Gender differences in brachial blood flow during fatiguing intermittent handgrip

Purpose: Females have been reported to have greater resistance to skeletal muscle fatigue than males. Blood flow, which plays an important role in supplying oxygen and nutrients to working muscles, may play an important role in the mechanisms of gender difference. We hypothesized that females would have greater conduit artery blood flow supplying working muscles than males during intermittent maximal handgrip exercise. Methods: Healthy adult (22-31 yr old) males (N = 8) and females (N = 8), lying in a supine position, repeated static maximal voluntary contractions (MVC) with a handgrip device in an intermittent pattern. Mean brachial arterial blood flow (MBABF) was continuously monitored using Doppler ultrasonography during the 5-s muscle-relaxation phase, when intramuscular pressure does not impede measurement of muscle blood flow during the 4-min exercise period, and continuously during the 10-min recovery period. Vascular conductance (VC) was calculated from the MBABF normalized by forearm volume and mean blood pressure (MBP). Results: Females achieved higher relative muscle force (%MVC) than males throughout both the exercise and the recovery periods (P < 0.05); females tended to exhibit smaller declines in muscle force (i.e., less fatigue). Exercise-induced increases in MBABF normalized to forearm volume were greater in females compared with males during the relaxation phases (P < 0.05), during which females also exhibited greater VC than males (P < 0.05). Conclusion: Our findings suggest that the normalized MBABF and VC in females, who experience less muscle fatigue, are greater during intermittent maximal voluntary handgrip exercise.