Grip strength in children: Test–retest reliability using Grippit

Abstract Aim: To examine the reliability of peak and sustained grip strength in children using the Grippit. We compared the reliability of one trial, the best and mean of three trials and the reliability within 6‐, 10‐ and 14‐year‐old groups. Design: Test–retest study. Methods: Grip strength with the Grippit instrument was evaluated at two test occasions in 58 children. Intraclass correlation coefficient 2.1 (ICC), standard error of measurement (SEM) also expressed as a percentage value (SEM%), coefficient of repeatability and coefficient of variation were calculated. Results: The test–retest reliability was good for both peak and sustained grip strength. The mean and best of three trials were equally reliable. Peak grip strength best of three trials, for example, was more reliable for the 6‐year‐olds (ICC 0.96, SEM% 6.3) and 14‐year‐olds (ICC 0.96, SEM% 5.2) compared to the 10‐year‐olds (ICC 0.78, SEM% 12.5). For peak grip strength in the whole sample, there was a systematic bias with better performance at the second measurement. Conclusion: Grip strength assessment in children with Grippit results in good relative and absolute reliability for peak and sustained grip strength. We recommend that three test trials are used. The mean of and the best of three trials are comparable.