Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage.

Vascular blood flow restriction (BFR) training stimulates muscle hypertrophy by increasing muscle activation and muscle swelling. Previous studies used expensive pneumatic cuffs, which may not be practical for regular use. The aim was to investigate the acute effects of low-intensity practical BFR (LI-pBFR) on muscle activation, muscle swelling, and damage. Twelve trained male participants completed a 30-, 15-, 15-, 15-repetition scheme at 30% of their leg press 1-repetition maximum under control and LI-BFR conditions. Under the LI-BFR trial, knee wraps were applied to the thighs at a pressure that resulted in venous, not arterial, occlusion. In the control trial, wraps were applied with zero pressure. Ultrasound-determined muscle thickness was recorded at baseline; 0 minutes post with wraps; 0, 5, and 10 minutes post without wraps. Muscle activation was recorded during warm-ups and on the final set of 15 repetitions. Indices of muscle damage (soreness, power, and muscle swelling) were also recorded. There was a condition by time effect for muscle thickness (p < 0.0001, effect size [ES] = 0.5), in which muscle thickness increased in the LI-pBFR condition 0 minutes post with wraps and through 5 minutes post without wraps. No changes occurred in the control. There was a condition by time effect for muscle activation (p < 0.05, ES = 0.2). The LI-pBFR had greater activation than the control did. There were no condition by time effects on indices of muscle damage. Our data indicate that practical BFR significantly increases muscle activation and muscle thickness without increasing indices of damage.