Psychometric evaluation of the exercise self-regulatory efficacy scale using objective measures of physical...

Physical activity (PA) promotion is an essential component of managing chronic obstructive pulmonary disease (COPD). Exercise self-efficacy is a primary indicator of exercise engagement. The Exercise Self-Regulatory Efficacy scale (Ex-SRES) was developed and validated in persons with COPD recruited at pulmonary rehabilitation programs who self-reported exercise behaviors. Our study evaluates its psychometric properties using objective assessments of PA and exercise capacity.

Secondary analyses were performed on baseline assessments of U.S. Veterans with COPD who participated in two PA intervention studies (N = 210; age M = 69 ± 8; 97 % male; 91.9 % White). The Ex-SRES asked how confident participants felt they could exercise 3X/week for 20 min given 16 barriers. The Omron HJ-720 or Fitbit Zip pedometer assessed daily step counts for 7-10 days and the 6-min walk test (6 MWT) assessed exercise capacity. Breathlessness was assessed with the Modified Medical Research Council Dyspnea Scale (mMRC). The St. George Respiratory Questionnaire (SGRQ) assessed health-related quality of life; participants self-reported confidence and motivation for exercising regularly. Exploratory factor analysis (EFA) assessed the underlying factor structure of the Ex-SRES and internal consistency reliability. Convergent validity was evaluated through correlations with objective and subjective measures.

EFA resulted in a one-factor structure accounting for 58.28 % of the common variance. The Ex-SRES demonstrated convergent-type validity: daily step counts (ρ = .17), 6 MWT distance (ρ = .22), mMRC (ρ = -.15), SGRQ (ρ = -.24), motivation (ρ = .42), and confidence (ρ = .58) (p's < .05) and internal consistency reliability (Cronbach's α = .95) CONCLUSION: Objective measures of PA and exercise capacity confirm the psychometric properties of the Ex-SRES.