Objective: To investigate the relationship between performance-based tests, ratings of activity limitations, self-efficacy, and pain in fibromyalgia.
Setting: University hospital.
Participants: Sixty-nine women with fibromyalgia (mean age, 45+/-7.8y).
Interventions: Not applicable.
Main outcome measures: The patients completed 4 performance-based tests focusing on muscle power function and 3 unloaded arm movements. The patients rated their activity limitations by means of the subscales of physical function (PF) and pain on the Fibromyalgia Impact Questionnaire (FIQ), the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and the Arthritis Self-Efficacy Scale (ASES). Spearman correlation coefficient (rho) and multivariate regression analysis were conducted.
Results: The highest correlations were found between the 6-minute walk test (6MWT) (rho range, -.48 to .68) and the activity limitations and between hand grip strength (rho range, -.34 to .57) and the activity limitations. The regression analysis indicated that hand grip strength explained 25% of the variation in the SF-36 PF scale. The 6MWT plus endurance of the shoulder muscles explained 24% of the variation in the FIQ PF scale and the 6MWT plus active abduction of the shoulder explained 48% of the variation in the ASES function scale. Correlations between the performance-based tests and the activity limitations tended to be higher than those between performance and pain.
Conclusions: The majority of the performance-based tests and the patients' subjective ratings of activity limitations showed significant relationships. The 6MWT and hand grip strength, reflecting activity limitations in the SF-36, FIQ, and ASES, are recommended for use in clinical research and in the clinical examination when planning treatment for patients with fibromyalgia.