Different Set And Repetition Schemes Induce Similar Neuromuscular Responses During Low-load Blood Flow Restriction Exercise

Purpose: The utility of low-load blood flow restriction (LLBFR) resistance exercise has been thoroughly investigated, although numerous protocols have been used without justification. Therefore, the purpose of this investigation was to examine the acute effects of three commonly used LL-BFR protocols on neuromuscular function. Methods: Seventeen (22.6 ± 4 years, 163.7 ± 5.3 cm, 70.1 ± 18.1 kg) recreationally active females visited the laboratory on five separate occasions. Participants randomly completed a 75 repetition (75rep; 1 × 30, 3 × 15), 3 sets to failure (3×), and 1 set to failure (1×) protocols consisting of unilateral, submaximal (30% of maximal voluntary isometric contraction), isokinetic (90°·s-1), leg extension muscle actions. Surface electromyography (sEMG) was recorded from the vastus lateralis muscle and was normalized to the first repetition during set 1 of each protocol. sEMG amplitude (AMP) and mean power frequency (MPF) were derived as the average of the first 5 repetitions completed during set 1 and the last 5 repetitions completed during the final set of each protocol. Separate 3 (Condition [75rep, 3×, 1×]) x 2 (Time [first 5 and final 5]) repeated measures ANOVAs were used to examine sEMG AMP and MPF. Results: There were no significant (p = 0.069-0.883) two-way interactions or main effects of Condition (p = 0.668-0.879), but there were significant (p < 0.001) main effects of Time for sEMG AMP and sEMG MPF. Specifically, from the first 5 to the final 5 repetitions, sEMG AMP increased (118.8 ± 32.8% to 203.74 ± 77.96%; p < 0.001; g = 0.959) and sEMG MPF decreased (100.32 ± 5.77 to 84.47 ± 15.50%; p < 0.001; g = -1.041). Conclusions: All LLBFR protocols necessitated large increases in muscle excitation (sEMG AMP) and induced reductions in action potential conduction velocity (sEMG MPF). The lack of differences among protocols suggested that each protocol was equally effective at altering motor unit activation strategies. Thus, maximizing acute neuromuscular changes can be accomplished in as little as 1 set of LLBFR performed to failure, but it remains to be determined if 1 set will achieve comparable chronic changes in neuromuscular and/or muscular function.