Effects of different full squat training volumes matched for fatigue on strength gains, neuromuscular adaptations, and muscle hypertrophy.

To investigate the effects of three full squat (SQ) training volumes, matched for fatigue, on jump performance, muscle strength, neuromuscular adaptations, and muscle hypertrophy. Thirty-six resistance-trained men were randomized into three groups: low (LOW), moderate (MOD), and high (HIG) volume. All groups trained SQ twice a week, with relative intensities increasing from 70% to 85% 1RM over the 8-week training period. The total volume accumulated was 48, 144, and 312 repetitions for LOW, MOD, and HIG, respectively, during the 16 training sessions. To isolate the effect of training volume by minimizing fatigue accumulation across repetitions, short rest periods were inserted between repetitions. The following tests were performed: 1) cross-sectional area (CSA) of vastus lateralis; 2) countermovement jump (CMJ); 3) maximal isometric SQ contraction; 4) progressive loading SQ test; and 5) fatigue SQ test. MOD achieved the greatest gains in the progressive loading SQ test ("group-by-time" interaction: p = 0.02, effect sizes (ES): 0.87, 2.52, and 1.12, for LOW, MOD, and HIG, respectively). HIG showed the greatest increases in the electromyography amplitude during this test ("group-by-time" interaction: p = 0.03, ES: -0.13, 0.52, and 0.88, for LOW, MOD, and HIG). All groups showed significant increases in CSA, without significant differences between them ("group-by-time" interaction: p = 0.34, ES: 0.52, 0.41, and 0.56, for LOW, MOD, and HIG). Short inter-repetition rest periods enabled all training volumes to induce significant hypertrophy, while moderate volumes optimized strength gains and high volumes maximized neuromuscular activation, highlighting volume-specific adaptations in SQ training.