DW News · Feb 6, 2026 · Collected from RSS
Women in gyms hear it all the time: lift heavy in some weeks, go lighter in others, depending on your menstrual cycle — because your hormones affect your strength. But is it backed by science?
There's a body of research going back at least 40 years, with scientists asking whether hormonal shifts in women influence strength, fatigue and recovery. Over time, that research has filtered into gyms and social media, often simplified into rules like "take it easy during your period" or "push hard mid-cycle." The menstrual cycle is a monthly rhythm of hormones. During the month, two key hormones, estrogen and progesterone, rise and fall, shaping how many women feel, move and recover. Fitness professionals often divide the cycle into four stages: Week one: during menstruation, also known as the bleeding phase or "period" Week two: days leading up to ovulation Week three: after ovulation Week four: before the next period begins And depending on where you are in your cycle, trainers may advise you to lift heavy or go lighter. But what does science say about cycle syncing — is it useful, and who is it for? Strength and timing: Why muscle growth ignores the cycle In a paper published in 2024, researchers searched databases for studies, spanning from 1960 to 2023, to learn about the influence of menstrual cycle phases on muscle strength performance. They found 707 studies but focused on just 22, which met specific criteria. These included studies which had selected women a regular menstrual cycle and where the measurement of muscle strength was done in a clearly defined cycle phase. On average, women performed slightly better in week two of the cycle, when estrogen is rising, but the differences were small. Results also varied widely between individuals. Many of the observed effects appeared in controlled laboratory settings and among trained or elite athletes, where even marginal gains matter. Another study published in 2024 found no meaningful difference in muscle protein synthesis — the process that repairs and builds muscle — between different weeks of the cycle. In other words, the body can build muscle at any point in the month. So, why has cycle syncing become so popular? How do muscles actually work?To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Workouts across the month: Adjust the load, not the habit Workouts aren't just about lifting weights. They can mix strength training with cardio and movement work. And that's good — it allows for small adjustments during the menstrual cycle. For example, in week one, estrogen and progesterone are at their lowest in a woman. The phase is commonly linked to reduced exercise tolerance. She can have cramps, migraines, heavy flow, and very low energy, affecting performance in the gym. "Lower estrogen and progesterone levels have been loosely associated with a decrease in performance," said Natalie Crawford, a reproductive endocrinologist and hormonal health professor at the University of Texas. Crawford said it was best to avoid pushing yourself to exhaustion during the first week of your cycle. Instead, focus on low-impact or low-intensity workouts. In week two, estrogen rises, and progesterone remains low. Many women feel more energetic and focused in this phase of their cycle. "Your capacity to lift and engage in intense exercise is much higher," said Ana Mendes, a fitness trainer based in the Netherlands. Estrogen helps the heart and muscles work more efficiently, supporting endurance and strength. "This is often a good time for longer runs, HIIT workouts or lifting heavier weights," added Crawford. Then, in weeks three and four, after ovulation, estrogen levels drop and progesterone rises. "This is more of a maintenance phase. Some women tolerate it well, others lose power," said Mendes, who often recommends lighter loads, slower pacing, or more restorative workouts during these weeks of the cycle. Women who weight train get these health benefitsTo view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Irregular menstrual cycle? Why listening to symptoms beats the calendar Much of the research DW looked at for this article took a regular menstrual cycle as the standard. But about 14-25% of women have an irregular period. That makes cycle syncing difficult. "Take [cycle syncing] with a pinch of salt," said Emilia Villegas, a hormone and wellness coach based in the Netherlands. Villegas works with women who have irregular cycles and women who are moving through perimenopause, when cycles may change suddenly. Instead of tracking dates, Villegas encourages women to observe symptoms, such as their energy levels, sleep quality, mood, anxiety and night sweats. Patterns often emerge. For women with absent or unpredictable cycles, symptom tracking can be more useful than cycle syncing. It can also flag excessive training stress. "If periods become irregular, it's a cue to reassess recovery, nutrition and workload," said Villegas.The bottom line on cycle syncing, according to science Science shows that the ability to build muscle and strength is not tied to a specific week of the menstrual cycle. Progress is gradual, and consistency matters more than timing. Cycle syncing is not about hormonal "hacks" or maximizing muscle gains. But it can help women adjust their own expectations of themselves, manage fatigue and train more sustainably. "It's about listening to your body and adjusting what you do," said Crawford. "Any exercise is better than none. And it's OK if cycle syncing isn't for you." Mendes applies the same approach. On low-energy days, she doesn't cancel workouts; she adjusts the variables. "If I reduce the load, I increase the number of repetitions," she said. Understanding recurring shifts in energy can help women train smarter, avoid burnout and stay engaged. Edited by: Zulfikar Abbany