[Construction and validation of a self-efficacy scale for physical activity].

Background: The estimation by standardized tests on belief in personal capacity to practice regular physical activity (self-efficacy for physical activity) allows us to make predictions about the actual practice of this behavior. We do not have measuring instruments suitable for this purpose, therefore, we propose to construct and validate a scale to determine levels of self-efficacy of adult users of the Primary Health Care Services for regular physical activity.

Methods: Phases: 1) Develop and review the scale by expert judges. 2) A pilot study. 3) Determination of reliability and validity of the test. The sample was 388 adult users (18-65 years) of health centres from the province of Seville selected by cluster sampling (health centres) and quotas (town size, age and sex). Concurrent validity was found by the International Physical Activity Questionnaire (IPAQ) and discriminant validity by Beck Depression Inventory (BDI).

Results: The results reported adequate content validity and high reliability (Cronbach Alpha > 0,9 in all factors and β = 0,96). Exploratory factor analysis showed three factors explaining 52,569% of the variance. The scale was sensitive to activity levels assessed by the IPAQ (F (1)= 4.131; p <0.05) and negatively correlated with BDI (r = -0,127; p <0,05).

Conclusions: The psychometric properties of the scale are appropriate for measuring the efficacy of adult users of Health Services to practice regular physical activity.