Validity and reliability of the Spanish movement ability measure: an item response theory approach

ABSTRACT Background Assessment of movement capacity is fundamental in the field of physiotherapy to understand patient progress and the effectiveness of therapeutic interventions. The Movement Ability Measure (MAM) instrument is a self-reported questionnaire designed to assess self-perceived movement capacity. Objective To validate a Spanish version of the MAM instrument. Methods A two-part study was designed, based on guidelines for the cultural adaptation of patient-reported outcome measures: a phase for adaptation, involving 15 participants, and a phase for psychometric property analysis using Item Response Theory. The second phase included 205 subjects (49.9 ± 16.2 years, and 60.5% women). Structural validity was examined through the partial credit model. Reliability was estimated using the coefficient of reliability separation, test information function, and test-retest reliability (intraclass correlation coefficient) at one week. The association with the Physical Functioning Subscale was assessed using Spearman correlation coefficients. Movement capacity across different groups was compared using Wilcoxon – Mann – Whitney and Kruskal – Wallis tests. Results The Spanish version of the MAM instrument showed good fit indices, especially in the multidimensional model. The correlation with the Physical Functioning Subscale was 0.79 (p < .001), and the coefficient of reliability separation was 0.98. The intraclass correlation coefficient was 0.94 (95% CI 0.89–0.97). When analyzing differences between groups based on age, reported mobility issues, presence of chronic illness, and origin group, statistically significant differences were found according to prior hypotheses (p < .001). Conclusion The Spanish version of the MAM instrument is both reliable and valid for evaluating movement ability.