Effects of the Menstrual Cycle and Oral Contraceptive Use on Health and Performance in Athletes

Recruiting now

Conditions studied: Menstrual Cycle, Oral Contraceptive Use, Athlete

In brief

A review of the sports medicine literature reveals a clear underrepresentation of female athletes in research. In the current era of precision medicine, increasing attention has been directed toward the regulatory roles of estrogen and progesterone in athletic performance and health optimization. Regular fluctuations in estrogen and progesterone across menstrual cycle phases (i.e., early follicular, late follicular, and mid-luteal phases) may influence strength performance, hydration status, body composition, and energy balance. However, few studies have examined these outcomes using hormonal confirmation of menstrual cycle phases. Monophasic oral contraceptive use also represents a highly relevant hormonal condition among female athletes, as exogenous hormones suppress endogenous ovarian fluctuations and create distinct hormonal profiles across active pill-consumption and withdrawal phases. Nevertheless, the influence of oral contraceptive phases on strength-related outcomes, hydration markers, body water regulation, body composition, and energy balance remains insufficiently characterized, particularly in comparison with naturally menstruating athletes. In response to these gaps, this longitudinal observational study primarily aims to examine variations in strength-related outcomes across three distinct menstrual cycle phases (early follicular, late follicular, and mid-luteal) in eumenorrheic athletes. Secondary objectives include: (i) conducting within- and between-group comparisons of hydration status, energy balance, and strength outcomes (maximal, endurance, and explosive torque) in naturally menstruating athletes and oral contraceptive users; (ii) testing the reliability of methods used to assess body water, energy expenditure, and body composition across the menstrual cycle; (iii) exploring associations between energy availability, resting energy expenditure, and sex hormone concentrations across menstrual cycle phases; and (iv) testing, validating, and proposing methodological recommendations for the use of bioelectrical impedance analysis in tracking fluid-related changes across hormonal phases. To achieve these goals, the study will use a longitudinal observational design involving 40 female athletes, including 24 naturally menstruating athletes and 16 oral contraceptive users. Naturally menstruating athletes will be assessed during the early follicular, late follicular, and mid-luteal phases of the menstrual cycle, while oral contraceptive users will be assessed across pill-consumption and withdrawal phases. Measurements will be conducted across the three menstrual cycle phases and across oral contraceptive use phases, and will include: i) maximal voluntary isometric strength assessed using handgrip dynamometry, bench press, and leg press; ii) serum estrogen and progesterone; iii) body water and its compartments, and water turnover by dilution techniques; iv) hydration status by plasma osmolality, sodium, and vasopressin; v) energy balance by doubly labeled water and body composition changes; vi) resting energy expenditure by indirect calorimetry.

Key facts

Study ID

NCT07591818

Run by

Faculdade de Motricidade Humana

People needed

40

Starts

2026-04-01

Expected to finish

2028-06-01

Last updated by the study team

2026-05-18

Who can join

Age: 18 and older, up to 30. Sex: female. Healthy volunteers: accepted.

You may qualify if…

• Cisgender female individuals (biologically female, not undergoing gender-transition therapy)
• Age between 18 and 30 years;
• Classified as at least Tier 2 athletes;
• Minimum of 1 year of federated sports participation;
• Menarche occurred at least 3 years prior to enrollment;
• Additional inclusion criteria for the natural menstrual cycle group:
• Menstrual cycle length between 21 and 35 days with at least nine consecutive cycles in the previous year;
• Confirmed ovulatory cycle (luteinizing hormone surge and progesterone >16 nmol/L);
• Additional inclusion criteria for the oral contraceptive group:
• Use of combined monophasic oral contraceptives with a 21-day regimen;
• Use of the same oral contraceptive for at least 3 months prior to enrollment;

You may not qualify if…

• Pregnancy or child birth within the previous 12 months;
• Active smoking;
• Diagnosis of metabolic, cardiovascular, or respiratory disease:
• Use of continuous or extended-cycle oral contraceptives.

Where it is running

• Faculdade de Motricidade Humana — Cruz Quebrada, Oeiras, Portugal (enrolling)

Full record on ClinicalTrials.gov

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