Abstract

According to the CDC, in 2018, approximately 22% of women between the ages of 15-49 use hormonal birth control (Daniels, 2018). Many women use hormonal birth controls, but the effects of birth control on certain aspects of life, like exercise and endurance, are understudied and require more research. This study investigates how ethinyl estradiol and levonorgestrel, both synthetic steroids found in hormonal birth control, affects aerobic endurance in female rats. Three experimental groups and one control were assigned: ethinyl estradiol (n=9), levonorgestrel (n=9), ethinyl estradiol and levonorgestrel (n=10), and control (vehicle only) (n=9). The rats were trained on a treadmill, performed a treadmill endurance test at the beginning for twelve days and then once again after 27 days of endurance training. Then a weight-loaded forced swim test was performed at the at the end of the study. The rats were also weighed weekly for 5 weeks. The group that was administered only levonorgestrel had significantly higher weights than the other groups following treatment. There were no significant differences time spent swimming between the groups during the forced weighted swim test. There was not enough data to analyze the treadmill endurance tests. I concluded that ethinyl estradiol and levonorgestrel may have no effect on endurance. However, there are limitations to this pilot study. Using information from this pilot study, a new experiment can be designed to produce meaningful results. I describe factors that should be considered for such a study in the discussion.

Advisor

Lynn, Sharon

Department

Biology

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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Available for download on Tuesday, July 16, 2030

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© Copyright 2025 Kennedy R. Beursken