Cycle Syncing Is Trendy. Does It Actually Help Your Running?

There’s a new fad for runners who menstruate: synching your workouts with your menstrual cycle. The idea is that your changing body hormones make certain types of workouts better suited to different times of the month. However, there is not much evidence that suggests this is useful for the majority of athletes, and many experts are not sure about the effectiveness of this approach. Instead, they say it makes more sense to train through hormonal fluctuations.

“We’ve had an explosion of menstrual-cycle-based research looking at how athletes might be impacted, but on a population level, we’ve seen that the menstrual cycle typically doesn’t have a significant impact on most performance metrics,” says Dr. Megan Roche with the Stanford Female Athlete Science and Translational Research Program. “We see that in practice too, where we’ve had athletes performing at extremely high levels throughout every phase of the menstrual cycle.”

So while “cycle synching” may be on trend–the term has millions of views on TikTok and is often a top trending search term–running coaches and experts say it likely just won’t work to adapt your training to your cycle. They advocate instead that runners be aware of their cycles and the impacts it has on their bodies and be ready to adjust if necessary, but not change their training in advance.

Phases of menstrual cycle

First of all, no one is exactly alike and many people who menstruate do not have the perfect 28 day cycle. It can be hard without doing a blood test every day to know exactly what phase you’re in. But through tracking your body temperature and your menstrual period, you can overtime get a sense of what your individual patterns are.

Experts say it’s important to know and understand the phases of the menstrual cycle. There are four phases of them, each lasting about a week, though it varies from person to person. 

Days one to five are when you have your period. They’re low hormone days, with low estrogen and low progesterone, and women often feel lower energy during this time, says Brooke Kalanik, who researches exercise and women’s hormones.

“That can certainly be worse if they are low iron or low in other nutrients, under a lot of inflammation, or during perimenopause when hormone swings from higher to lower feel much more significant,” she says.

Week two is the pre-ovulation phase, where estrogen is climbing up, peaking at ovulation. This is often when women feel their best in terms of mental creativity and clarity and physical energy and stamina, she says.

Next is the post ovulation luteal phase where bodies dip in estrogen and progesterone starts to rise. In this phase, estrogen is lower and progesterone is building, so stamina and energy may decrease, making longer cardio sessions more taxing, while shorter bursts of exercise work better, Kalanik says.

During the final phase, both estrogen and progesterone are on the decline, leading to less energy and more symptoms of PMS, which can make training feel a bit tougher, she says.

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How your training changes during your cycle

Some runners will truly never notice a difference in their running ability no matter what phase of their cycle they’re in. But Holley Samuel, a registered dietician and dedicated runner, says over time she learned to be more attuned to her cycle and the impacts it had on her training. 

She then adjusts not her training plans, but her nutrition and possibly her expectations.

“I do get more tired and sore during the late phase of my cycle, so I may adjust paces, expectations, and weights using the rate of perceived exertion,” she says. “Or supplement with more carbs and hydration if I’m racing during that time.”

Each of these phases can have impacts on your training and running, so women may want to adapt their training to fit what phase of their cycle they’re in. But others don’t see much difference at all.

Some experts say that the first phase of the cycle is an optimal time for women to do their hardest training “because they are hormonally most like men, lower estrogen and progesterone,” Kalanik says. 

However, she says in her clinical experience, women don’t tend to have their best stamina during this week.

Kalanik says the second week may be the ideal training week, because women are burning more fat, have more stamina, build more lean muscle mass, and often hit PRs. 

Then in the third and fourth weeks, training becomes more taxing as stamina decreases, she says. 

However, Kalanik cautions, there are many factors that can impact how women feel, from age to diet to stress level. Her broad recommendations are meant to teach women to be more aware of their cycles, and not to guide specific training.

Should you design training around your cycle?

If you want to experiment with training around your menstrual cycle, the ideal would be to put the most intense exercise on days seven to 14, Kalanik says.

“But while this is how their physiology works, women can often still train throughout their cycle without a lot of modification,” she says. “Some women will not feel these changes in hormones as much as others will and I do recommend we still train throughout the cycle, just tune into these hormone fluctuations to maximize it.”

But Samuel, the runner and registered dietician, advises against these programs. She says women can train at high intensities throughout their cycles. In fact, she recommends keeping training consistent throughout the month, especially if you are trying to train for a race.

She recommends adjusting workouts based on the rate of perceived exertion that day. 

“For example, if you have mile repeats during the follicular phase and run a certain pace, and then repeat that workout or a similar one in the luteal phase and are having a hard time hitting the same paces despite feeling it is very challenging, simply go off effort and don’t worry if the pace slows, you’ll still get a lot out of that workout,” Samuel says. “Same advice applies for weights, you may feel great lifting a certain weight during the follicular phase and then need to back off a few pounds during the luteal phase if you aren’t feeling as great. But this doesn’t mean we simply avoid training and walk and do yoga only when trying to train for a marathon.”

She says avoiding hard training for two weeks every month simply wouldn’t get you to a big goal.

As a coach, Roche says she might adjust training for athletes who are heavily impacted by their menstrual cycle, but only does that individually and “with a lot of consideration for other variables rather than adopting a broad-based menstrual cycle approach for all my female athletes.”

Roche also views the apps and programs promising to optimize training based on menstrual cycles with skepticism–she says they just don’t bear out across the population of menstruating runners and are not based in effective science.

“There are so many variables that feed into an athlete’s response to training,” she says. “While the menstrual cycle is a variable that might impact some athletes, fundamentally adjusting training theory for the menstrual cycle alone might not be the best way to optimize performance for some athletes.”

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What if your race falls during a low energy phase

There are ways to maximize performance despite what phase you’re in–for example cooling your body with ice if your race falls in a luteal phase.

But Samuel says that for recreational level athletes, it’s far more important to be practicing proper fueling than worrying about where you’re going to be at in your cycle for a specific race. 

“All women need to be eating enough total calories, eating enough carbohydrates, protein, fat, getting enough micronutrients, fueling their workouts appropriately, hydrating appropriately, and timing it correctly consistently before we worry about implementing cycle specific nutrition,” she says. “Most women I work with are not covering the bases adequately enough and will therefore not benefit from cycle syncing their nutrition.”

She says if women are covering the bases of getting the proper nutrition, that will make cycles less symptomatic.

Tracking helps, too

To best work within your cycles, Samuel recommends tracking it either in a journal or an app and learn how your body feels throughout different parts of the month. 

“If they can recognize when they tend to feel more worn down, symptomatic, or tired instead of sharp and energetic, they may be able to identify how they will feel on race day if their cycles are regular,” she says. 

Another reason to track is to figure out if your cycles are not regular or predictable. If that’s the case, Samuel recommends working with a dietician and OBGYN to identify potential root causes.

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Roche also says tracking your menstrual cycle is a great way to cue into your body. 

“Menstrual cycles can also be a way to monitor for RED-S, given that low energy availability can cause irregular menstrual cycles,” she says. “I encourage the female athletes I coach to understand their cycles and we work together to talk about their symptoms and how they feel.”

But, she does not ever see a reason to adjust training for all women based on what phase they’re in.

“If I adjust training, it’s done on an individual level, rather than a broad population-level approach for the female athletes I work with,” she says. “The most common situation I see is athletes struggling with intensity in the luteal phase of their menstrual cycle. In this case, we might do more of an aerobic focus to keep the body feeling good, with some workouts here or there so they are also confident and prepared to race in this phase.”