RELIABILITY AND PRECISION OF ISOKINETIC STRENGTH AND MUSCULAR ENDURANCE FOR THE QUADRICEPS AND HAMSTRINGS

The importance of accurately reproducing isokinetic strength values is critical for the assessment of training induced changes in muscle fun ction. The purpose of this study was to determine the test re-test rel iability of the Biodex System 2 Isokinetic Dynamometer for concentric quadricep and hamstring strength and muscular endurance. Twenty-one he althy volunteers underwent isokinetic testing on 2 occasions separated by 7 days. Each subject performed 5 repetitions at 60 degrees/second followed by a muscular endurance test which consisted of 30 repetition s at 180 degrees/second. The results demonstrated high ICC values rang ing from r = 0.88 to r = 0.97 and r = 0.82 to r = 0.96 for variables m easured at 60 degrees/second and 180 degrees/second, respectively. SEM values were found to range from low to moderate, 4.8% to 11.6% and 5. 6% to 10.8%, at 60 and 180 degrees/second, respectively. ICC coefficie nts were found to be low, r = 0.52 to r = 0.74, and SEM values were fo und to be high, 9.8% to 20.8%, for the work fatigue index at 180 degre es/second. The results demonstrate that isokinetic values obtained at 60 and 180 degrees/second are highly reproducible with the Biodex Syst em 2 Dynamometer provided that adequate calibration, gravity correctio n and patient positioning is recorded and standardized. However, the w ork fatigue index as a measure of muscular endurance has not been show n to be reliable or precise. Changes in muscular strength over time sh ould be considered valid if these differences lie beyond the SEM value s reported in this study.