Similar acute increases in muscle size, but discrete perceptual responses to low-load blood flow restriction protocols

Abstract

The purpose of this investigation was to assess muscle size and perceptual responses following acute bouts of low-load blood flow restriction resistance exercise performed with a 75-repetition (1 × 30, 3 × 15), 3 sets to failure, and a 1 set to failure protocols. Nineteen females randomly performed a 75-repetition, 3 sets to failure, and 1 one set to failure low-load blood flow restriction protocols consisting of unilateral, submaximal (30% of maximal voluntary isometric contraction), isokinetic (90°·s⁻¹), leg extension muscle actions. The minimal difference (MD) was used to determine real changes in each dependent variable from pretest to posttest. There were no significant (p = 0.191–0.567) interactions, main effects of Condition (p = 0.108–0.931), or main effects of Muscle (p = 0.103–0.958) for muscle thickness (MTH), cross-sectional area (CSA), or echo intensity (EI) of the rectus femoris or vastus lateralis. Across the protocols, the changes in MTH, CSA, and EI exceeded the minimal difference for 16–19, 18–19, and 11–19 of the 19 participants, respectively. Following the final set of each protocol, 3 sets to failure (8.94 ± 1.07 au) resulted in a greater rating of perceived exertion compared to the 1 set to failure (8.02 ± 1.08 au) and 75-repetition (8.05 ± 1.35 au) protocols. All three protocols resulted in comparable acute changes in muscle size; however, the 3 sets to failure resulted in the greatest perceptual response. Therefore, comparable acute muscle size responses can be achieved with the 75-repetition protocol or one set performed to failure with a reduced level of exertion.