Reliability, minimal detectable change and measurement errors in knee extension muscle strength measurement using a hand-held dynamometer in young children

[Purpose] Few studies have assessed the reliability of muscle strength measurement using a hand-held dynamometer, specifically in Japanese young children. This study aims to investigate the reliability, minimal detectable change and measurement error in knee extension muscle strength measurements in young children using a hand-held dynamometer. [Participants and Methods] The study participants comprised 36 kindergarten-enrolled children of 3–6 years age. An experienced physiotherapist measured their isometric knee extension strength. Appropriate orientation and practices were performed prior to measurement. The same physiotherapist took the muscle measurements twice; and the maximum value was used as the muscle strength value. The measurements were repeated at intervals of approximately 30 min to verify reproducibility. [Results] The initial isometric knee extension strength was 10.6 ± 3.3 kgf and the Intra-class correlation coefficient (1,1) was 0.765. The standard error of measurement was 1.6 kgf and the minimal detectable change was 4.4 kgf. No significant systematic errors were observed. [Conclusion] Isometric knee extension strength measurement using a hand-held dynamometer in young children has good reliability with a low risk of systematic errors.