Association between intra and inter-limb strength asymmetry with sprint kinematics and force-velocity profile in youth team athletes

Background

Maximal force plays a pivotal role in enhancing performance across various dynamic sports, particularly in sprinting biomechanics. However, muscle strength asymmetry among major muscle groups like the hamstrings and quadriceps may hinder sprint performance and raise injury risks. This study examines how intra- and inter-limb strength asymmetry relates to sprint kinematics and the power-force–velocity profile in youth athletes.

Methods

Seventy-four youth athletes from football, volleyball, and handball completed two testing sessions, 48 h apart. Assessments included anthropometric measurements, sprint tests, and isokinetic dynamometer strength evaluations at 60°.s⁻1 and 180°.s⁻1. Sprint kinematics were analyzed using the Optojump Next system, and force–velocity profile variables were determined via Samozino’s method. Asymmetry analysis used a standard percentage difference equation.

Results

Weak to moderate correlations (r = −0.46 to 0.45) were found between strength asymmetry and sprint parameters, suggesting limited impact of asymmetry on sprint kinematics and kinetics. Although most participants showed asymmetry levels below the 15% threshold deemed functionally significant, outliers had asymmetry values up to 42%, indicating considerable variability.

Conclusions

Lower extremity strength asymmetry moderately affects sprint kinematics and force–velocity profiles in young team athletes, challenging traditional views. Further research is needed to explore the mechanisms between strength asymmetry and sprint performance, aiming to inform targeted training interventions that optimize performance and reduce injury risks in youth athletes.