The Acute Effect of Squat Exercises Performed at Different Depths on Muscle Activation and Jump Performance: A Randomized Crossover Trial

This study examined the acute effects of different squat depths (partial, parallel, full) on lower extremity muscle activation and jump performance (countermovement jump - CMJ). Fourteen healthy sports science students participated in this randomized crossover study. Participants performed three sets of squats at their 5-repetition maximum (5RM) load across three different depths. Surface electromyography (SEMG) was recorded from the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) muscles during each set, while CMJ performance was assessed before and after the squat protocols. Results indicated that both mean and peak activation values of all muscles increased significantly with greater squat depth. The highest activation levels in the RF and BF muscles occurred during the full squat, whereas VL activation peaked during both the full and parallel squat conditions. Regarding CMJ performance, no decline was observed after any condition; however, a significant improvement between pre- and post-test values was found only after the full-squat condition. Increasing squat depth positively influences muscle activation and jump performance, and performing full squats in training may enhance neuromuscular stimulation and promote post-activation performance enhancement (PAPE).