exercise heat loss responses
Glen P. Kenny1*, Emily E. Leclair1, Ronald J. Sigal2, W. Shane Journeay3, Donald Kilby4, Lindsay Nettlefold1, Francis D. Reardon1, and Ollie Jay5
1 Human Kinetics, University of Ottawa, Ottawa, Canada
2 Medicine and Cardiac Sciences, University of Calgary, Calgary, Canada
3 Faculty of Medicine, Dalhousie Medical School, Halifax, Canada
4 Health Services, University of Ottawa, Ottawa, Canada
5 School of Human Kinetics, University of Ottawa, Ottawa, Canada
* To whom correspondence should be addressed. E-mail: gkenny{at}uottawa.ca.
We evaluated the effect of menstrual cycle and OC use on the activation of heat loss responses during a passively induced hyperthermia post-exercise. Females with (n=8) or without (n=8) OC underwent pre- and post-exercise passive heating during the early-follicular-phase (FP) and mid-luteal-phase (LP). Since OC use inhibits ovulation, a quasi-early-FP (q-FP) and quasi-mid-LP (q-LP) was assumed for the OC group. After a 60-min habituation at 26°C, subjects donned a liquid conditioned suit. Mean skin temperature was clamped at ~32.5°C for ~15 min and then gradually increased, and the absolute esophageal temperature at which the onset of forearm vasodilation (Thvd) and upper back sweating (Thsw) were noted. Subjects then cycled for 30-min at 75%VO2peak followed by 15-min seated recovery. A second passive heating was then performed to establish post-exercise values for Thvd and Thsw. Between 2 and 15-min post-exercise, MAP remained significantly below baseline (P<0.05) by 10±1 and 11±1 mmHg for the FP/q-FP and LP/q-LP respectively. MAP was not different between cycle phases. During LP/q-LP, Thvd was 0.16±0.24°C greater than FP/q-FP pre-exercise (P=0.020) and 0.15±0.23°C greater than FP/q-FP post-exercise (P=0.017). During LP/q-LP, Thsw was 0.17±0.23°C greater than FP/q-FP pre-exercise (P=0.016) and 0.18±0.16°C greater than FP/q-FP post-exercise (P=0.001). Post-exercise thresholds were significantly greater (P≤0.001) than pre-exercise during both FP/q-FP (Thvd:0.22±0.03°C; Thsw:0.13±0.03°C and LP/q-LP (Thvd:0.21±0.03°C; Thsw:0.14±0.03°C) however the effect of exercise was similar between LP/q-LP and FP/q-FP. No effect of OC use was observed. We conclude neither menstrual cycle nor OC use modifies the magnitude of the post-exercise elevation in Thvd and Thsw.
