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What science supports cycle-syncing workouts?

The concept of aligning workouts with menstrual cycles, often referred to as cycle-syncing workouts, has been gaining attention. However, the scientific understanding of this approach remains limited.

Hormones and the different phases of the menstrual cycle significantly influence fitness and strength. However, individuals with menstrual cycles have been inadequately represented in performance-based research. A small fraction of studies focus on female athletes, and even fewer consider the impact of the menstrual cycle on athletic performance. For instance, between 2014 and 2020, only 6% of scientific papers published in six sports and exercise journals focused solely on female athletes.

Competitive athletes have been the primary advocates for recognizing the connection between menstrual cycles and physical performance. For example, the UK's West Brom women's football team changed their uniform from white to navy due to concerns about visible menstrual leakage affecting their focus. Emma Pallant-Browne stood up for her period staining on her competition day during her race when media outlets had criticized it as not being a "flattering photo". High-profile athletes like Serena Williams have also shared their experiences with menstrual-related issues, such as debilitating migraines.

Understanding the relationship between energy, activity levels, and menstrual cycles is not just relevant for athletes, but for all individuals with menstrual cycles. This understanding begins with familiarizing oneself with their own cycle, which can be influenced by factors such as diet, activity level, health conditions, and stress. The menstrual cycle consists of two main phases: the follicular stage (from the start of your period until ovulation) and the luteal phase (from ovulation until your next period starts). The hormones progesterone and estrogen, which guide the ovarian cycle, influence changes in the uterus, such as period volume and flow.

The menstrual cycle is not a rigid process and varies from person to person. Even among individuals with fairly predictable periods, ovulation doesn't occur on the exact same day for every cycle. Understanding your cycle is best achieved by tracking your period and noting the different experiences you have throughout your cycle.

The question of whether to rest or train during specific phases of the menstrual cycle is complex. Current research suggests some potential links between the cycle and physical performance, but the evidence is not strong enough to recommend systematic changes to training routines. Given the variability in cycles and hormones, and the nascent state of the science, an individualized approach that feels best for your body is recommended.

Research indicates that exercise performance might be slightly reduced in the early follicular phase compared to other menstrual cycle phases. However, these slight changes in strength or speed are likely to be noticeable only to elite or competitive athletes, not to those who exercise regularly for health and well-being. As science continues to explore the connections between hormones and exercise, we are learning more about how estrogen and progesterone influence muscles and energy levels.

Estrogen, for example, can influence the body's ability to use stored energy, activate parts of the brain responsible for decreasing inhibition, and provide some anti-inflammatory protection to muscles. There is some evidence that the late follicular phase and the mid-luteal phase may positively influence aspects of fitness, mainly due to the presence of higher estrogen levels. Phases of your cycle with lower estrogen levels may result in reduced energy and performance, but the current evidence is limited.

Muscles may be more vulnerable to injury or strain when estrogen is low, offering less protection against inflammation. As estrogen levels dip at the end of the luteal phase, some people may experience premenstrual symptoms, such as fluid retention, mood changes, and pain that can impact overall energy and physical outputs.

It is recommended to listen to your body during all phases of your cycle to develop an individualized routine for physical activity. Rest days are essential in any training program. They may be best taken during the early follicular phase while also incorporating pre- and post-workout stretching into your routine. This doesn't mean you should entirely skip training in this phase; you might want to consider lighter activity and more recovery time during the first week of your period.

Menopause and hormonal contraceptives can also impact strength training and exercise performance. People with cycles spend one-third of their lives in a lower sex hormone state, known as menopause. Lower levels of sex hormones could result in decreased strength and slower muscle building, which is why it is so important to stay physically active as you age to maintain your strength and balance.

Hormonal oral contraceptive pills can also play a role in muscle building and strength because they reduce your ovaries’ hormone levels by blocking the signals from the pituitary that signal ovulation. This could result in a possible (and slight) decrease in exercise performance. However, the difference is insignificant and should not influence decisions on contraceptive use. There is some evidence that oral contraceptive pills could offer protection against some athletic injuries by stabilizing and reducing hormonal fluctuations.

Tracking changes over time is an important way to develop an understanding of your unique patterns. A clear picture of your baseline and changes gives clues into the relationship between your cycle and physical activity. Shifts throughout your reproductive life stages may guide changes to your fitness plan over time. You may find that certain phases in your cycle feel better for certain types of exercise, while others feel better for different activities. Remember, giving yourself permission to rest and recover is always okay.

It is important to discuss menstrual cycle changes and concerns with your healthcare provider.

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