Mechanisms Underlying Pathological Exercise in Women

Pathological exercise (PE) is a common feature of individuals with eating disorders (ED) and

represents a key maintaining factor of eating pathology. However, little is known about

underlying mechanisms that maintain PE and whether these mechanisms are influenced by the

occurrence of PE in the context of an ED. The present study tested hypotheses that women with

PE would 1) experience exercise as more reinforcing, 2) show greater cortisol reactivity in

response to exercise, and 3) that greater cortisol reactivity in response to exercise would predict

greater increases in positive affect following exercise. Participants (N=64 women total; n=16 PE

with ED, n=16 PE Only, n=16 ED Only, n=16 Control) completed a computerized progressive

ratio (PR) task to earn running time on a treadmill as a measure of the reinforcing value of

exercise. HPA-axis response to acute exercise was measured through salivary cortisol and

changes in affect were measured by a self-report questionnaire. Participants provided four saliva

samples and self-report ratings directly prior to and 0-, 20-, and 40- minutes after running for 30

minutes on a treadmill at 75% maximum heart rate. Results indicated that women with PE had

significantly higher reinforcing value of exercise (pto exercise (pexercise-induced changes in affect in the full sample. Cortisol reactivity significantly predicted

breakpoint on the PR task (pevidence that women with PE may experience exercise as more rewarding than normal

exercisers, which may be attributable to dysregulations in underlying biological mechanisms that

influence its reinforcing value. Given limitations of the current study, future studies should use

ecological momentary assessment to better understand factors driving associations between PE,

reward, and dysregulations in HPA-axis activity in participants' natural environment.