Utility and reliability of non‐invasive muscle function tests in high‐fat‐fed mice

New Findings What is the central question of this study? Non‐invasive muscle function tests have not been validated for use in the study of muscle performance in high‐fat‐fed mice. What is the main finding and its importance? This study shows that grip strength, hang wire and four‐limb hanging tests are able to discriminate the muscle performance between chow‐fed and high‐fat‐fed mice at different time points, with grip strength being reliable after 5, 10 and 20 weeks of dietary intervention. Non‐invasive tests are commonly used for assessing muscle function in animal models. The value of these tests in obesity, a condition where muscle strength is reduced, is unclear. We investigated the utility of three non‐invasive muscle function tests, namely grip strength (GS), hang wire (HW) and four‐limb hanging (FLH), in C57BL/6 mice fed chow (chow group, n = 48) or a high‐fat diet (HFD group, n = 48) for 20 weeks. Muscle function tests were performed at 5, 10 and 20 weeks. After 10 and 20 weeks, HFD mice had significantly reduced GS (in newtons; mean ± SD: 10 weeks chow, 1.89 ± 0.1 and HFD, 1.79 ± 0.1; 20 weeks chow, 1.99 ± 0.1 and HFD, 1.75 ± 0.1), FLH [in seconds per gram body weight; median (interquartile range): 10 weeks chow, 2552 (1337–4964) and HFD, 1230 (749–1994); 20 weeks chow, 2048 (765–3864) and HFD, 1036 (717–1855)] and HW reaches [n; median (interquartile range): 10 weeks chow, 4 (2–5) and HFD, 2 (1–3); 20 weeks chow, 3 (1–5) and HFD, 1 (0–2)] and higher falls [n; median (interquartile range): 10 weeks chow, 0 (0–2) and HFD, 3 (1–7); 20 weeks chow, 1 (0–4) and HFD, 8 (5–10)]. Grip strength was reliable in both dietary groups [intraclass correlation coefficient (ICC) = 0.5–0.8; P