Effects of partial blood flow restriction on the neuromuscular activity of the rectus femoris muscle during the squat task in physically active young people

Abstract

Introduction: Physical exercises with the application of partial blood flow restriction (PBFR) have been widely used for musculoskeletal rehabilitation and conditioning. However, the effect of PBFR on neuromuscular activity in the lower limbs has not yet been established. Objective: To investigate the effects of PBFR on neuromuscular activity in the muscles of the lower limbs during free squat exercises. Methods: Eight participants (aged 27-32 years) without complaints of musculoskeletal or cardiovascular diseases were evaluated. EMG electrodes were placed on muscles of the lower limb. In addition to the EMG signal, triaxial accelerometer signals were recorded to identify the concentric and eccentric phases of the squat. A pneumatic cuff was positioned in the proximal region of each thigh, and 1x15 repetitions of free squats (knees flexed at approximately 90 degrees) were performed with both cuffs deflated (no-PBFR). After inflation of one of the cuffs (preferred lower limb; 60% of the total occlusion pressure of the popliteal artery), 1x30 repetitions followed by 3x15 repetitions (PBFR condition) of free squats were performed with a 60-second interval between sets. The coefficient of variation (CV) of the EMG signal from the rectus femoris (RF) during the concentric phase of the squat was calculated. Comparison between moments and conditions was performed using ANOVA. Results: We observed a significant interaction between moment and condition (P=0.029, η2=0.118). As there was no post-test effect (P>0.138), an effect size analysis was performed. There were differences in EMG activity even in the pre-PBFR condition. After blood flow restriction, there was a reduction in EMG activity in the PBFR limb, accompanied by increases in EMG activity in the contralateral limb without PBFR. The differences between moments were greater in the PBFR condition (η2=0.226). Conclusion: PBFR increased neuromuscular activity in the contralateral limb to the stimulus. Further studies are necessary to confirm this effect.