Reproducibility of isokinetic peak torque assessments of the hip flexor and extensor muscles

Isokinetic assessment is currently the reference method for measuring dynamic muscle strength. We have sought to evaluate the reproducibility over time of isokinetic testing of the hip flexor (FI) and extensor (Ext) muscles and to establish whether there is a significant difference in peak torque (PT) between the left and right hips.

Ten adults were tested once a week for 3 weeks by the same investigator and according to the same protocol, with two velocities (60 degrees /s and 180 degrees /s) for the hip FI and Ext in concentric tests and one velocity (30 degrees /s) for the Ext only in eccentric tests. The reproducibility of the measured PT was analyzed by using the intraclass correlation coefficient (ICC) and a Bland and Altman plot. The difference in PT between the right and left hips was tested using Student's T test.

The ICC for the observed PT values revealed very good reproducibility (with a value of between 0.75 and 0.96) for the hip FI and Ext measurements (regardless of the body side, test velocity or contraction mode). We did not observe any significant PT differences between the right and left hips.

The isokinetic assessment of the concentric and eccentric PT values generated by the hip FI and Ext is highly reproducible. There is no difference between dominant and nondominant body sides, which enables the use of the contralateral limb as a reference.