The importance of accurately reproducing isokinetic strength values is critical for
the assessment of training induced changes in muscle function. The purpose of this
study was to determine the test re-test reliability of the Biodex System 2 Isokinetic
Dynamometer for concentric quadricep and hamstring strength and muscular endurance.
Twenty-one healthy 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 repetitions at 180 degrees/second.
The results demon-strated high ICC values ranging from r = 0.88 to r = 0.97 and r
= 0.82 to r = 0.96 for variables measured 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 coefficients
were found to be low, r = 0.52 to r = 0.74, and SEM values were found to be high,
9.8 % to 20.8 %, for the work fatigue index at 180 degrees/second. The results demonstrate
that isokinetic values obtained at 60 and 180 degrees/second are highly reproducible
with the Biodex System 2 Dynamometer provided that adequate calibration, gravity correction
and patient positioning is recorded and standardized. However, the work fatigue index
as a (measure of muscular endurance has not been shown to be reliable or precise.
Changes in muscular strength over time should be considered valid if these differences
lie beyond the SEM values reported in this study.
Key words
Isokinetic - reliability - endurance - precision - quadriceps - hamstrings
