Have you ever felt exhausted during your workout one week and the next you felt like you could run a marathon without breaking a sweat? What accounts for these vastly different experiences?

Was it the number of hours you slept the night before? Or was it that pre-workout snack you ate (which either gave you the extra boost of energy you needed, or sat like a rock in your stomach)? Maybe.

But as it turns out, for women, the fluctuations in our energy levels aren’t random or only tied to sleep patterns and eating habits. There’s a strong chance it has to do with your menstrual cycle and the changes in your hormones. But rather than immediately adding this to the long list of frustrations and inconveniences that often come with the female cycle, it’s worth asking: is it possible to optimize our workouts by learning and embracing the energy fluctuations that come with our cycle?

It probably sounds too good to be true, but fortunately, thanks to the work of researchers and athletic trainers, you can actually maximize your workouts using knowledge of your menstrual cycle in order to be the healthiest version of yourself.

What is cycle syncing?

Aligning your cycle with your workouts and choosing workouts based on the fluctuation of hormones is known as cycle syncing. Cycle syncing uses your cycle to plan your workouts so that your daily movement is optimized to serve and strengthen your body on that specific day. It’s an invitation to honor your body and learn when to push yourself and when to create space for more rest. Ultimately, this knowledge helps you to change the intensity of your workouts because you know when to make it easier or harder based on your cycle.

Exercise science is working more readily with women’s cycles in order to prevent injury and better understand how to maximize workouts. In 2019, the U.S. national women’s soccer team won the World Cup, breaking all kinds of records in the process. The coach credited the players’ stellar performance to her practice of learning the athletes’ cycles and using that information to tailor workouts and have players’ performing at their best. The soccer team not only won the World Cup, it was far better than previous years.

Cycle syncing in the spotlight

Cycle syncing has gained traction in social media thanks to the work of some prolific women.

Gabrielle Lichterman, a woman’s health journalist, began researching the impact of hormones in 1999. She realized that women could utilize their cycle health information to positively impact their daily lives by “anticipating hormonal benefits and challenges.”

Lichterman poured over countless studies regarding the impact of hormones, exercise science, and fertility health. From her extensive research, she published 28 Days: What Your Cycle Reveals About Your Moods, Health, and Potential in 2019, and she offers lectures, consultations, apps for teens and women to track their cycles, and classes in order to help women live in sync with their cycles. Her work laid the foundation for other researchers in the field to continue exploring and working toward understanding women’s physiology, maximizing hormonal fluctuations in alignment with our lifestyles, personal goals, and overall health.

Alisa Vitti, a functional nutritionist and women’s hormone expert, founded FloLiving and published such books as In the FLO: Unlock Your Hormonal Advantage and Revolutionize Your Life and WomenCode. (Of the latter, one OB/GYN who reviewed the book said, “You’ll be able to take your health into your own hands and relish being a woman instead of cursing your gender.”)

Another prolific contributor to the cultural conversation on cycle fitness health is researcher and entrepreneur Dr. Stacy Sims, Ph.D., author of ROAR: How to Match Your Food & Fitness to Your Unique Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life. “Women are not small men,” Dr. Sims explained in a Ted Talk. “We can work with our physiology in order to improve our health outcomes.”

Dr. Sims worked at Stanford for five years where she focused on sex differences in training, nutrition, and environmental conditions. She is a firm believer in having young women talk about their periods at the beginning of puberty and getting comfortable with these conversations in order to maximize their health. Instead of covering up their fertility or feeling ashamed, Dr. Sims encourages women to work with their hormones to better tailor workouts specifically to each body, as opposed to pursuing one-size-fits-all health programs.

How to maximize your workouts based on your cycle

Mairead Suthoff, certified athletic trainer, founder of Lumina Health Services, and certified FEMM instructor, is passionate about helping women understand their fertility and maximize their workouts through her cycle syncing programs.

Suthoff is a firm believer in tailoring workouts to each woman’s cycle: “The knowledge of the cycle and dominant hormones,” she told me, “allows a woman the opportunity to switch up her routine so exercise serves her instead of becoming an item on her to do list.”

In order to understand what it means to cycle sync, we need a brief overview of each phase of the cycle and how to adjust workouts accordingly.

Menstrual-phase tailored workouts

During the menstrual phase, a woman’s hormones are at their lowest point, and this is generally the time when a woman experiences myriad unfortunate symptoms (i.e. moodiness, bloating, cramps, exhaustion). This is not the best time for intense workouts because the low hormonal production doesn’t support it, the loss of blood means lower iron levels and less ability to circulate oxygen. During this time, it also means a woman is more prone to injury due to low progesterone, which helps ligaments and tendons loosen, increasing risk of injury.

