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

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.