(NEW YORK) — If you’re a female who loves fitness you may have heard the term “cycle syncing,” the idea that you should change up your workouts based on where you are in your menstrual cycle.

The impact of the menstrual cycle in women’s sports has been prominent among professional athletes over the last few years with the U.S. Women’s National Soccer Team tracking their periods ahead of their 2018 World Cup win as a strategy to maximize performance. This year, Orlando Pride, a National Women’s Soccer League team based in Florida, changed their uniforms from white shorts to black shorts to help players feel more “comfortable and confident” while playing on their periods.

Now, curiosity over how the menstrual cycle impacts performance has gone mainstream. The hashtag #cyclesyncing has been used more than 280 million times on TikTok with millions of women sharing how changing their workouts each month based on where they are in their menstrual cycle has benefited their personal health.

Cycle syncing focuses on four main phases of the menstrual cycle: the menstrual phase, follicular phase, ovulatory phase and luteal phase. This training regimen recommends doing different types of workouts for the four different stages of your cycle.

The breakdown of the average cycle syncing training regimen, according to Nike trainer Lauren Schramm, looks like this:

• Menstrual phase: Lasts three to seven days. Rest on days one and two of your period, then use optimal movement for when energy levels are low and rest needed is high with activities such as yoga, walking, and barre.
• Follicular phase: Lasts around seven days. Focus on speed, power and optimal movement for when energy levels are low to moderate and rest needed is moderate with activities such as heavy lifting, HIIT, boxing, dance and track workouts.
• Ovulatory phase: Lasts around three to seven days. Focus on aerobic, endurance and optimal movement for when energy levels are the highest and rest needed is low with activities such as a group fitness classes, long runs, cycling and hot yoga.
• Luteal phase: Lasts around seven days. Focus on mobility, recovery and optimal moment for when energy levels are low to moderate and rest needed is moderate to high. Activities can include mobility training, stretching, breath work, yoga and massage.

Does cycle syncing your workouts really help your performance? How can you effectively track your cycle? Is it one size fits all? We asked the experts.

What experts know about cycle syncing

Dr. Ellen Casey, a sports medicine physician from the Department of Physiatry and the Women’s Sports Medicine Center at the Hospital for Special Surgery in New York City, spoke with ABC News’ Good Morning America about her thoughts on the science of cycle syncing.

While your menstrual cycle will impact your physical performance and energy levels, Casey, who has been researching this topic since 2009, says there are benefits for female athletes to track their cycles, but adds there is not enough scientific evidence to show this structured “cycle syncing” method works for everyone.

“I do think it’s very important for female athletes to track their cycles,” Casey says. “It’s when you try to give a sort of group recommendation that I think [is] where we’re falling short to date in the literature, and where I worry that there may be some overselling of cycle tracking and conforming that to your workouts, because we don’t have the data to support that as a group effect at this time.”

Casey said that everyone’s cycle is different — things like the length of phases and estrogen levels vary for every person. This makes it difficult to track the change in phases without using an ovulation stick every morning, which she said can be expensive and time consuming.

“Even if we know exactly that everybody’s on day 10 of their follicular phase, it’s still going to be different, because my level of estrogen might be totally different than yours,” Casey said.

While the cycle syncing method can be used as a baseline, Casey said without proper equipment, like using an ovulation stick each day, there is no sure, scientific way to tell what phase of your cycle your body is in.

“What would be nice is for everybody to be like, ‘Cool, this is where I’m really going to push my strength gains, and this is where I’m going to do endurance work.’ I think at some point you know, when we can check these markers in saliva or whatever … [but] we’re not there yet with the science,” she said.

How tracking your period can influence your workouts

While Casey said the science is not there for a one size fits all cycle syncing program just yet, she does recommend tracking your cycle to figure out how to get best results for yourself.

“I do think there’s value in individual following,” she said.

Referring to cycle syncing, she added, “I think it’s such a fascinating area and I love that people are thinking of it. So, embrace that interest.”

Schramm said she began tracking her cycles when she noticed she wasn’t able to train in the same way and get the same consistent results that her male coworkers and clients were getting.

“I believe cycle-syncing is something that can be taken as far as you desire, and if it’s of interest to begin experimenting with yourself, after clearance from your doctor is obtained, then I think it’s an ideal approach to movement as someone with monthly hormonal fluctuations,” Schramm said.

Schramm said she has seen improvements in her own training by tracking her cycle and following the cycle syncing method of training.

“Understanding the hormonal fluctuations … has clarified why some days I feel my strongest, have unlimited energy and could workout for hours and then the following week, it’s a struggle to get through my warmup,” Schramm said.

Where to start

If you’d like to start monitoring your cycle in relation to your workouts, here several ways you can get started:

• Consult with a doctor or trainer: If you are looking to begin a cycle syncing-type process, start by making observations regarding your own menstrual cycle, then consult with a trainer or doctor about the best ways to be active while still respecting your body’s needs for rest and energy.
• Track your cycle with apps: Start tracking your cycles. The FitrWoman app, designed by Dr. Georgie Bruinvels, breaks down the four phases of the menstrual cycle and uses evidence-based research to match symptoms and solutions to each phase. This app was used by the U.S. Women’s National Team when training for the World Cup. Other period tracking apps such as MyFlo, Cycles and Period Tracker Lite will help you track your cycle and follow how you feel turning workouts at different points of your cycle.
• Use cycle-friendly training tools: More and more fitness brands are adding cycle syncing training as an option in their training programs. Nike has started a “NikeSync” training program with physiologist Stacy Sims, Ph.D., which includes training plans and nutrition suggestions for every phase of the menstrual cycle. Fitness membership program Les Mills + contains a cyclical training guide that includes four workouts to match each week of cycle. Adidas also offer a free “PE(riod)” lesson plan online developed by Buinvels that helps you better understand working out during your menstrual cycle and gives recommendations for each of the four phases.

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