Sex differences in beat-to-beat blood pressure variability following isometric handgrip exercise

Isometric handgrip (IHG) exercise lowers resting blood pressure (BP) and may modulate autonomic control, but its acute effects on beat-to-beat blood pressure variability (BPV) and sex-specific responses are unclear. We examined the impact of a single IHG bout on beat-to-beat BPV in healthy young adults, focusing on sex differences.

Thirty-eight subjects (20 men, 18 women) completed randomized, sham-controlled crossover trials: true IHG (30% MVC) and sham (3% MVC), each followed by 30 min of seated recovery. Continuous beat-to-beat BP, cardiac output (CO), and total peripheral resistance (TPR) were recorded. Variability was quantified via standard deviation (SD), range, interquartile range (IQR), coefficient of variation (CV), and average real variability (ARV).

Beat-to-beat systolic blood pressure (SBP) variability showed marked sex- and time-dependent changes, with no trial-condition effects. In men, SBP SD rose from 6.2 ± 1.4 mmHg at rest to 6.7 ± 2.0 mmHg at 30 min (P < 0.05), whereas women's SD remained at 5.6 ± 1.4 to 5.1 ± 1.6 mmHg (P > 0.05; sex P = 0.018; time P = 0.024). Range and IQR followed SD rising in men at 30 min but stable in women (sex P = 0.022 and P = 0.037). CO ARV increased in men (239 ± 65 to 275 ± 75 mL/min; P < 0.05) but remained stable in women (224 ± 45 to 233 ± 61 mL/min; P > 0.05; sex × condition P = 0.026). TPR variability (SD, IQR, CV, ARV) exhibited a significant effect of time (P ≤ 0.002), with no differences between sexes or condition.

A single IHG session does not acutely reduce beat-to-beat BPV in healthy young adults. Nevertheless, clear sex differences in beat-to-beat BPV responses highlight distinct autonomic and vascular regulation mechanisms.