Being in the menstrual phase doesn’t mean a woman can’t accomplish a hard workout (she can); but, for many, intense exercise during this phase may not be the most beneficial.

Preovulatory-phase tailored workouts

When beginning the preovulatory phase, hormones are still low, but energy is increasing, and a woman is less at risk of injury. This is the time to start ramping up workouts and increasing intensity.

Ovulatory-phase tailored workouts

Once a woman is in the ovulatory phase, this is when the hormone estrogen is at its peak. Peak estrogen gives us energy and confidence, testosterone provides us with more strength and better depth perception, and, in general, a woman is usually more energized and motivated during this phase of the cycle. Additionally, a woman’s body can recover with less sleep at this time than during any other phase. This is the perfect time to challenge yourself and increase workout length or intensity. With heightened estrogen during this phase, muscles are able to recover much more quickly.

Luteal-phase tailored workouts

The luteal phase lasts from ovulation until your period begins (usually 11-17 days), and has its own phases. In the first week of the luteal phase, progesterone is building up and estrogen is lowering. It is more common for a woman to experience higher energy in the first few days of the luteal phase and then to experience lower energy in the latter part of the luteal phase (about eight days post-ovulation, but this can vary for each woman) when progesterone reaches its height then begins to decrease.

The second half of the luteal phase usually starts introducing PMS symptoms (i.e. bloating, moodiness, tiredness). This is also a phase where an exercising woman is again more prone to injury because progesterone causes looseness of ligaments and tendons. It’s important for a woman to listen to her body and be careful pushing herself with harder workouts.

In addition to this, it’s worth noting the precursor hormone that makes progesterone also makes cortisol (the stress hormone). If the body has any reason to be stressed, it may choose to make cortisol in greater amounts than progesterone as a means of survival, because the body prioritizes its own survival over preparing to support new life. So, if a woman is already someone who is very stressed out, her body can’t differentiate between stressors, so a hard workout may be pushing her body harder than is optimal; and unmanaged stress can lead to a disrupted cycle.

“Sometimes your body responds best and needs rest to recover and be prepared for more,” Suthoff says. “Your muscles heal with food and sleep, for instance. Also, your body adapts to stress. If you aren’t switching things up, both by increasing and decreasing your challenge, then your body will eventually plateau, and you won’t achieve much of anything in the way of fitness goals! So learn to listen and give your body the grace to speak. It will tell you what it needs if you let it.”

How to start cycle syncing

The first step to start cycle syncing is by charting your cycles in order to understand your fertility and hormones. Ideally, it’s best to work with a certified fertility awareness instructor or medical practitioner to learn your cycle and have thorough instruction, so that if there are discrepancies in your cycle, you can work with your practitioner to get the care you need to receive necessary bloodwork, hormonal supplements, and any other additional support necessary. (If you are interested in using fertility awareness charting as a form of natural family planning, having a certified instructor also ensures you can benefit from the high efficacy rates of pregnancy prevention or pregnancy seeking).

Although not every woman’s cycle may require or need hormonal supplements, it’s best to have support as you first start out. There are many nuances to cycle syncing given that every woman’s body is unique. It’s best to work with a professional, so you can tailor your workouts, nutrition, and healthcare to your body. You can start by checking out available methods to pick the best one for you.

If you’re unable to connect with a fertility awareness instructor right now, you can still start charting your cycle with apps such as FEMM that can help you start monitoring your body’s signs of fertility health. The FEMM app will flag if any issues come up in your cycle that look unusual, prompting you to bring your charts to your healthcare provider for more help. There are many other charting apps that fit with different women’s lifestyles.

There is no one right method to help you chart your cycle because your cycle is unique to you, and it’s important to factor in your lifestyle, personality, and charting style in choosing a fertility awareness method.

Let go of shame and embrace your workouts

Fitness and fertility awareness method (FAM) coach Johnna Wilford works with women by encouraging them to chart their cycles and creating workouts that are specific to their fertility. Personally, she likes to add variety to her workouts and may not always choose a workout specific to her cycle, but she knows when she needs to slow down or make some modifications.

“There are certain times when intensity training will be harder and yoga/flexibility will be easier [for me],” Wilford shares on Instagram. “The way I use this knowledge is using it to make sure I’m not beating myself up.”

For Wilford and her clients, this knowledge is empowering and helping women—including herself—to embrace their fertility and the information that comes from charting, and to recognize the bigger picture of their health. With this knowledge, she’s working to remove shame from workouts and acknowledging that exhaustion, tiredness, or bloating is more likely tied to physiological changes, and it’s okay to be gentle as needed.

Cycle syncing is far more than family planning, although that is a factor for many women. Charting your menstrual cycle and embracing your fertility allows you to engage in your health, increase in self-knowledge, and advocate for your own body by tailoring your needs specifically to your own physiology.