Abstract
In order to investigate thermal and cardiovascular responses during exercise in lower (0500) and higher phases (1700) of core temperature (Tc, five healthy men (23-27 yrs) performed moderate cycle work at thermoneutraliy. We measured Tc and skin temperature, skin blood flow (SkBF), heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures. Mean arterial pressure (MAP; [SBP+2xDBP]/3) and rate of pressure product (RPP; HR x SBP) calculated. Cutaneous vascular conductance (CVC; SkBF/MAP) was expressed as percentage change from control rest (%CVCbase. Before exercise SkBF, HR and Tc were significantly higher in the evening than in the early morning. However, the circadian effect of cardiovascular responses, RPP, MAP and%CVCbase was masked by muscular work. It is concluded that there are no circadian effects of cardiovascular responses between lower Tc phase and higher Tc phase in the circadian cycle. [J Physiol Sci. 2008;58 Suppl:S102]
