Bilateral differences of isokinetic knee extensor strength are velocity- and task-dependent

Area of Science:

• Biomechanics
• Sports Science
• Human Movement Analysis

Background:

• Assessing interlimb strength balance is crucial for performance and injury prevention in athletes.
• Isokinetic dynamometry is commonly used to evaluate muscle strength and functional deficits.
• Previous research has not fully explored the concordance of bilateral strength differences across various movement types and velocities.

Purpose of the Study:

• To investigate the concordance of isokinetic bilateral strength differences in knee extensors.
• To compare strength differences between single-joint (knee extension) and multi-joint (leg press) tasks.
• To determine the influence of movement velocity on bilateral strength assessment.

Main Methods:

• One hundred nineteen male athletes performed isokinetic leg presses (0.1 m/s, 0.7 m/s) and knee extensions (60°/s, 180°/s).
• Bilateral differences and directed bilateral differences were calculated for all measurements.
• Bland-Altman plots and concordance correlations were used to analyze agreement between tests.

Main Results:

• Poor to fair concordance was found between leg press conditions and between single- and multi-joint tasks.
• Single-joint knee extensions showed moderate agreement.
• Bilateral strength differences were dependent on movement velocity and task type, with no clear pattern in magnitude or direction.

Conclusions:

• Isokinetic assessment of bilateral knee extensor strength is task- and velocity-dependent.
• No single isokinetic test can reliably assess interlimb strength balance.
• Performing multiple, varied isokinetic tests is recommended for a comprehensive evaluation of strength symmetry.