Practical Blood Flow Restriction Training Increases Acute Determinants of Hypertrophy Without Increasing Indices of Muscle Damage

Abstract

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.

Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development

“…While using elastic knee wraps for BFR makes it difficult to apply the restrictive stimulus at an exact pressure, Wilson et al [48] have shown this method is effective when wraps are applied to be snug, but not cause pain. These investigators standardized the restrictive stimulus using a perceived pressure scale from 0-10, with a score of 0 indicating no pressure, and 10 indicating intense pressure with pain [48].…”

“…These investigators standardized the restrictive stimulus using a perceived pressure scale from 0-10, with a score of 0 indicating no pressure, and 10 indicating intense pressure with pain [48].…”

“…Wilson et al [48] proposed that wraps should be applied so that a score of 7 (moderate pressure with no pain) is achieved, as this corresponded with occluded venous return without stopping arterial inflow. However, recent data from our laboratory (JPL, unpublished findings) do not find large differences in ratings of discomfort during exercise across a variety of pressures, indicating that perception may not provide the best estimate of actual restriction.…”

“…A BFR resistance exercise protocol that has become popular in recent research is 4 sets of an exercise, with goal repetitions of 30 in the first set, and 15 in sets 2-4, for a total of 75 repetitions [47,48,55,69]. While the optimal resistance training protocol for BFR exercise has not been firmly established, this repetition scheme has been demonstrated to aid in rehabilitation from knee injury [70], enhance acute muscle activation [48] and increase muscle strength and size [53], without increasing indices of muscle damage [47,48,69].…”

“…While the optimal resistance training protocol for BFR exercise has not been firmly established, this repetition scheme has been demonstrated to aid in rehabilitation from knee injury [70], enhance acute muscle activation [48] and increase muscle strength and size [53], without increasing indices of muscle damage [47,48,69]. As the cuff is applied immediately before the first set, there is no substantial accumulation of metabolites, and participants can perform a high number of repetitions in the first set.…”