Psychometric Properties of the Commitment to Exercise Scale in Inpatients With Anorexia Nervosa and Bulimia Nervosa.

OBJECTIVE

Compulsive exercise is a common behaviour among persons with eating disorders, particularly in those with anorexia nervosa (AN) and bulimia nervosa (BN). In the current study, we examined psychometric properties of a German version of the eight-item Commitment to Exercise Scale (CES) with a four-point scale response format.

METHOD: Data of N = 2424 persons with AN and BN who completed the CES among other measures as part of the routine diagnostic assessment at admission to and discharge from inpatient treatment were analysed based on a preregistered protocol (https://doi.org/10.17605/OSF.IO/Z2RYW).

RESULTS

The CES had high internal consistency and a one-factor structure with measurement invariance across age and diagnostic groups. Large correlations with other measures of compulsive exercise supported convergent validity and small-to-moderate correlations with other measures supported divergent validity. Scores on the CES were sensitive to change as they moderately decreased during inpatient treatment, with changes in compulsive exercise being larger in males and persons with AN that in females and persons with BN.

CONCLUSIONS

The CES has sound psychometric properties in persons with AN and BN. Given its brevity, it may be favoured over lengthier instruments for assessing compulsive exercise in research and clinical practice.