Kinetic asymmetries during running in male youth

Objectives: A possible injury risk factor is limb asymmetry, which may differ across maturation given the adult growth spurt. The aim of this study is to quantify the magnitude of asymmetry in a number of kinetic variables during a running task in male youth of different maturity status. Design: Quantitative observational laboratory study. Setting: Sports performance laboratory. Participants: Non-injured youth athletes in pre-, mid-, and post-pubescent status. Main outcome measures: Inter-limb leg asymmetries whilst sprinting on a non-motorized treadmill. Percent asymmetry was defined as: (Left leg-right leg)/right leg*100=%asymmetry. Results: Horizontal force presented limb asymmetries of 15.4, 14.8 and 14.7% for the pre-, mid- and post-PHV group respectively. Values for vertical force were higher (18.1, 20.2 and 20.8% respectively). Power asymmetries were 14.9, 15.8, and 15.5% respectively and work asymmetries were significant higher in pre-PHV participants (26.4%) compared to mid- (14.7%) and post-PHV (17.3%) participants. Conclusions: As the population in this study was characterized as non-injured, asymmetries of 15-20% appeared typical during a running task in developmental athletes.