Test-retest reliability of isokinetic hip adductor and flexor muscle strength

Objective: To determine the test-retest reliability of eccentric hip flexor and adductor peak torque and endurance using a Cybex Norm isokinetic dynam ometer and to evaluate muscle soreness after exercise as a result of the te sting procedure. Design: Prospective test-retest reliability study. Participants: A total of 19 male volunteers (21-43 years old). Intervention: Tests included hip flexor and adductor peak torque strength m easured at 60 degrees/s (concentric and eccentric) and endurance measuremen ts (total work done over 20 continuous concentric/eccentric contractions at 150 degrees/s). Subjects were tested on three occasions at 1-week interval s. Main Outcome Measures: Repeated measures analysis of variance was performed for all dependent variables including the subject's dominant and nondomina nt side among the three test sessions. Intraclass correlation coefficients (ICCs) were calculated to compare the data between sessions. In addition, s imple linear repression analysis was completed to determine the relationshi p between session measurements for all measures with ICC > 0.75. Results: The main findings of this study are that eccentric peak hip adduct or torque was reliably measured on a Cybex Norm isokinetic dynamometer usin g a continuous eccentric/concentric cycle protocol at a speed of 60 degrees /s (ICC > 0.84). Peak concentric adductor torque and peak eccentric and con centric hip flexor torque were less reliable using the same protocol (ICC < 0.67). Endurance measurements, using total work done over 20 repetitions, were not reliable for hip flexor and adductor muscle groups using a continu ous eccentric/concentric cycle protocol at a speed of 150 degrees/s (ICC < 0.55). Posttest muscle soreness was found to be of significant concern with such a protocol. Conclusion: The results from this test-retest reliability study confirm the reliability of eccentric peak hip adductor torque measurements for use cli nically and in future research. In addition, the need to assess posttest mu scle soreness after isokinetic muscle testing is confirmed.