The acute effect of squat exercises performed at different depths on muscle activation and jump performance: a randomized crossover trial

BACKGROUND: This study examined the acute effects of different squat depths (partial, parallel, full) on lower extremity muscle activation and countermovement jump (CMJ) performance. METHODS: 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: Both mean and peak activation values of all muscles increased significantly with greater squat depth (p < 0.001). 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, a significant improvement between pre-test and post-test values was found only after the full squat condition (p = 0.011); however, the overall magnitude of change (ΔCMJ) did not show a significant difference among the three squat depths (p = 0.268). CONCLUSION: Increasing squat depth positively affects lower extremity muscle activation. While full squats provide the greatest neuromuscular stimulation and can serve as an effective stimulus for acute post-activation performance enhancement (PAPE), they should not be considered statistically superior to partial or parallel squats in terms of acute jump performance gains. TRIAL REGISTRATION: ClinicalTrials.gov, NCT07543237. Registered on 15/04/2026.