Menstrual cycle vs oral contraceptives: muscle protein response to resistance exercise
The Effect of Menstrual Cycle Phase and Oral Contraceptive Use on Muscle Protein Metabolism Post-Resistance Training
This trial will test whether natural menstrual cycle phases or taking oral contraceptives change how muscles build protein after resistance exercise in active women aged 18–40.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 20 (estimated) |
| Ages | 18 Years to 40 Years |
| Sex | Female |
| Sponsor | University of Toronto Academic / other |
| Locations | 1 site (Toronto, Ontario) |
| Trial ID | NCT07258576 on ClinicalTrials.gov |
What this trial studies
The trial compares muscle protein synthesis after a resistance exercise bout between women with natural menstrual cycles and women using monophasic or triphasic oral contraceptives. Participants are recreationally active women aged 18–40 with BMI 18.5–29.9 who resistance-train at least twice weekly and meet hormone-based inclusion criteria. The protocol uses a protein beverage and stable isotope tracers ([D5]phenylalanine and [13C]phenylalanine) to measure muscle protein turnover around exercise. Non-oral contraceptive participants must demonstrate progesterone sufficiency and OC users must have used their pill type for more than one year.
Who should consider this trial
Good fit: Recreationally active women 18–40 years old with BMI 18.5–29.9 who resistance-train at least twice weekly and either have regular menstrual cycles or have used monophasic/triphasic oral contraceptives for over one year.
Not a fit: Women with chronic diseases, obesity (BMI ≥30), hormonal IUDs (non-copper), current use of medications known to affect muscle protein synthesis, recent emergency contraception, or who cannot attend in-person lab visits are unlikely to benefit or be eligible.
Why it matters
Potential benefit: If successful, the findings could help personalize training and protein-intake recommendations for women using oral contraceptives or following natural cycles to improve muscle growth and recovery.
How similar studies have performed: Previous small physiological studies have examined sex hormones and muscle protein synthesis with mixed or inconsistent results, so this trial builds on limited prior evidence rather than a well-established consensus.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * Age: 18-40 years * BMI between 18.5-29.9 kg/m2 (non-obese) * Recreationally active (resistance train minimum twice a week) * Using monophasic or triphasic oral contraceptives for \>1 year (for oral contraceptive users) * Have regular menstrual cycles (21-35 days) for the past 3 months and discontinued any hormonal contraceptive use for at least 6 months (non-oral contraceptive users) * Must meet a progesterone sufficiency test (non-oral contraceptive users) Exclusion Criteria: * Mid-luteal progesterone levels \<16umol * Chronic disease diagnosis (cardiovascular, thyroid, diabetes) * Current or recent remission of cancer * Regular use of non-steroidal anti-inflammatory drugs (NSAIDs; except low-dose aspirin), anticoagulants * Use of prescription drugs that would impact muscle protein synthesis, e.g. Statins, Lithium, ADHD medication. * Insertion of intrauterine device (IUD) - exception: copper * Use of emergency contraception in the last 3 months (e.g. Plan B) * Severe food allergies (e.g. soy, nuts) * Smoking, use of performance enhancing drugs (growth hormones, testosterone)
Where this trial is running
Toronto, Ontario
- Goldring Center for High Performance Sport — Toronto, Ontario, Canada (Recruiting)
Study contacts
- Study coordinator: Daniel R Moore, PhD
- Email: dr.moore@utoronto.ca
- Phone: 4169464088
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.