Circulatory responses at the onset of isometric exercise: does sex matter?
: blood pressure, systemic vascular resistance, sympathetic cholinergic vasodilation, isometric exercise.
The cholinergic vasodilation plays an important role in the blood pressure (BP) and systemic vascular resistance (SVR) responses at the onset of isometric handgrip exercise. Herein, we tested the hypothesis that women present an attenuated fall in SVR and increased pressor response compared to men at the onset of isometric handgrip exercise due to a blunted sympathetic cholinergic vasodilation. Twenty (10 women) young and healthy volunteers (average age: 22 ± 1 years old) were recruited. Participants performed 20s bout of isometric handgrip exercise at 40% of maximal voluntary contraction. Heart rate (HR), mean BP, stroke volume (SV), cardiac output (CO), and SVR responses to exercise were expressed as a change from 10s immediately before the voluntary contraction. Men demonstrated a drop in SVR at 3s (Δ-0.9 ± 0.3 mmHg.L-1 .min), 10s (Δ -1.6 ± 0.4 mmHg.L-1 .min) and 20s (Δ-1.9 ± 0.7 mmHg.L-1 .min) of the onset of isometric exercise, and these responses tend to be attenuated in women (3s: Δ-0.3 ± 0.3 mmHg.L-1 .min; 10s: Δ-1.2 ± 0.4 mmHg.L-1 .min; 20s: Δ-0.6 ± 0.5 mmHg.L-1 .min; P=0.131). While men present a typical exercise-evoked biphasic mean BP response, women show a progressive increase in BP at the onset of exercise. There are no sex differences in HR, SV and CO responses to exercise, which all increased progressively over the 20s of handgrip bout. These findings demonstrated a lack of sex differences in SVR and BP responses at the onset of isometric handgrip exercise, suggesting that the sympathetic cholinergic vasodilation contribution to circulatory responses at the beginning of exercise is irrespective of sex.