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A Journal on Internal Medicine and Pharmacology

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Gazzetta Medica Italiana Archivio per le Scienze Mediche 2012 June;171(3):253-61

language: English

Seasonal variation in the isokinetic strength of youth soccer players: effects of age and dominance

Forbes H., Siegler J. C.

Department of Sport, Health and Exercise Science, University of Hull, Don Building, Cottingham Road, UK


Aim. The aim of this study was to examine seasonal variation in isokinetic strength and muscle balance in young soccer players aged 11-15.
Methods. Subjects were grouped according to their chronological age (U12-U15;n=47) and isokinetic assessment of peak torque (PT) took place (after familiarization and a standardized warm-up) three times during the course of one competitive season. The variables of interest were peak torque divided by body-weight (PTBW) of the quadriceps and hamstring muscles, and balance of the same muscles using conventional (CHQ) and functional (FHQ) ratios. We collected concentric PTBW data for the quadriceps group (CQ), and concentric and eccentric PTBW data for the hamstring group (CH, EH) at 60°s-1. To investigate intra-seasonal changes a mixed model repeated measures ANOVA with Sidak correction was applied for CQ, CH, EH, CHQ, FHQ. Higher order interaction effects were noted along with main effects for time, age group and dominance.
Results. In relation to time, a mid season drop in PTBW was noted for CQ, CH and EH (range: 1.1-7.7%;p<0.05). In relation to age-group, the oldest age group consistently displayed greater concentric PTBW than the youngest (CQ, CH;p<0.05). Interestingly, this finding was not present when considering EH, CHQ or FHQ. Finally, in relation to dominance, it was apparent that the younger age groups had a stronger dominant leg during CH contraction (p<0.01).
Conclusion. Coaches, clinicians and trainers should not consider strength and muscle balance as consistent variables across the course of a competitive season. This may have implications for conditioning and injury risk and prevention strategies.

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