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.

Acknowledgments

The authors thank the participants involved in this study.

Declaration of interest: The authors report no declarations of interest.