The relevance of using isokinetic measures to evaluate strength

Abstract

Isokinetic testing is often used to evaluate the effect of different types of interventions and also to interpret whether an individual is ready to return to physical activity. However, limited research exists concerning the suitability of evaluating the effect of isotonic training using isokinetic testing. The aim with this study was to assess the relation between the development of force during isokinetic and isotonic concentric maximal contractions. Fifty subjects (24 women and 26 men) performed maximal concentric isokinetic and isotonic elbow flexion. The isokinetic tests were performed in an isokinetic dynamometer and the isotonic tests in a pulley apparatus. The relationship between the isokinetic values (peak value and mean force value) and the isotonic values (1RM) was modeled by linear regression analysis. There was a significant linear correlation between both the isokinetic values and the isotonic value that explained 89% (peak) and 88% (mean) of the variation. From the linear regression analysis, two different formulas were derived to estimate the prediction of the isokinetic values. The significant relation between isokinetic and isotonic measures means that it may be possible to evaluate the effects of isotonic training by using an isokinetic dynamometer. However, there was a large variation around the predicted isokinetic values that has to be considered. It is important to point out that the results of this study are applicable only on healthy young men and women with similar strength as our subjects.

Key words::

• Isotonic
• muscle testing
• one repetition maximum
• regression analysis

Acknowledgements

The authors would like to thank Monica Edström, Anna Engerström, Magnus Kling, Kerstin Sandberg and Niklas Strömqvist for valuable assistance with data collection.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.