The Effect of Menstrual Cycle Phase and Oral Contraceptive Use on Muscle Protein Metabolism Post-Resistance Training

What this Trial Is About

Researchers are investigating how menstrual cycle phases and the use of oral contraceptives affect muscle protein synthesis after resistance exercise in females aged 18 to 40 years. This study aims to improve understanding of protein metabolism influenced by female sex hormones such as estrogen and progesterone, which have often led to exclusion of females in past research due to assumed variability. The findings will help develop better training and nutrition advice tailored for females. Participants will be randomly assigned to one of four groups representing different menstrual or contraceptive phases: mid-luteal phase, early follicular phase, active pill phase, or placebo pill phase. They will consume protein beverages enriched with stable isotope tracers ([D5]phenylalanine and [13C]phenylalanine) over an 8-hour period to measure muscle and whole-body protein synthesis. The study includes resistance exercise sessions and precise timing related to menstrual or contraceptive cycles. During the trial, participants will undergo tests including muscle protein synthesis measurement over 8 hours and whole-body protein synthesis over 4 hours. Researchers will monitor progesterone levels and dietary intake and evaluate the effects of resistance training combined with protein consumption. The study includes safety checks and assessments related to hormonal status, with participation lasting throughout the assigned menstrual or contraceptive phase timing.

Menstrual Cycle vs. Oral Contraceptives: Effects on Muscle Protein Metabolism After Resistance Exercise