For decades, researchers excluded females from resistance training research, often because of concerns about how endogenous ovarian hormones might influence adaptations. Premenopausal female physiology is unique because ovarian hormone concentrations fluctuate throughout the menstrual cycle. In particular, estrogen concentrations typically peak during the late follicular phase before ovulation, while progesterone concentrations peak during the mid-luteal phase after ovulation. Menstrual cycle phase-based training (MCPBT) emerged partly from animal model-derived research suggesting that estrogen may regulate repair and remodeling, followed by preliminary human research concluding that females could optimize adaptations more effectively by focusing training during the follicular phase rather than the luteal phase.
This concept of MCPBT has since become popularized on social media, where it is often referred to as “cycle syncing.” The premise is appealing: if estrogen and progesterone influence skeletal muscle adaptations, perhaps concentrating resistance training during these hormonal environments could optimize the adaptive responses. In particular, emphasizing training volume during the ostensible ‘anabolic’ follicular phase, when estrogen rises while progesterone remains relatively low, has been proposed to optimize muscle strength and hypertrophy.
An important caveat, however, is that most studies investigating the influence of MCPBT have lacked the methodological rigor required for proper phase identification, thereby failing to confirm the hormonal milieu in question. In addition, the menstrual cycle varies substantially within and between individuals. This variability highlights the need for researchers to use rigorous methods to establish menstrual cycle phase when examining phase-specific physiological or performance outcomes, particularly when those findings inform broader conclusions or practical recommendations.
In our recent study, published in Medicine & Science in Sports & Exercise®, we set out to do just that. Twenty-four young, untrained, eumenorrheic females completed a unilateral resistance training intervention in which each leg was assigned to one of four conditions. The intervention consisted of unilateral leg press and knee extensions performed to volitional failure with progressive overload throughout to maintain an 8-12 repetition range.
The critical factor in this intervention was how we distributed training across the menstrual cycle. One condition was a high-volume follicular phase, using a 5:1 (20 weekly sets versus four weekly sets for the quadriceps) distribution of follicular-to-luteal phase-based training sessions. Another emphasized the luteal phase using an opposite 1:5 follicular-to-luteal distribution. A third training condition used consistent training with a 3:3 (12 sets of quadriceps weekly) approach regardless of menstrual phase, while a non-training condition served as a control. Importantly, we used best practices for phase identification, including blood sampling, urinary luteinizing hormone testing to predict ovulation, and self-reported calendar tracking. This design allowed us to test whether MCPBT or “cycle syncing” produced greater adaptations than consistent training alone.
We found that all resistance training strategies increased muscle hypertrophy and strength compared with the control, but emphasizing training during either menstrual phase did not provide any advantage over consistent training. In other words, females can achieve robust adaptations in hypertrophy and strength regardless of menstrual cycle phase.
These findings, of course, are not an argument that ovarian hormones and the menstrual cycle are unimportant to skeletal muscle physiology. Estrogen and progesterone have important biological actions, but their primary purpose is reproduction, not skeletal muscle growth.
Of course, context matters and menstrual cycle symptoms are real. Cramps, pain, bloating, and psychological symptoms can affect training and should be acknowledged when programming for female athletes and trainees. Resistance training should always be adjusted for individual needs, and coaches, practitioners, and trainees can use autoregulation and menstrual cycle-informed strategies to accommodate symptoms and individual preferences. However, the science does not support making pre-planned changes to resistance training based on menstrual cycle phase or anticipated hormonal fluctuations. Rather, resistance training adaptations are driven by consistent training, sufficient effort, and progressive overload, not by aligning training with a particular menstrual cycle phase.
Derrick W. Van Every, PhD, is a postdoctoral fellow in the Protein Metabolism Research Lab at McMaster University (Hamilton, ON, Canada). His research focuses on the internal and external variables that drive resistance training adaptations. Derrick and his wife, Erica, own their own gym, South Kent Barbell, in Ontario, Canada. In addition to being a competitive natural bodybuilder and powerlifter, Derrick also works as an online coach for Calgary Barbell, working with strength and physique athletes.
Alysha C. D’Souza, PhD, is the director of research at Jeff Nippard Muscle Lab (Oakville, ON, Canada). Her research focuses on understanding resistance training practices and how exercise, nutrition, and hormonal factors interact to influence skeletal muscle adaptation. She completed her PhD in Kinesiology at McMaster University (Hamilton, ON, Canada), where she studied female exercise physiology and skeletal muscle protein metabolism. Alysha also has extensive applied experience in strength and conditioning and personal training, working with recreational and university athletes and mentoring developing coaches.
