Acute post-activation performance responses to isometric and dynamic squat pre-loading with and without electromyostimulation in soccer players: a randomized crossover trial

Introduction Acute performance-enhancement strategies aimed at optimizing athletic performance have received increasing attention in sports science. Among these, post-activation performance enhancement (PAPE) and electromyostimulation (EMS) have emerged as promising approaches for enhancing short-term neuromuscular performance. This study compared the acute effects of dynamic and isometric squat-based PAPE protocols, performed with or without EMS, on physical performance and perceptual responses in amateur soccer players. Methods Twenty-two competitive male amateur soccer players (age: 19.7 ± 1.1 years) participated in this randomized crossover study. Following one-repetition maximum (1RM) assessment and familiarization sessions, participants completed five experimental conditions separated by 48 h: dynamic back squat (DC), maximal voluntary isometric contraction (MVIC), DC+EMS, MVIC+EMS, and EMS only. Performance outcomes were assessed pre- and post-conditioning for each experimental condition and included countermovement jump (CMJ), zig-zag agility (ZZ), and shooting speed (SS). Perceptual responses included the ratings of perceived exertion (RPE), the ratings of perceived discomfort (RPD), and Numeric Rating Scale (NRS) scores. Results Linear mixed-model analyses revealed significant time effects for CMJ ( p = 0.047), ZZ ( p = 0.015), and SS ( p = 0.033), while a significant main effect of condition was found only for SS ( p < 0.001). No significant condition x time interactions was observed (p > 0.05). Bonferroni-adjusted pairwise comparisons of estimated marginal means for SS indicated higher overall shooting speeds in the DC and DC + EMS conditions than in the MVIC and MVIC + EMS conditions (p < 0.05), with DC + EMS showing the highest estimated marginal mean. Regarding perceptual responses, linear mixed-model analyses revealed a statistically significant main effect of the intervention on RPE scores ( p = 0.006) and a highly significant main effect for NRS scores ( p < 0.001). In contrast, no statistically significant main effect of the intervention was observed on RPD scores, although a trend toward significance was noted ( p = 0.073). Discussion Overall, adding EMS to dynamic or isometric squat-based PAPE protocols did not confer additional acute performance benefits beyond the corresponding exercise-only protocols, while significantly altering perceptual load.