Acute and Short-Term Neuromuscular and Perceptual Responses to Isometric vs. Dynamic Strength Training in Youth...

This study aimed to compare the short-term neuromuscular impairments resulting from a single session of isometric and dynamic strength training in youth soccer players. Twenty-one male youth soccer players (aged 16.8 ± 0.9 years) participated in this counterbalanced crossover trial, and were randomly assigned to a training sequence, starting with either a dynamic (3 sets of 4 repetitions of squats and deadlifts at 75% and 80% of 1RM, respectively) or an isometric training session (3 sets of 4 maximal 4-second repetitions of isometric squats and mid-thigh pulls) with protocols standardized for the number of exercises, sets, repetitions, and recovery intervals. A one-week washout period was allowed before participants switched training conditions. A repeated-measures ANOVA was used to assess the differences in countermovement jump (CMJ) height, bar velocity during half-squats, and perceived soreness and fatigue across different time points (baseline, 30 minutes, and 24 hours post-exercise). CMJ height was significantly greater in the isometric condition 30 minutes post-exercise compared to the dynamic condition (d = 0.71; p < .001). Additionally, the isometric condition exhibited significantly higher bar velocity 24 hours post-exercise (d = 0.69; p < .001). While no significant differences were detected in perceived soreness between groups at any time point, perceived fatigue was significantly reduced in the isometric condition at the 24-hour mark (d = 0.70; p < .05). These findings suggest that dynamic strength training may impair neuromuscular function to a greater extent than isometric training.