Reliability of an upper limb isokinetic evaluation in healthy individuals.

BACKGROUND

Muscle strength is a key functionality indicator and can be objectively assessed using isokinetic dynamometry (IKD). However, IKD evaluation of the upper limb remains clinically challenging as in research settings.

OBJECTIVE

To evaluate the test-retest reliability of IKD measurements for the shoulder, elbow, forearm, and wrist at different speeds, as well as for isometric handgrip strength.

METHODS

Isokinetic strength and isometric handgrip assessments were performed using the Biodex System 4 Pro™ and the Jamar™ dynamometer. Participants were tested twice with a 7-day interval. The speeds tested were 60°/s and 120°/s in concentric mode. Reliability analysis was performed using the Intraclass Correlation Index. Spearman's Correlation Coefficient (p ≤ 0.05) analyzed the correlation between handgrip devices.

RESULTS

Thirty-three healthy participants were tested. Peak torque and isometric handgrip strength demonstrated excellent reliability (ICC: 0.87-0.98) at both speeds. The standard error of measurement ranged from 0.56 to 8.6, and the minimum detectable change from 1.5 to 23.8. Significant laterality differences were observed at 120°/s for shoulder adduction, internal and external rotation, elbow flexion and extension, and wrist extension. Significant speed-related differences were found in some movements, with higher mean peak torque at 60°/s. The Spearman coefficient indicated a strong correlation between Jamar™ and Biodex™ handgrip measurements for both sides.

CONCLUSION

Isokinetic and isometric assessments using the Biodex System 4 Pro™ are highly reproducible for the tested positions and speeds. Additionally, the Jamar™ and Biodex™ handgrip devices can be used interchangeably when measurement units are standardized.