Self-determined motivation and physical activity in patients with rheumatoid arthritis: a cross-sectional study.

Objective: To identify factors associated with two self-reported measures of physical activity (PA) in patients with rheumatoid arthritis (RA).

Method: Hospital outpatients with RA from central Norway filled in questionnaires about symptoms, psychological factors, and PA. Outcomes were two alternative self-reported measures of PA: (i) fulfilling the aerobic PA recommendations of ≥ 150 min/week at moderate intensity or ≥ 75 min/week at vigorous intensity; or (ii) being in the PA maintenance stage of the Stages of Exercise Behaviour Change framework. Logistic regression was applied to identify factors associated with PA. Step 1 included the independent variables sex, age, and smoking habits. Step 2a added self-reported function, joint pain during the past 6 months, and fatigue to Step 1. Step 2b added Exercise Self-Efficacy and the Relative Autonomy Index (RAI), calculated from the Behavioural Regulation in Exercise Questionnaire-2, to Step 1. Step 3 included all the mentioned independent variables. Steps 1-3 were analysed for each PA measure.

Results: In total, 227 patients participated. The RAI had a statistically significant positive association with being physically active according to both PA definitions. Joint pain had a significant negative association with meeting the aerobic PA recommendations but was not associated with being in the PA maintenance stage.

Conclusion: The degree of self-determined motivation was the most consistent variable associated with self-reported PA behaviour. Joint pain was associated with one of the two PA measures. Motivation and joint pain may be useful targets for intervention in clinical practice to improve PA engagement among patients with RA.