The relationships between knee extensors/ flexors strength and balance control in elite male soccer players

BACKGROUND: Strength and balance are important factors for soccer players to be successful. This study’s aim was to determine the relationship between lower-limb muscle strength and balance control in elite male soccer players (n = 77). METHODS: Concentric isokinetic strength (peak torque of quadriceps (PT-Q) and hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio) was measured for the dominant and non-dominant leg at angular velocities of 60°s(−1)and 240°s(−1), as well as the total work for extensors (TW-Q) and flexors (TW-H) for both legs (at an angular velocity of 240°s(−1)only). Balance score (BAL score) was used for unilateral assessment of balance control using a Delos Postural System Test measurement tool. Hierarchical multiple regression analyses were performed to predict balance control using isokinetic knee strength performance for dominant and non-dominant legs. RESULTS: Final modelling included peak torque of hamstrings at 240°s(−1) and peak torque of the quadriceps at 240°s(−1) for the non-dominant leg (R(2) = 19.6%; p ≤ 0.001) and only peak hamstring torque at 240°s(−1) for the dominant leg (R(2) = 11.3%; p = 0.003) as significant predictors of balance score. CONCLUSION: Findings indicate that balance control is widely influenced by peak hamstring torque and peak quadriceps torque at high angular velocity particularly in the non-dominant leg i.e., the supporting leg in soccer players.