Reliability of isokinetic knee strength measurements in children: A systematic review and meta-analysis

Measuring muscle strength using isokinetic dynamometry allows evaluating and comparing normal and sick children, establishing recovery and rehabilitation goals, and quantitatively monitoring the course of a disease and the response to treatment. The purpose of this study was to carry out a systematic review and meta-analysis focusing on studies that examined the test-retest reliability of isokinetic knee strength measurements in children. This study is important because isokinetic dynamometry is the gold standard for evaluating muscle strength and it allows comparing muscle performance in children. The databases used were PubMed, Web of Science Scopus, and Embase (up to July 26, 2019). Only studies published in English were included in this review. All studies focused on the reliability of isokinetic knees in healthy children or those with cerebral palsy applied to dynamic contractions (concentric or eccentric) and provided measures of strength, reproducibility, ICC, peak torque, or SEM. We found a total of 143 abstracts and examined 94 articles to determine if they met the inclusion criteria. Finally, 10 articles were included in the systematic review and five studies (96 subjects) formed the meta-analysis sample, all of which focused on the reliability of isokinetic knees in the concentric mode. The CAT and QAREL scales were used to assess the quality of the included studies. The meta-analysis revealed high intra-class correlation coefficients (ICC) (0.84; p < 0.001; n = 96 subjects) in the flexion and excellent intra-class correlation coefficients (ICC 0.90; p < 0.001; n = 96 subjects) in the extension. Isokinetic dynamometry could be indicated as a method for measuring muscle strength training in children. However, the reviewed studies suggest some methodological issues in isokinetic tests, such as the rest days between testing and retesting, using the same speeds, protocols, and evaluators, and the performance of the subjects, so more research is required.