Effect of endurance exercise on ovulation in the rat

Robert T. Chatterton*, Linda Hrycyk, Robert C. Hickson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


This study was designed to evaluate individual variation in ovarian responses to exercise. Rats ran on a treadmill (15% incline) at a rate of 26 nrmin−1for 90 min every day for 14-21 d; control rats were placed on a stationary treadmill for the same period of time. Based on daily vaginal cytology, 9 of 17 exercising rats had abnormal (>5 d) estrous cycles in the first cycle of training compared to only 2 of 19 controls. Throughout the training period, the length of estrous cycles of 8 of the 17 exercising rats were relatively unaffected; the mean length of completed cycles was 5.1 ± 0.4 (SE) d. However, of those thought to have ovulated based on vaginal cytology, fewer exercising than control rats had new corpora lutea on their ovaries. In exercising rats acyclic periods of up to 21 d were associated with serum progesterone levels similar to those of the diestrus phase of the estrous cycle (mean, 29 ± 4 SE nmo1.1−1). We conclude that treadmill running extends the period of progesterone secretion, delaying ovulation in a susceptible population of rats, and that vaginal cornification may not be an accurate indication of ovulation in these animals.

Original languageEnglish (US)
Pages (from-to)1509-1515
Number of pages7
JournalMedicine and science in sports and exercise
Issue number11
StatePublished - Nov 1995

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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