United States: The fitness movement “cycle syncing” promotes that women obtain best muscle growth outcomes through workout scheduling based upon their menstrual cycle phases. Recent McMaster University findings debunk the idea that strength training results rely on cyclic timing during the menstrual period.
No Link Between Cycle Phases and Muscle Growth
Social media influencers and fitness apps have promoted the idea that women should modify their exercise routines based on hormonal fluctuations. The theory claims that weightlifting during menstruation leads to greater muscle gains due to higher estrogen levels, as reported by HealthDay.
However, lead researcher Lauren Colenso-Semple, a doctoral candidate at McMaster University, challenges this belief.
“Our findings conflict with the popular notion that there is some kind of hormonal advantage to performing different exercises in each phase,” she said. “We saw no differences, regardless of cycle timing.”
Examining the Science
The study followed twelve healthy young women with regular menstrual cycles. Researchers tracked their muscle protein synthesis during two key phases:
Follicular phase – when estrogen is at its highest
Luteal phase – when progesterone levels peak
Participants consumed a tracer molecule to measure muscle protein levels while performing strength training exercises. The results showed that weightlifting led to muscle growth, but the menstrual cycle phase had no impact on the body’s response.
The Myth of the “Perfect” Cycle
Interestingly, researchers found that only about 12% of women follow the textbook 28-day cycle with ovulation on day 14. This means that many cycle-syncing recommendations may not align with a woman’s actual hormone fluctuations.
What This Means for Women Who Train
Senior investigator Stuart Phillips, research chair in skeletal muscle health at McMaster, emphasized that women should prioritize how they feel rather than their menstrual cycle when planning workouts, as reported by HealthDay.
“Our work shows that women who want to lift weights and recondition their muscles should feel free to do so in any phase of their cycle,” Phillips said. “There is no physiological difference in response to the exercise. It is important to tailor your training to how you feel.”