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

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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; < 0.001, ES = 0.49), net impulse (NI; < 0.001, ES = 0.49), peak velocity (PV; < 0.001, ES = 0.62), allometrically scaled PP (PPa; < 0.001, ES = 0.62) in SJ20 and jump height (JH) in SJ40 ( < 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 ( = 0.04, = -0.49), SJ20 PF ( = 0.03, = -0.52), PPa ( = 0.04, = -0.50), and SJ20 allometrically scaled peak force ( = 0.04, = -0.49). Properly structured strength training maximizes task-specific physical performance. Initial muscle strength negatively affects the magnitudes of adaptations to physical performance.