METHODS: A total of 181 young male athletes were recruited and categorized according to sport specialization (soccer or athletics) and age categories (U15, U17 or U19). Isokinetic strength was measured as peak muscle torque (PT), normalized to body mass, for the knee extensors (PT RESULTS: Significantly higher values of bilateral asymmetry (BA) of PT CONCLUSION: Soccer players displayed increased isokinetic strength and more balanced BA compared to the athletics group. Physiotherapists and strength coaches should focus on younger age groups, especially U15, due to the higher incidence of BA and lower relative strength regardless of specialization.