Development and validity assessment of a Japanese version of the Exercise Adherence Rating Scale in participants with musculoskeletal disorders

BACKGROUND: Exercise adherence is important for achieving a long-term effect from musculoskeletal management. The Exercise Adherence Rating Scale (EARS), which was developed in 2017 as a patient reported outcome measure to assess exercise adherence in those with chronic low back pain in the UK, has demonstrated acceptable validity and reliability and is a robust measure of exercise adherence. This study aimed to undertake cross-cultural adaptation of the EARS into Japanese and investigate its structural validity in participants with musculoskeletal disorders. METHODS: The current study was composed of two phases, where a provisional Japanese version of the EARS was developed employing an international guideline for cross-cultural adaptation (Phase A), and structural validity was then evaluated using the Rasch analysis (Phase B). Participants with musculoskeletal disorders who have individualized home exercises prescribed by a physical therapist were recruited. RESULTS: In Phase A, the pilot testing was conducted twice because the initial testing detected some uncertainty revealed in comments from 17 participants (5 males and 12 females, 18–79 years of age) about which activities and exercises were supposed to be included. We therefore modified the draft by identifying a person who prescribed/recommended activities and exercises as per the Working Alliance Inventory. The second pilot testing using this draft recruited 30 participants (6 males and 24 females, 18–79 years of age), who provided no further comments, demonstrating the Japanese version of the EARS (EARS-J) had been successfully developed. In Phase B, data from 200 participants who completed the EARS-J (63 males and 127 females, mean ± SD of age = 53.6 ± 17.0) were analyzed using the Andrich's Rating Scale Model. Rasch statics indicated unidimensionality of the six items of the EARS-J. The Cronbach α was 0.77. Substantial ceiling effect (21.0%) was observed, with no floor effect (0.5%). CONCLUSIONS: A Japanese version of the EARS has been developed, which demonstrated acceptable structural validity with the evidence of unidimensionality in the Rasch analysis in Japanese people with musculoskeletal disorders who were prescribed individualized home exercises. However, there was a substantial ceiling effect and further studies are required to comprehensively establish validity and reliability of the EARS-J. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12955-021-01804-x.