Effect of low dose oral contraceptives on exercise performance

Area of Science:

• Exercise Physiology
• Reproductive Endocrinology
• Sports Science

Background:

• Hormonal fluctuations during the menstrual cycle can influence physiological responses.
• Oral contraceptives (OCs) alter endogenous hormone levels, potentially affecting exercise capacity.
• Understanding these effects is crucial for female athletes' training and performance.

Purpose of the Study:

• To investigate the impact of menstrual cycle phase on exercise performance.
• To determine if a low-dose oral contraceptive affects exercise performance in women.
• To compare performance variability in women versus men.

Main Methods:

• Maximal treadmill tests (assessing VO2 max) and endurance runs were conducted.
• Men (n=15) served as controls to establish performance variability.
• Women (n=10) were tested in both follicular and luteal phases, then assigned to placebo or low-dose OC (norethindrone/ethinyl estradiol) for 21 days, with repeat testing.

Main Results:

• No significant differences in VO2 max, total test time, or breathing frequency were observed between menstrual cycle phases (follicular vs. luteal).
• Exercise performance metrics remained consistent during OC treatment (weeks 1 vs. 3).
• No significant differences in performance changes were found between men and women.

Conclusions:

• Menstrual cycle phase does not adversely affect maximal or endurance exercise performance.
• Low-dose oral contraceptives containing 1 mg norethindrone and 35 mcg ethinyl estradiol do not impair exercise performance.
• These findings suggest stable exercise capacity in women regardless of cycle phase or this specific OC regimen.