Sex- and condition-dependent muscle oxygenation, performance fatigability, and post-occlusive reactive hyperemic responses to blood flow restriction exercise.

PURPOSE: This study examined sex- and condition-dependent differences in muscle oxygenation, performance fatigability (PF), and post-occlusive reactive hyperemic responses during moderate-pressure (40% of arterial occlusion pressure) blood flow restriction exercise (BFR), free-flow exercise (NON-BFR), and BFR without exercise (PASSIVE BFR).

METHODS

Fifteen males and fourteen females completed all three conditions in a randomized crossover design. Exercise consisted of unilateral, dynamic leg extensions performed at 30% of maximal voluntary isometric contraction (MVIC) using a 30-15-15-15 repetition protocol with 60-s inter-set recovery periods. During intervention and recovery sets, muscle oxygenation (SmO2) and deoxygenated hemoglobin (HHb) were assessed using near-infrared spectroscopy (NIRS). Pre- and post-intervention MVIC torque, and vascular occlusion test (VOT)-derived post-occlusive reperfusion slope (Slope 2) were evaluated. Linear mixed-effects models were used, with significance set at p < 0.05.

RESULTS

Compared with NON-BFR and PASSIVE BFR, BFR elicited lower SmO2 and greater HHb during the intervention, lower reoxygenation during recovery, and larger reductions in MVIC. Slope 2 increased following the interventions when collapsed across conditions (p = 0.032), with no condition effect detected. Males exhibited lower SmO2, greater HHb responses, and larger reductions in MVIC during BFR and NON-BFR compared with females. When collapsed across conditions, males demonstrated greater Slope 2 than females (p = 0.003).

CONCLUSION

Although BFR induced marked intramuscular deoxygenation and greater fatigability in both sexes, we did not detect a corresponding enhancement in post-exercise reactive hyperemic response, a finding that should be interpreted cautiously given the limited reliability of Slope 2.