Relative reinforcing value of exercise in inpatients with anorexia nervosa: model development and pilot data.

OBJECTIVE

This study sought to quantify, among patients hospitalized for the treatment of anorexia nervosa (AN), the reinforcing value of exercise, defined as the amount of work a patient would expend for the opportunity to exercise.

METHOD: Sixteen inpatients with AN performed a computerized progressive ratio (PR) task for the opportunity to exercise for either 15 or 30 min, or a monetary voucher. Exercise "breakpoint" was calculated and compared with clinical measures.

RESULTS

Patients performed an average of 1134.4 (+/-751.2) button presses for exercise. Exercise breakpoint was significantly correlated with the Beck Depression Inventory (BDI; r = .728, p = .001), and there was a trend toward a correlation with the Commitment to Exercise Scale (CES; Davis, 1993; r = .490, p = .054).

CONCLUSION

Results support the feasibility and potential utility of this novel application of the PR task to quantify the reinforcing value of exercise in AN. The association between exercise and depression is consistent with some prior studies in AN. The trend toward an association with CES scores suggests that breakpoint captures an aspect of the motivation for exercise in this population.