The post-activation performance enhancement of sub-maximal load back squat with varied range of motion and intra-set fatigue on jump height in trained males

BACKGROUND: Post-activation performance enhancement (PAPE) is a strategy in sports science that improves athletic performance through preconditioning muscle activity. This study investigates the acute effects of sub-maximal load back squats with different ranges of motion (ROM) and intra-set fatigue on countermovement jump (CMJ) height. METHODS: This study employed a counterbalanced, repeated-measures experimental design to investigate the acute effects of sub-maximal load back squat with varied ROM and intra-set fatigue on CMJ height in trained males. A total of 12 resistance-trained athletes participated in a single-set protocol intervention comprising 4 conditioning activities (CAs): (i) deep squats with proximity-to-failure (SDP); (ii) deep squats to failure (SDF); (iii) half squats with proximity-to-failure (SHP); and (iv) half squats to failure (SHF). CMJ height was measured before the CAs and at 4, 8, and 12 minutes post-intervention, while mean velocity was continuously monitored during the CAs. RESULTS: No significant differences were observed in initial mean velocity across conditioning activities (F = 1.10, ηp² = 0.07, p = 0.36). Final repetition mean velocity differed significantly across conditions (F = 6.67, ηp² = 0.31, p < 0.01), with lower velocities and a greater number of repetitions observed in the failure conditions compared with the proximity-to-failure conditions (p < 0.01). A significant condition × time interaction was found for CMJ height (F = 2.231, ηp² = 0.13, p = 0.02). CMJ height increased at 4 minutes post-CA in the SDP and SHP conditions (p < 0.01 and p = 0.03, respectively), while increases occurred at 8 minutes post-CA in the SDF and SHF conditions (p = 0.03 and p < 0.01, respectively). A significant between-group effect was also observed (F = 3.949, ηp² = 0.21, p = 0.01). No between-group differences were present at 4 minutes post-CA (p = 0.24), but significant differences emerged at 8 and 12 minutes post-CA (both p < 0.01). CONCLUSION: Both proximity-to-failure and repetitions-to-failure protocols performed at 87% 1RM effectively enhanced CMJ performance. However, peak performance occurred earlier following the proximity-to-failure protocols, and half squats elicited greater enhancement effects than deep squats. These findings suggest that 3 repetitions of the half squat at 87% 1RM may represent a time-efficient strategy for inducing PAPE when explosive performance is required shortly before competition or training.