Share this article on:


Dart, L1; DiMarco, N M.1; Sanborn, C FACSM1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S33
A-15P Free Communication/Poster Obesity

1Texas Woman's University, Denton, TX and Texas Christian University, Ft. Worth, TX

(Sponsor: charlotte sanborn, FACSM)

The prevalence of menstrual disorders in the exercising female continues to be a major concern. Reproductive function is altered more frequently in women who exercise strenuously and maintain stringent weight goals. Similar patterns of ovulatory dysfunction due to exercise training have also been reported in laboratory rats.

Back to Top | Article Outline


The purpose of this study was to examine age-related patterns of ad libitum intake, voluntary exercise, and energy availability in young ovulating female rats.

Back to Top | Article Outline


Diet intake, body weight (BW), estrous cycling, and voluntary running distance was determined in 12 female Sprague Dawley rats during a 14-week trial. To assess the relative availability of energy (kcal/gm BW), differences in energy intake versus expenditure were determined. Energy intake was calculated at 3.8 kcal/gm diet consumed, and total energy expenditure was based on both the maintenance energy requirement (ME) of laboratory rats (112 kcal/BWkg 0.75/day), and the derived cost of energy expended by wheel running (5.024 kcal/kg/km).

Back to Top | Article Outline


A positive correlation between energy intake and expenditure was shown in rats, with greater energy expended due to growth and/or increased wheel running compensated by greater caloric intake (p < 0.001). An age-related (34 to 129 days) inverse relationship was noted between animal growth and relative energy intake (0.466 ± 0.01 to 0.258 ± 0.01 kcal/gm BW), expenditure (0.237 ± 0.00 to 0.200 ± 0.00 kcal/gm BW), and availability (0.229 ± 0.01 to 0.058 ± 0.00 kcal/gm BW), with a mean BW increase of 97% and a 75% decrease in available kcal/gm BW (p < 0.001). Regardless of growth-related decreasing trends in available energy or greater energy expended due to running distances, rats' continued with normal estrous cycling.

Back to Top | Article Outline


Results suggest that voluntary exercise does not adversely impact estrous cycling in the young ad lib-fed rat. In this study, greater energy expenditure was compensated with greater energy intake, allowing for greater energy availability to maintain the caloric cost of estrous cycling. Supported by Texas Food and Fiber Commission and Human Nutrition Research.

©2003The American College of Sports Medicine