How ankle joint mobility changes in young soccer players of different ages: a time series analysis.

Soccer practice can induce a limitation of ankle joint mobility (AJM) that is a dreaded risk factor for injury and other negative consequences over time. Objective: The aim of this study was to investigate the role of muscle strength (MS) in the definition of AJM of young soccer players (YSP). Methods: In 160 YSP, mean age 12.0±2.5 yrs, body mass index (BMI) 18.8±2,9 Kg/m 2 , and in 61 subjects who practiced basketball, volleyball and martial arts matched for age, BMI and sex, the AJM in both plantar flexion and dorsiflexion and the handgrip strength (HGS) were evaluated by inclinometer and Jamar hydraulic hand dynamometer respectively. Time series analysis was applied to assess the association between muscle strength and AJM in the soccer group versus the non-soccer group, depending on the age of the members of the two groups. Results: The AJM value observed in YSP was significantly lower compared to that of the controls (p<0.001). The HGS values found in YSP were similar to those of non-soccer players. Multivariate analysis showed that AJM resulted significantly associated with sport practiced (p<0.001). In the soccer group correlation analysis showed an inverse correlation between HGS and ankle dorsiflexion (p=0.005). Decomposition of time series analysis showed that in YSP after 13.3 years of age AJM decreases maintaining an inverse relationship with HGS (p<0.001). Conclusions: In YSP the ankle joint mobility is inversely correlated to muscle strength. The trend of this inverse relationship provides an indication of the important role of muscle activity in the development of ankle stiffness as well as indications for the monitoring and prevention of the same limited AJM