EFFECT OF LUTEAL-PHASE ELEVATION IN-CORE TEMPERATURE ON FOREARM BLOOD-FLOW DURING EXERCISE

Forearm blood flow (FBF) as an index of skin blood flow in the forearm was measured in five healthy women by venous occlusion plethysmograph y during leg exercise at 80% peak aerobic power and ambient temperatur e of 35 degrees C (relative humidity 22%; dew-point temperature 10 deg rees C). Resting esophageal temperature (T-es) was 0.3 +/- 0.1 degrees C higher in the midluteal than in the early follicular phase of the m enstrual cycle (P < 0.05). Resting FBF was not different between menst rual cycle phases. The T-es threshold for onset of skin vasodilation w as higher (37.4 +/- 0.2 degrees C) in midluteal than in early follicul ar phase (37.0 +/- 0.1 degrees C; P < 0.05). The slope of the FBF to T -es relationship was not different between menstrual cycle phases (14. 0 +/- 4.2 ml . 100 ml(-1). min(-1).degrees C-1 for early follicular an d 16.3 +/- 3.2 ml . 100 ml(-1). min(-1).degrees C-1 for midluteal phas e). Plateau FBF was higher during exercise in midluteal (14.6 +/- 2.2 ml . 100 ml(-1). min(-1).degrees C-1) compared with early follicular p hase (10.9 +/- 2.4 ml . 100 ml(-1). min(-1).degrees C-1; P < 0.05). Th e attenuation of the increase in FBF to T-es occurred when T-es was 0. 6 degrees C higher and at higher FBF in midluteal than in early follic ular experiments (P < 0.05). In summary, the FBF response is different during exercise in the two menstrual cycle phases studied. After the attenuation of the increase in FBF and while T-es was still increasing , the greater FBF in the midluteal phase may have been due to the effe cts of increased endogenous reproductive endocrines on the cutaneous v asculature.