Reliability and validity of the measurement of interdigital muscle thickness using a caliper gauge.

[Purpose] The measurement of muscle mass and thickness to improve preventive care for older adults in community and clinical settings has recently gained attention. Several studies have focused on the thickness of large muscles, such as the trunk and lower limb muscles. However, studies investigating hand muscle atrophy, which hampers daily occupations, are lacking. Therefore, there is a need to measure intrinsic muscle atrophy. This study aimed to investigate the reliability and validity of interdigital muscle thickness measurements using a caliper gauge. [Participants and Methods] This study included 41 healthy young participants. The interdigital muscle thickness was measured in two limb positions with muscle relaxation and contraction using a caliper gauge. Reliability and validity were assessed using the intraclass correlation coefficient and between the interdigital muscle thickness results and other relevant scales. [Results] The results showed high inter- and intra-rater reliability. Additionally, a significant moderate correlation was observed between the interdigital muscle thickness and the other tests regarding criterion-related validity. [Conclusion] Measuring the interdigital muscle thickness using a caliper gauge is a reliable way to evaluate intrinsic muscle thickness. Muscle atrophy between the thumb and index finger is commonly observed in clinical practice. Therefore, measuring muscle atrophy during interdigital muscle thickness or observing finger muscle atrophy may provide useful information in rehabilitation settings.