Validation study of the Functional Assessment Scale for Acute Hamstring injuries in Spanish professional soccer players

To cross-culturally adapt and validate the Functional Assessment Scale for acute hamstring injury for professional Spanish-speaking soccer players. Clinical measurement study. Cross-cultural adaptation was conducted following international recommendations. Indicators of validity, reliability and responsiveness are provided. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale was administered to 165 participants: 45 professional soccer players with acute hamstring muscle injury diagnosis, 40 healthy subjects, 40 individuals at-risk for a hamstring muscle injury and 40 patients with injuries of the lower limb other than hamstring muscle injury. The Functional Assessment Scale for acute hamstring injury. Spanish version of the Quality of Life Short-Form 36 questionnaire (SF-36) and the Lower Limb Functional Index (LLFI). Cronbach’s alpha (internal consistency) for the Spanish version of the Functional Assessment Scale for acute hamstring injury scale was >0.8. The intraclass correlation coefficient using the two-way random model (ICC2,1) (test–retest) was 0.993 (95% confidence interval (CI): 0.991–0.995; P？<？0.05). In the exploratory factor analysis, a one-factor solution explained 85% of the variance. Subjects with hamstring muscle injury scored significantly lower than the other groups in the Spanish version of the Functional Assessment Scale for acute hamstring injury scale (P？<？0.001). The Spanish version of the Functional Assessment Scale for acute hamstring injury scale score within the hamstring muscle injury group showed moderate and significant correlations with SF-36 physical components (Spearman’s rs？>？0.6; P？<？0.001), and LLFI score at baseline (rs？=？0.42; P？<？0.01). The standard error of measurement (SEM) and minimum detectable change threshold (MDC95%) were 2.6 and 7.2 points, respectively. The responsiveness indicators have an effect size of 3.62, and the standardized response mean is 3.24. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale showed satisfactory psychometric properties. It can be considered a reliable and valid instrument to assess the functional impact of acute hamstring muscle injury in professional Spanish-speaking football players