The goal of this clinical trial is to precise the impact of menstrual cycle and physical activity on the hamstrings muscle function in healthy active women. The main question it aims to answer is : is there a moment of the menstrual cycle when the muscle is better able to recover from a strenuous exercise ? Three appointments will be conducted to evaluate the hamstring muscles at difference moments of the menstrual cycle. Echographic and maximal force production measures will be done.

Researchers will compare these results with a group taking oral contraceptives.

Inclusion Criteria:

• Subject aged between 18 and 35 years.
• Subjects who practice at least 2 hours of sport per week with a competitive aim.
• Subject who has not presented any musculo-tendinous pathology to the hamstrings in the last 6 months.
• Subject with no musculoarticular pathology having a prolonged (more than 2 weeks) interruption of sports activities in the last 2 years.
• Subject with no muscular pain or pathology currently.
• Subject with no known cardiac disorders or family history that could present a risk known family history that could present a risk in case of intense physical effort.

physical exertion.

• Subjects not taking any medication, which in the opinion of the that, in the opinion of the coordinating investigator, may interfere with the evaluation of the study criteria.
• Subject able and willing to comply with the protocol and agreeing to give written informed consent.
• Subject affiliated or benefiting from a Social Security plan.

Menstrual cycle group:

• Subject whose last 3 menstrual cycles are of a regular duration (± 4 days maximum difference between 2 consecutive menstrual cycles).
• Subject whose last 3 menstrual cycles are of a duration between 24 and 32 days (including milestones).
• Absence of any contraceptive method likely to modulate the hormonal variations linked to the menstrual cycle.

hormonal variations related to the menstrual cycle, during the duration of the duration of the protocol and during the last 6 months after the participant's inclusion.

the participant. Mechanical contraception such as the diaphragm is permitted.

Oral contraceptive group:

- Taking oral contraception, 2nd generation monophasic pill estrogen-progestin pill (Optilova®, Optidril®, Leeloo®, Minidril®, Ludeal®, Zikiale®, Lovavulo®, Lovapharm®) for at least 6 months.

Exclusion Criteria:

• Subjects with a medical contraindication to intense physical activity.
• Subject with a positive pregnancy test result.
• Subject with a medical or surgical history deemed by the coordinating investigator as being incompatible with the study.
• Subjects under guardianship.
• Subjects in a period of exclusion from another study.
• Decision of the volunteer, whatever the reason.
• Adverse event or effect affecting the safety of the volunteer in the opinion of the coordinating investigator.
• Major deviation from the protocol.
• Illness or injury interfering with the normal course of the protocol.