Effects of sex and menstrual cycle on sweating during isometric handgrip exercise and postexercise forearm occlusion

Abstract

New findings: What is the central question of this study? Do sex and menstrual cycle modulate sweating during isometric handgrip exercise and muscle metaboreceptor stimulation? What is the main finding and its importance? Sex modulates sweating during isometric handgrip exercise, as indicated by the lower sweat output per gland in women than in men, but not during muscle metaboreceptor stimulation. Sweat output per gland during isometric handgrip exercise and muscle metaboreceptor stimulation were lower in the mid-luteal phase than in the early follicular phase in women. Cholinergic sweat gland sensitivity might explain, in part, the individual variation of the response. Our results provide new insights regarding sex- and menstrual cycle-related modulation of the sweating response.

Abstract: We investigated whether sex and menstrual cycle could modulate sweating during isometric handgrip (IH) exercise and muscle metaboreceptor stimulation. Twelve young, healthy women in the early follicular (EF) and mid-luteal (ML) phases and 14 men underwent two experimental sessions consisting of a 1.5 min IH exercise at 25 and 50% of maximal voluntary contraction (MVC) in a hot environment (35°C, relative humidity 50%) followed by 2 min forearm occlusion to stimulate muscle metaboreceptors. Sweat rates, the number of activated sweat glands and the sweat output per gland (SGO) on the forearm and chest were assessed. Pilocarpine-induced sweating was also assessed via transdermal iontophoresis to compare the responses with those of IH exercise and muscle metaboreceptor stimulation, based on correlation analysis. Sweat rates on the forearm and chest during IH exercise and muscle metaboreceptor stimulation did not differ between men and women in either menstrual cycle phase (all P ≥ 0.144). However, women in both phases showed lower SGO on the forearm and/or chest compared with men during IH exercise at 50% of MVC, with no differences in muscle metaboreceptor stimulation. Women in the ML phase had a lower forearm sweat rate during IH exercise at 50% of MVC (P = 0.015) and SGO during exercise and muscle metaboreceptor stimulation (main effect, both P ≤ 0.003) compared with those in the EF phase. Overall, sweat rate and SGO during IH exercise and muscle metaboreceptor stimulation were correlated with pilocarpine-induced responses (all P ≤ 0.064, r ≥ 0.303). We showed that sex and menstrual cycle modulate sudomotor activity during IH exercise and/or muscle metaboreceptor stimulation. Cholinergic sweat gland sensitivity might explain, in part, the individual variation of the response.

Keywords: eccrine sweat glands; heat loss response; muscle metaboreflex; thermoregulation; women.