Effects of Different Velocity Loss Thresholds in Full Squat With and Without Blood Flow Restriction on Strength Gains, Neuromuscular Adaptations, and Muscle Hypertrophy

This study aimed to analyze the effects of four full-squat (SQ) training programs that differed in the blood flow condition [free flow (FF) versus restricted (BFR)] and in the velocity loss (VL) induced within the set (20% vs. 40%) on strength gains and muscle hypertrophy. Fifty-two strength-trained men followed an 8-week (16 sessions) SQ training program from 55% to 70% 1-repetition maximum (1RM) (FF20: n = 14; BFR20: n = 13; FF40: n = 12; BFR40: n = 13). The number of sets n = 13 per session and the inter-set recovery periods (2 min) were matched between groups. A 50% arterial occlusion pressure was applied and maintained during the inter-set recovery for BFR groups. The following tests were carried out before and after the training intervention: (1) cross-sectional area of the vastus lateralis (ACSA); (2) countermovement jump; (3) progressive loading SQ test; and (4) fatigue SQ test. No significant BFR × VL × time interactions were observed. For 1RM and strength-derived outcomes from the progressive loading test, significant VL × time interactions (p = 0.01–0.05) in favor of 20% VL groups were found. Regarding jump performance, a significant VL × time interaction (p = 0.02) also favored the 20% VL groups. A BFR × time interaction (p = 0.02) was observed in favor of the BFR condition for ACSA. Prescribing a certain level of effort through VL results in similar jump and strength performance improvements, regardless of blood flow condition, with optimal gains achieved at a moderate VL threshold (20%). Additionally, the BFR condition maximized muscle hypertrophy compared to FF, making it a valuable strategy for muscle growth.