Test-retest reliability of isokinetic muscle strength of the lower extremities in patients with stroke

Abstract

Objective: To investigate the test-retest reliability of isokinetic strength measurements of 3 muscle groups of the lower extremities in stroke patients. Design: Isokinetic strength tests of bilateral hip flexors, knee extensors, and ankle plantarflexors at 2 angular velocities, performed during 2 sessions scheduled 1 week apart for each subject. Setting: Outpatient rehabilitation clinic of a local hospital in Taiwan. Participants: Nine patients with mild spastic hemiparesis secondary to stroke and with poststroke onset time of at least 6 months. All subjects could communicate and voluntarily move the affected lower extremity. Interventions: Not applicable. Main Outcome Measures: The maximal peak torque, total work, and average power of the 3 muscle groups on the affected side examined during each test were quantified by using the normalization and the deficit methods. The normalization method divides the measured strength value by the patient's body weight, whereas the deficit method divides the difference between the strengths of the unaffected and affected extremities by the strength of the unaffected extremity. Results: The normalized strength measures for muscles on the affected side showed good to excellent test-retest reliability (intraclass correlation coefficient [ICC] range,.62-.94; P< 05), whereas the deficit strength measures did not always show good reliability (ICC range,.13-.91). The knee extensors and ankle plantarflexors, but not the hip flexors, on the affected side showed better test-retest reliability of isokinetic strength generated at faster velocity (ICC range,.73-.94) than that generated at slower velocity (ICC range,.62-.88). The normalized peak torque (ICC range,.76-.94) and total work (ICC range,.83-.91) were more reliable than the normalized average power (ICC range,.62-.90) for all 3 muscle groups on the affected side. Conclusions: Quantitative assessment of muscle strength of the affected lower extremity in patients with mild spastic hemiparesis secondary to stroke is feasible using isokinetic testing. However, the test-retest reliability of isokinetic strength measures is affected by the quantifying method, testing velocity, and strength measures. ? 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.