Effects of movement velocity in squat training with and without blood flow restriction

This study compared the effects of four different resistance training (RT) programs that differed in the movement velocity [maximum (MaxV) vs. 50% of maximum voluntary velocity (HalfV)] and the blood flow condition [free (FF) vs. restricted (BFR)] on strength, neuromuscular, and hypertrophy adaptations. Fortysix resistance-trained males were randomly assigned to one of the four abovementioned protocols. Subjects followed an 8-week RT program, twice per week, with similar intensity (55%-65% 1RM), sets (3), and repetitions per set (10-6) in the full-squat (SQ) exercise. Before and after the RT program, they were evaluated for: 1) muscle size of the vastus lateralis; 2) vertical jump; 3) maximal isometric contraction; 4) progressive loading test; and 5) fatigue test, in SQ. Electromyographic (EMG) activity was assessed during all SQ tests. All protocols exhibited significant gains in strength-derived parameters without significant differences between groups. A BFR × VEL × time interaction (p = 0.05) was observed for countermovement jump, with improvements in the HalfV-BFR and MaxV-FF protocols. A VEL × time interaction (p = 0.03) was found for the EMG amplitude under light loads, since HalfV-BFR increased its values. MaxV-BFR and HalfV-FF induced greater hypertrophy in the distal region of the vastus lateralis (BFR × VEL × time interaction, p = 0.04), with MaxV-BFR producing the greatest gains in all sections. Both MaxV-FF and HalfV-BFR increased CMJ height. HalfV-BFR also increased neuromuscular activity against light loads. MaxV-BFR and HalfV-FF evoked higher hypertrophy in muscle size, with the greatest gains in muscle size with MaxV-BFR.