The effect of a failure and submaximal blood flow restriction resistance exercise protocol on changes in muscle size, strength and swelling

Abstract

Introduction: Blood flow restricted resistance exercise (BFRRE) can induce rapid increases in muscle size, strength and swelling. No previous research has investigated the importance of conducting BFRRE to voluntary failure and few studies has been carried out to investigate associations between swelling and muscle size. Therefore, the aim of the present study was twofold (1) compare changes in muscle size and strength between a failure (FA) and submaximal (SU) BFRRE protocol (2) investigate associations between swelling and muscle size. Methods: Seventeen untrained men had their legs randomized to FA and SU protocols. The intervention consisted of two training periods including seven BFRRE sessions within five days (separated with 10 days’ rest) using unilateral knee extension at 20% of one repetition maximum (1RM) (30 s rest between sets). Swelling and muscle size was measured with ultrasound, whereas strength was measured as 1RM and maximal voluntary contraction (MVC). Results: Cross-sectional area (CSA) of rectus femoris increased significantly in both groups compared to baseline (FA: 7.9 ± 7.6%; p < 0.001 and SU: 9.1 ± 10.8%; p = 0.003), where no differences in muscle size were observed between groups. Strength (1RM) increased significantly in both groups (FA: 9±8%; p < 0.001 and SU: 11±7%; p < 0.001) at 24 days’ post intervention, whereas no group differences were found. Swelling increased CSA of rectus femoris (12.0±9.72%, p<0.001) compared to ultrasound measurement obtained right before BFRRE. Conclusion: FA and SU induced similar gains in muscle size and strength. Acute swelling increased, whereas no associations was observed between swelling and muscle size Keywords: ultrasound, blood flow restriction resistance exercise, concentric failure, submaximal, muscle thickness, cross-sectional area, swelling