Effects of an Initial Muscle Strength Level on Sports Performance Changes in Collegiate Soccer Players

The purposes of this study were to investigate effects of partial block periodized strength training on physical performance and to examine relationships between initial muscle strength measured with isometric mid-thigh pull (IMTP) and performance changes after 7 weeks of strength training. Seventeen collegiate male soccer players participated. Initial muscle strength was determined using IMTP while physical performance included 10 m and 20 m sprints and static vertical jump with a polyvinyl chloride pipe (SJ0), 20 kg barbell (SJ20), and barbell loaded to 40 kg bar (SJ40). Performance testing was performed at three points: before first week (baseline), fourth week (T1), and seventh week (T2). Statistically small to moderate changes were found from baseline to T2 in peak power (PP; p < 0.001, ES = 0.49), net impulse (NI; p < 0.001, ES = 0.49), peak velocity (PV; p < 0.001, ES = 0.62), allometrically scaled PP (PPa; p < 0.001, ES = 0.62) in SJ20 and jump height (JH) in SJ40 (p < 0.001, ES = 0.36). Moderate to large correlations were found between isometric peak force and the changes from baseline to T2 in SJ20 PP (p = 0.04, r = -0.49), SJ20 PF (p = 0.03, r = -0.52), PPa (p = 0.04, r = -0.50), and SJ20 allometrically scaled peak force (p = 0.04, r = -0.49). Properly structured strength training maximizes task-specific physical performance. Initial muscle strength negatively affects the magnitudes of adaptations to physical performance.