RESUMO
BACKGROUND: Exercise and physical activity are an evidence-based practice for chronic pain. Health professionals need instruments to assess self-efficacy for this practice taking into account the specific barriers of patients with these health problems. PURPOSE: To develop and test the psychometric properties of a new self-efficacy scale for physical activity and walking exercise in patients with fibromyalgia. DESIGN: A cross-sectional and prospective study was conducted in a Spanish Fibromyalgia Unit. Two hundred and eleven new patients signed the informed consent and participated in the study. All of them were women, referred to by either Primary or Specialized Health Care. In addition to the new scale, they filled out several self-reported and validated instruments to collect the data present in this study. RESULTS: Exploratory factor analysis showed a three-factor model (GFI = .99; RMSR = .06) that explained 74.2% of the total variance. They assessed how confident patients felt about walking quickly in both 30- and 60-minute sessions, (Factor I: 10 items; α = .97), to perform daily physical activities (Factor II: 10 items; α = .93) and to undertake moderate physical activity (Factor III: 5 items; α = .95). The total score of the scale and the three-factor scores showed good criterion validity and adequate validity based on the relationships with other constructs. CONCLUSIONS: The scale showed adequate psychometric properties and can be a useful tool to help health professionals monitor patients' self-efficacy perception and customize both physical activity and walking exercise intervention goals and their implementation.