Strength And Functional Asymmetries In Elite Soccer Players

PURPOSE: The purpose of the study was to investigate the level, relationships, and differences between neuromuscular, isokinetic strength, and jump and running asymmetries in elite soccer players. METHODS: Elite male soccer players from the Czech highest division (n = 76, age = 24.3 ± 5.1 years) were tested in the following parameters: postural stability (PS), isokinetic strength of knee extensors (QQ) and flexors (HH), isometric bilateral strength of hip adductors (ADD) and abductors (ABD), vertical ground reaction force (VGRF) differences in counter movement jump-free arms (CMJFA), counter movement jump (CMJ), squat jump (SJ), drop jump (DJ) tests and running asymmetries ((Impact to Peak Force (IPF), Active Peak Force (APF), Force Impulse (FI), Loading Rate (LR), Push Off Rate (PoF), Time to Impact Peak (TtP)). One-way ANOVA, Pearson’s coefficient (r), coefficient of determination (R2) were calculated for data analyses. RESULTS: The magnitude of asymmetries varied by less than 5% for (CMJFA, SJ, ABD, IPF, APF, FI, PoF), from 5 to 10% for (CMJ, QQ, HH, ADD, LR, TtP) and over 10% for (PS, DJ). Results have shown significant differences between means of assessed asymmetries (F11,299 = 11.01, p < .01). Post-hoc test revealed significantly higher asymmetries in VGRF in DJ (14.28 ± 11.25%, CI95 = 11.71-16.85%), and PS (14.61 ± 9.94%, CI95 = 12.33-16.88%) to all other parameters p < .01). Asymmetries in isokinetic testing (QQ, HH) were significantly higher than running asymmetries (IPF, APF, FI, LR, PoF). Higher asymmetries were detected in ADD (5.23 ± 4.54%, CI95 = 4.20-6.27%) compared to APF (1.59 ± 1.64%, CI95 = 1.22-1.97%) and FI (1.33 ± 1.46%, CI95 = 1.00-1.66%). Thirteen significant correlations (p < .05, r = .24 - .68, R2 = .06 - .46) have been found. Significant (p < .05), but low correlation was between SJ vs. APF (r = .32) and DJ vs. IPF (r = .31). APF significantly correlated with FI (r = .64) and IPF with TtP (r = 0.50). CONCLUSIONS: The results revealed differences in magnitude and relationships between strength, power, and running asymmetries, which may have been caused by specific adaptations to impose training demands for elite soccer players. The constant and uncompensated loading in elite soccer players who engage in extended sessions of soccer practice may lead to strength asymmetry and imbalances in muscle tissue over time. Research has been supported by Cooperatio FTVS UK, B&R Medicine