Physical activity and cortisol in anorexia nervosa.

Elevated physical activity is commonly observed among patients with Anorexia Nervosa (AN) and can manifest in several forms. While elevated physical activity may play a key role in the pathophysiology of this disorder, much remains unknown about it, including the relationship among its various manifestations, and their underlying mechanism(s). The purposes of the current study were to (1) quantify locomotor activity in inpatients with AN using an accelerometer, (2) determine the association between locomotor activity and exercise history and (3) determine the association between urinary cortisol and physical activity. Thirty-six women hospitalized with AN wore activity armbands for 48 h during the first 2 weeks of hospitalization, collected 24-h urine to measure cortisol, and completed rating forms. Activity counts varied more than four-fold among individuals but were consistent within individuals over the 2 monitoring days (p<0.001). Averaged 24-h activity counts were positively correlated with pre-hospitalization attitude towards exercise as measured by the Commitment to Exercise Scale (CES; p=0.032). Forty-two percent of women reported "high" exercise in the 3 months before hospitalization; compared to non-high-exercising patients, these women demonstrated a higher CES score (p<0.001) and a trend toward greater activity counts (p=0.059). Urinary cortisol was positively associated with activity counts (p=0.044) and CES score (p=0.018). These data suggest that some women with AN have a higher "drive" for physical activity that persists into early hospitalization. HPA axis abnormalities may be associated with this state.