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 ham-strings (PT-H), hamstrings/quadriceps (H/Q) ratio) was measured for the dominant and non-dominant leg at angular velocities of 60 degrees s-1and 240 degrees 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 degrees s-1only). 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 degrees s-1 and peak torque of the quadriceps at 240 degrees s-1 for the non-dominant leg (R2 = 19.6%; p <= 0.001) and only peak hamstring torque at 240 degrees s-1 for the dominant leg (R2 = 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.