Psychometric evaluation of the index of self-regulation.

Index of Self-Regulation (ISR) is a nine-item scale designed primarily to measure individuals' level of self-regulation for physical activity. The aim of this study is to report psychometric characteristics of the ISR. The ISR scale was administered in a sample of 183 adult patients at 2 weeks following graduation from cardiac rehabilitation, 3 months following graduation, and 6 months following graduation. The internal consistency of the ISR was high at all three time points, with Cronbach's alphas of .81 to .96 across time points. The test-retest reliability was fairly high, with an overall coefficient of .73. There was evidence of concurrent validity of the ISR based on its moderately significant correlations with other theoretically relevant variables, including self-knowledge and motivational appraisal for physical activity. In conclusion, the ISR is a reliable and valid measure to assess the level of self-regulation in the maintenance of physical activity.