with psychological determinants of physical activity such as fear-avoidance \[[@CIT0018]\], outcome expectations \[[@CIT0017],[@CIT0019],[@CIT0020]\] and anxiety/depressive states \[[@CIT0021]\]. Another important aspect of self-efficacy is that it is not general in nature but related to specific situations, and also temporary, task-related, and relatively easy to influence \[[@CIT0016]\]. One of several ways to measure self-efficacy is the Exercise Self-Efficacy Scale (ESES), a self-administered questionnaire developed in English by Dzewaltowski \[[@CIT0012]\], and adapted to Swedish (ESES-S) by Denison et al. \[[@CIT0022],[@CIT0023]\]. The ESES evaluates self-efficacy to perform exercise despite a number of common barriers. As the ESES was originally developed to assess self-efficacy in a general population \[[@CIT0012]\], one crucial issue is whether this scale suits the characteristics of different subpopulations \[[@CIT0024]\], such as people with RA. In addition, versions of the scale in different languages have to be assessed for measurement properties. Internal consistency and test--retest reliability have previously been reported with satisfactory results in other subpopulations for the ESES, in both the English \[[@CIT0012],[@CIT0025]\] and Swedish versions \[[@CIT0023]\]. However, to our knowledge the ESES-S has not previously been tested for reliability and validity in people with RA.

Aim {#s0002}
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The aim of the present study was to investigate aspects of reliability and validity of the ESES-S in an RA population.

Materials and methods {#s0003}
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Participants {#s0004}
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A convenience sample of 244 people with RA participating in the Physical Activity in RA (PARA) 2010 study was included \[[@CIT0026]\]. The inclusion criteria were: RA according to the American College of Rheumatology (ACR) criteria \[[@CIT0027]\], 18--75 years and independent in daily activities measured by Stanford Health Assessment Questionnaire Disability Index (HAQ) scores ≤2 \[[@CIT0026]\]