Self-selected vs. Fixed Repetition Duration: Effects on Number of Repetitions and Muscle Activation in Resistance-Trained Men

Abstract

Nóbrega, SR, Barroso, R, Ugrinowitsch, C, da Costa, JLF, Alvarez, IF, Barcelos, C, and Libardi, CA. Self-selected vs. fixed repetition duration: effects on number of repetitions and muscle activation in resistance-trained men. J Strength Cond Res 32(9): 2419-2424, 2018-The aim of this study was to compare the effects of self-selected and fixed repetition duration (RD) on resistance exercise (RE) volume, muscle activation, and time under tension (TUT) per repetition and per session. Twelve resistance-trained men participated in the study. A randomized cross-over design was used and each participant performed 2 high-intensity RE protocols in a balanced order: (a) 3 sets of RE with self-selected RD (SELF); and (b) 3 sets of RE with fixed RD (2-second concentric and 2-second eccentric [FIX]). Muscle activation was assessed through surface electromyography (EMG) of the vastus lateralis and vastus medialis throughout RE sessions. Overall, RE volume was significantly greater for SELF (p = 0.01), whereas TUT per repetition was significantly greater for FIX (p = 0.0001). No significant differences between protocols were detected for TUT per session. Between-protocol comparisons revealed significantly greater EMG amplitude for SELF compared with FIX at S1 (p = 0.01), S2 (p = 0.03), and S3 (p = 0.03). Both SELF and FIX protocols produced significant increases in EMG amplitude from 25 to 100% (p < 0.001) of set completion. Between-protocol comparisons revealed significantly greater EMG amplitude for SELF compared with FIX at 75% (p = 0.03) and 100% (p = 0.01). In conclusion, self-selected RD resulted in greater volume and muscle activation compared with fixed RD in an RE session.

Effects of resistance training with controlled versus self-selected repetition duration on muscle mass and strength in untrained men

“…In our study, we observed increases between 10-14% in maximal strength and 7-10% in muscle hypertrophy after 8 weeks, which is in line with a previous study also performed with untrained subjects (Ahtiainen et al, 2016). Additionally, we demonstrated that SELF results in greater number of repetitions per session and VL, which was also observed in a previous study from our laboratory (Nobrega et al, 2018a). Nevertheless, the increase in muscle strength and hypertrophy was similar to the RT protocols with lower volume (CON and SELF-EV), contradicting our initial hypothesis.…”

“…Fifth: Unfortunately, the TUT per repetition throughout the set was not controlled. However, a study from our laboratory used an electrogoniometer to check the variation of TUT within the same set during SELF and CON protocols (Nobrega et al, 2018a). The results showed that TUT per repetition in the SELF protocol increased throughout the sets, possibly due to accumulated fatigue.…”

“…Other acute studies have also shown that SELF and CON can affect resistance exercise volume and TUT per repetition (LaChance & Hortobagyi, 1994;Nobrega et al, 2018a). Recently, Nobrega et al (2018a) showed that the volume (e.g., number of repetitions or volume load (sets × repetitions × load)) is higher in SELF compared to CON. On the other hand, the TUT per repetition was higher in CON compared with SELF (2 s: 2 s vs. 1.5 s: 1.5 s, respectively).…”

“…Although to date no study has investigated the chronic effects of self-selected RD (SELF) with controlled RD (CON) on muscle strength and mass, a study from our laboratory analyzing the acute effects of RD manipulation on a RT session showed that a protocol with SELF (i.e., on average 1.5 s: 1.5 s) resulted in higher electromyography (EMG) amplitude compared with CON (Nobrega et al, 2018a). In fact, changes in RD seem to influence the amplitude of EMG, with shorter RDs resulting in larger EMG amplitudes (Sakamoto & Sinclair, 2012).…”

Implementing Eccentric Resistance Training—Part 1: A Brief Review of Existing Methods

“…Specifically, researchers have attempted to alter the time parameters to improve hypertrophy and strength through increased ECC muscle tension via increased muscle activation or by increasing the time under tension [76][77][78]. Evidence has been mixed on the effects of extended durations on these performance metrics with some studies showing positive outcomes [77,78], but most showing no favorable outcomes [72,73,[79][80][81][82][83].…”