Introduction: Evaluating real-world arm use ("performance") is crucial in orthopedic rehabilitation; however, existing tools often measure only subjective difficulty. The Motor Activity Log (MAL) assesses real-world use but has not been validated in orthopedic populations. This study was conducted to examine the reliability and validity of the Japanese version of the MAL in patients with upper extremity orthopedic disorders. Materials and methods: In this cross-sectional study, 30 patients with upper extremity orthopedic disorders completed the Japanese version of the MAL, which comprises the amount of use (AOU) and quality of movement (QOM) scales. Reliability was assessed using Cronbach’s α for internal consistency, intraclass correlation coefficients (ICC) for test-retest reliability, and Bland-Altman analysis for systematic error. Construct validity was evaluated using Spearman’s rank correlation coefficients to analyze relationships with the QuickDASH (Quick Disabilities of the Arm, Shoulder, and Hand), the Visual Analog Scale (VAS) for pain, and grip strength. Results: Cronbach’s α was 0.96 for both scales of the MAL, indicating high internal consistency. Test-retest reliability was excellent (ICC > 0.99). Bland-Altman analysis revealed no fixed or proportional bias. Regarding validity, the results supported the hypothesized pattern of strong convergent validity with the QuickDASH (r = -0.87 to -0.83) and VAS (r = -0.64 to -0.51). Discriminant validity was supported by moderate correlations with grip strength (r = 0.50), indicating that the MAL captures a construct distinct from physical capacity. Conclusions: Our findings support the view that the Japanese version of the MAL has high reliability and validity for assessing real-world arm use in patients with orthopedic disorders. It effectively measures "performance," which is distinct from "capacity" or "subjective difficulty." This tool is clinically useful for identifying discrepancies between functional recovery and actual use, particularly in the presence of pain-induced protective behavior. Combining the MAL with existing tools, such as the QuickDASH, allows clinicians to evaluate whether functional recovery translates into real-world arm use, facilitating targeted rehabilitation strategies.
Sasagawa et al. (Sun,) studied this question.