How the menstrual cycle and birth control affect strength and performance in athletes

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This observational study examines how hormonal fluctuations across menstrual cycle phases and monophasic oral contraceptive use relate to performance-related outcomes in trained female athletes. Hormonal phase confirmation will be used to categorize natural cycle groups, with separate comparisons for those on combined oral contraceptives. Participants are healthy, cisgender women aged 18–30 who participate at least at Tier 2 level and have at least one year of federated sport experience. The research aims to clarify how estrogen and progesterone variations may impact muscle strength, fluid balance, body composition, and energy expenditure in real-world athletic settings.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* 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;

Exclusion Criteria:

* 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's running

• Faculdade de Motricidade Humana
  Cruz Quebrada, Oeiras, Portugal Recruiting

Study contacts

• Principal investigator: Analiza M. Silva, PhD — Exercise and Health Laboratory, CIPER, Faculdade Motricidade Humana, Universidade de Lisboa
• Study coordinator: Flávio Jerónimo
• Email: flaviovjeronimo@gmail.com
• Phone: +351 910 928 710

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.