The cutaneous vascular response to heat stress does not explain sex‐related differences in sudomotor activity

Abstract

Changes in skin blood flow can independently modulate changes in sweat production. These findings could explain the lower whole‐body sudomotor activity recently observed in females during exercise. We therefore examined potential sex‐differences in local cutaneous and whole‐limb vascular conductance during exercise in the heat (40°C). Eight males and eight females (follicular phase) performed three successive 30 min exercise bouts at fixed rates of metabolic heat production equal to 200, 250, and 300 W·m−2. Local sudomotor activity (ventilated capsule) and cutaneous vascular conductance (CVC, laser‐doppler) were measured on the back, chest, and forearm, while whole‐limb vascular conductance was measured at the forearm (FVC, venous occlusion plethysmography). Despite a similar requirement for heat loss during each exercise bout, increases in local sudomotor activity were significantly lower in females at each measurement site (p≤0.001). However, these differences were paralleled by similar CVC responses on the back (43 ± 2 vs. 47 ± 5%, p=0.195), chest (52 ± 5 vs. 48 ± 4%, p=0.705), and forearm (51 ± 3 vs. 60 ± 6%, p=0.212). Furthermore, FVC did not differ between sex throughout exercise (0.09 ± 0.01 vs. 0.10 ± 0.01 L·100 mL−1·min−1·mmHg−2, p=0.278). These results suggest that the lower sudomotor activity observed in females during exercise is not due to a different cutaneous vascular response. Supported by NSERC grant RGPIN‐298159‐2009.