Reproducibility of lower strength tests using a new portable dynamometer; measurement comparisons with a non-portable dynamometer

Objectives: Hand-held dynamometers have been used to assess lower limb muscle strength. However, they have been reported to have various reliability and be dependent on the strength of the participant and that of the examiner. A new way to assess lower limb muscle strength using a portable load cell is being introduced in assessing knee extensors, hip abductors, hip external rotators and combined hip abductors and external rotators (‘clam’ position). The study aimed to identify the test-retest reliability, intra-rater reliability and validity of the new assessment method. Method: Twenty healthy controls took part in this study which took place in a physiology lab and performed four isometric strength tests on the portable dynamometer at two times. The first time the tests were also performed in an isokinetic dynamometer to assess validity. Results: The new assessment method was found have high reliability (knee extension ICC=0.99; hip abduction ICC=0.94; hip external rotation=0.97; ‘clam’=0.95) and high validity (knee extension ICC=0.99; hip abduction ICC=0.98; hip external rotation=0.90; ‘clam’=0.98) when compared to a gold standard isokinetic dynamometer. Conclusion: The new method is reliable and valid. It is more time-consuming than a hand-held dynamometer however it provides precise results without being dependent on the examiner