title: Correlation between the 8-repetition maximum test and isokinetic dynamometry in the measurement of muscle strength of the knee extensors: A concurrent validity study.
abstract: The 8-repetition maximum test has the potential to be a feasible, cost-effective method of measuring muscle strength for clinicians. The purpose of this study was to investigate the concurrent validity of the 8-repetition maximum test in the measurement of muscle strength by comparing the 8-repetition maximum test to the gold standard of isokinetic dynamometry. Thirty participants (15 males and 15 females, mean age = 23.2 years [standard deviation = 1.0]) underwent 8-repetition maximum testing and isokinetic dynamometry testing of the knee extensors (at 60, 120, and 240 degrees per second) on two separate sessions with 2-3 days between each mode of testing. Linear regression was used to assess the validity by comparing the findings between 8-repetition maximum testing and isokinetic dynamometry testing. Significant correlations were found between the 8-repetition maximum and isokinetic dynamometry peak torque at each testing velocity (r  =  0.71-0.85). The highest correlations were between the 8-repetition maximum and isokinetic dynamometry peak torques at 60 (r  =  0.85) and 120 (r  =  0.85) degrees per second. The findings of this study provide supportive evidence for the use of 8-repetition maximum testing as a valid, alternative method for measuring muscle strength.
authors.affiliation: Department of Physical Therapy, University of Central Arkansas, Conway, AR, USA. dtaylor@uca.edu
authors.forename: J David
authors.initials: JD
authors.lastname: Taylor
authors.forename: James P
authors.initials: JP
authors.lastname: Fletcher
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D016014:Linear Models; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D010808:Physical Examination / Q000295:instrumentation*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D055815:Young Adult