The slow squat exercise using body weight (SQ) has training benefits in healthy individuals and may be applicable in rehabilitation settings. Including or excluding a pause phase during muscle exertion may provide greater flexibility; however, no studies have examined its effects on exercise performance or muscle activity. This study clarified the impact of a pause phase during SQ on the number of repetitions and the dynamics of muscle activity. A crossover trial included seven young adult male individuals performing SQs without a pause phase (CON; transition to the next repetition with slight knee flexion), and with a pause (FEA; with the knee fully extended). Concentric-eccentric movements lasted 3 s, with a 1-s pause, and continued until volitional exhaustion. The number of repetitions (NR) until exhaustion and integrated electromyography (EMG) of the rectus femoris and vastus lateralis during exercise were normalized to the %EMG obtained during the isometric maximal voluntary contraction of knee extension. The NR until exhaustion was approximately two-fold higher in the FEA group than in the CON group (p < 0.001). The %EMG of the rectus femoris for repetitions 1–40 was significantly lower in the FEA group than that in the CON group (p < 0.01). A strong positive correlation was observed between the rate of change in the NR until exhaustion and the rate of change in rectus femoris activity (r = 0.82, p < 0.05), suggesting that incorporating a pause phase during SQ alters rectus femoris activity during movement and may enhance exercise endurance.
Ogata et al. (Tue,) studied this question.