Brachial blood flow and pressure responses are unrelated to the greater isometric handgrip tolerance of females compared to males

Isometric handgrip (IHG) training lowers blood pressure (BP), but sex differences in fatigability may be confounding. We hypothesized that the greater time-to-fatigue during IHG in females would relate to preserved brachial blood flow, with males exhibiting reductions in flow. Fifteen females and 14 males (18–32 years) completed a fatiguing IHG at 30% of maximum voluntary contraction (MVC). Brachial diameter and blood velocity were assessed with B-mode and Doppler ultrasound, and BP via beat-to-beat finger photoplethysmography. Both sexes exhibited similar non-significant increases in brachial flow during IHG (Δ_HG-rest = 30 mL min⁻¹, p = 0.200). Post-exercise hyperemia was greater in males (Δ15_spost-rest = 182 mL min⁻¹, 95% CI: 130–233 mL min⁻¹, p < 0.001) than in females (Δ15_spost-rest = 89 mL min⁻¹, 95% CI: 39–138 mL min⁻¹, p < 0.001). Despite the mean arterial pressure response being greater in males (Δ = 30 mmHg, 95% CI: 24–37 mmHg, p < 0.001; vs. Δ = 17 mmHg, 95% CI: 10–23 mmHg, p < 0.001), conductance was similar between sexes during IHG (p = 0.470). Time-to-fatigue was greater in females (243-s vs. 181-s, p = 0.021) and unrelated to flow. Controlling for MVC, brachial diameter, or arm circumference did not affect results. Brachial flow and pressor responses were unrelated to the greater fatigue resistance of young females. The greater post-exercise hyperemia in males suggests a greater ischemic stimulus, independent of blood flow.