Eccentric and concentric isokinetic knee flexion and extension: a reliability study using the Cybex 6000 dynamometer

Area of Science:

• Biomechanics
• Sports Medicine
• Rehabilitation Science

Background:

• Isokinetic dynamometry is crucial for evaluating muscle function.
• Assessing the reliability of specific devices like the Cybex 6000 is essential for accurate clinical and research applications.
• Understanding knee muscle performance is vital for injury prevention and rehabilitation.

Purpose of the Study:

• To evaluate the test-retest reliability of the Cybex 6000 isokinetic dynamometer.
• To assess the reliability of concentric and eccentric knee muscle performance measurements.
• To compare the reliability of different performance variables (peak torque, total work, average power) and testing speeds.

Main Methods:

• Thirty healthy subjects (18 male, 12 female) underwent isokinetic testing of knee flexor and extensor muscles.
• Testing was performed at 60°/s and 120°/s using a continuous concentric-eccentric protocol.
• Interclass correlation coefficient (ICC 2,1) was used to determine reliability (P < 0.05).

Main Results:

• High test-retest reliability was found for peak torque (ICC 0.82–0.91), total work (ICC 0.76–0.89), and average power (ICC 0.71–0.88).
• Reliability was significantly higher at 120°/s compared to 60°/s for all variables.
• Knee extensors and concentric contractions demonstrated greater reliability.

Conclusions:

• The Cybex 6000 is a reliable tool for measuring concentric and eccentric knee muscle performance.
• Clinicians and researchers should consider potential minor fluctuations in muscle performance measurements between tests.
• Higher testing speeds (120°/s) and concentric modes yield more reproducible results.