OBJECTIVE: The unique foot morphology and distinctive functions facilitate complex tasks and strategies such as standing, walking, and running. In those weight-bearing activities, postural stability (PS) plays an important role. Correlations among foot type, PS, and other musculoskeletal problems that increase sport injury risk are known. However, long-term associations among the foot type, the PS, and body weight (BW) distribution are lacking. Thus, the purpose of this study was to longitudinally identify changes in foot morphology, PS, and symmetry in BW distribution during adolescence among elite male soccer players. METHODS: Thirty-five Czech elite male soccer players (age, 15.49 ± 0.61 years; BW, 64.11 ± 6.16 kg; body height, 174.62 ± 5.71 cm) underwent foot type, PS, and BW distribution measurements during 3 consecutive years (T1, T2, T3). The Chippaux-Smirak index (CSI), BW distribution, and centre of pressure (COP) displacement (total traveled way [TTW]) of each player for the preferred (PL) and non-preferred leg (NL) were acquired. Repeated-measures analysis of variance (RM ANOVA), Bonferroni´s post hoc tests, and partial eta-squared (ηp2) coefficient were used for investigating the effect of time on selected variables and effect size evaluation. RESULTS: Statistically significant effect of time on CSI values (PL: F2,68 = 5.08, p < 0.01, ηp2 = 0.13 and NL: F2,68 = 10.87, p < 0.01, ηp2 = 0.24) and COP displacement values (PL: F2,68 = 5.07, p <0.01, ηp2 = 0.13; NL: F2,68 = 3.53, p <0.05, ηp2 = 0.09) for both legs over 3-years period was identified. Furthermore, the Bonferroni´s post hoc analysis revealed a significant improvement of PS values in the PL (TTWT1 = 1617.11 ± 520.22 mm vs. TTWT2 = 1405.29 ± 462.76, p < 0.05; and between TTWT1 = 1617.11 ± 520.22 mm vs. TTWT3 = 1370.46 ± 373.94, p < 0.05). Only BW distribution parameter showed no significant differences, although slightly improved over time. CONCLUSIONS: We observed changes in foot typology, PS, and BW distribution in young elite male soccer players during 3 consecutive years. Results demonstrated that changes in PS and body weight distribution under the high-load sport conditions during adolescence may improve with aging, except for foot morphology. Therefore, foot morphology should be carefully monitored to minimize sport injury risk in professional young soccer players during adolescence. Further research is necessary to determine more clear associations between these parameters, soccer-related injuries, and sport performances.

Orthopedic Center Children's Hospital Boston Boston United States of America The Micheli Center for Sports Injury Prevention Waltham United States of America Department of Orthopaedic Surgery Harvard Medical School Boston United States of America

Sport Research Center Faculty of Physical Education and Sport Charles University Prague Czech Republic

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