Sex Differences in Cardiac Baroreflex Sensitivity after Isometric Handgrip Exercise

PURPOSE: This study aimed to investigate potential sex-related differences on spontaneous cardiac baroreflex sensitivity (cBRS) after acute isometric handgrip (IHG) exercise. METHODS: Twenty men (age, 23 ± 3 yr) and 20 women (age, 24 ± 4 yr) randomly performed four sets of 2-min IHG exercise (two sets for each limb) at 30% maximal voluntary contraction (experimental) or 3% maximal voluntary contraction (sham). Beat-to-beat heart rate (HR) and arterial blood pressure (BP) were monitored using finger photoplethysmography before and 10, 20, and 30 min after IHG. Spontaneous cBRS was assessed via the sequence technique and cardiac autonomic modulation via time- and frequency-domain HR variability. RESULTS: After IHG, spontaneous cBRS increased during 10 min of recovery in men (Δ13% ± 5%, P = 0.03 vs rest) and increased further in women (Δ23% ± 4%, P < 0.01 vs rest; P = 0.04 vs men). During 20 and 30 min of recovery, cBRS returned to baseline in men but remained elevated in women. HR decreased 10 min after IHG in men (10 min: Δ-2 ± 1 bpm, P < 0.01 vs rest; 20 min: Δ-1 ± 1 bpm, P = 0.39 vs rest; 30 min: Δ1 ± 1 bpm, P = 0.31 vs rest) and throughout recovery in women (10 min: Δ-5 ± 1 bpm, P < 0.01 vs rest; 20 min: Δ-3 ± 1 bpm, P < 0.01 vs rest; 30 min: Δ-2 ± 1 bpm, P < 0.01 vs rest). Systolic BP increased 10 min after IHG and remained elevated during 20 min and 30 min in men (P < 0.05). In women, systolic BP increased during 10 min (P < 0.01) and returned to baseline during 20 and 30 min of recovery. Time-domain HR variability (root mean square of successive differences) was increased during recovery in men and women (P < 0.05). Sham had no effect on any variables. CONCLUSIONS: Acute IHG exercise increases cBRS and cardiac vagal activity in healthy young subjects, but the magnitude and the time course of changes in cBRS differ between men and women.