Lower limb blood flow responses during higher- and lower-load bilateral leg press exercise

The local blood flow response to resistance exercise (RE) is complicated by local muscular contractions and large swings in perfusion pressure. The magnitude of these responses might vary according to exercise intensity, number of sets and number of repetitions, and as a result, the local shear environment during RE remains uncharacterized. We examined the effect of RE on superficial femoral artery (SFA) blood flow and shear rate during bilateral leg press in healthy males and females. Twenty-four healthy adults (24 ± 3 years; 14 female) performed either higher-load lower-repetition (75% 1-repetition maximum (RM); 8 reps/set for 3 sets) or lower-load higher repetition (35% 1-RM; 20 reps/set for 3 sets) incline leg press to failure in a random counterbalanced order. The SFA was imaged via duplex ultrasound, and the probe was secured on the right thigh using a limb-affixed probe holder for continuous imaging of blood velocity. Arterial diameter could not be reliably measured during exercise; exercising blood flow and shear rate were estimated from arterial diameters calculated 10 s post-exercise. Regardless of loading protocol, RE was characterized by increases in mean blood velocity, blood flow, anterograde shear and retrograde shear rate during exercise (time effects P < 0.01; comparisons P < 0.05), followed by reactive hyperaemia during rest periods with elevated mean shear and an abolished retrograde shear response. Arterial diameter increased only during rest periods between sets, consistent with the hyperaemic stimulus (P < 0.01). This research directly addresses our current knowledge gap regarding the vascular response to RE across different intensities of large muscle group exercise.