Effects of velocity loss with blood flow restriction in full squat on strength gains, neuromuscular adaptations, and muscle hypertrophy

Abstract

To analyse the effects of four full squat (SQ) training programmes with different velocity loss (VL) thresholds (0%, 10%, 20%, and 40%) with blood flow restriction (BFR) implementation on muscle size, lower limb strength, and neuromuscular adaptations. Forty-six strength-trained men carried out an 8-week (16 sessions) SQ training programme with BFR that differed in the VL attained within the set: BFR 0% VL (BFR0, n = 11), BFR 10% VL (BFR10, n = 11), BFR 20% VL (BFR20, n = 11), and BFR 40% VL (BFR40, n = 13). The same inter-set recovery (2 minutes), sets (3), intensity (from 55% to 70% 1RM), and level of BFR (50% of arterial occlusion pressure) were established for all groups. Before and after the training intervention, the following tests were carried out: 1) vastus lateralis muscle size; 2) countermovement jump; 3) maximal isometric SQ test; 4) progressive loading SQ test; and 5) fatigue SQ test. Muscle hypertrophy increased as the VL increased ("group × time" interaction: p = 0.013). Only BFR20 significantly improved force production at various time intervals ("group × time" interactions: p ≤ 0.05). Moreover, effect sizes suggest that low-to-moderate VL thresholds maximize the improvements in SQ strength against different loads (BFR0: 0.47-1.75; BFR10: 0.61-1.96; BFR20: 0.71-2.18; BFR40: 0.38-1.53). In BFR contexts, low-to-moderate VL thresholds should be prescribed to optimize leg strength performance. Extremely low VL (i.e., 0%) seemed insufficient to maximize strength gains, while higher VL thresholds are more effective for promoting muscle hypertrophy but may somewhat compromise strength improvements.