How to work out during each stage of your cycle (and why it matters)

Your workout schedule likely revolves around meetings, deadlines, and whatever you can squeeze into a safer-at-home schedule. But you’re forgetting about another important calendar event when firing up the Peloton bike or searching YouTube for videos: your hormones.

“It’s really controversial, because people are tied to their routines and want to do CrossFit every day,” says Alisa Vitti, the founder of FloLiving, an online health resource that helps women feel seriously better by tuning in the hormonal happenings in their bodies. “You actually need to create a workout regimen that’s sensitive to the neurohormonal shifts that are happening weekly.”

The reason, as she outlines in her new book, In The Flo, is a biological phenomenon called the infradian rhythm: a natural cycle that happens only in females. It’s not exactly the same as your menstrual cycle, but it involves the biochemical changes that come along with it.

Notably, Vitti says, men don’t have the same hormonal changes, so they don’t need to modulate their fitness routines in the same way. Yet most fitness research has been done on men, not women—and female biology is different, with different results. “Women have been operating under the assumption that what is good for men should apply to them, and that they should work out the same way each and every day,” Vitti says. “We have been so hypnotized and programmed into thinking that we have an inferior metabolism, and that we have work out harder to achieve the gains that men make seemingly so much more easily.”

“We have been so hypnotized and programmed into thinking that we have an inferior metabolism.” —Alisa Vitti

As a woman’s metabolism, hormonal blend, and caloric needs shift throughout the month, so does her body’s response to different types of exercise. (If you’ve ever wondered why you can crush a HIIT workout one week and struggle to finish the same exercises the next, that’s why.) “Depending on where you are in your infradian rhythm, you may want to do more intense workouts or lower-intensity workouts,” Vitti explains. If you know how to optimize your workouts for your infradian rhythm, she says, then you’ll see better results: stronger muscles, improved energy, and mental well-being.

“When it comes to working out, depending on where you are in your infradian rhythm, you can do more intensity when metabolism is slower—that’s the first half of the cycle,” she says. In the second half of the cycle, caloric needs increase, metabolism speeds up, and cortisol levels become higher. “This is when you have to modulate your workouts to be much lower-intensity for you to optimize what is happening with you metabolically,” she says. If you don’t work with that, she says, you may lose in lean muscle mass and increase stored fat.

Skeptical? Vitti points out that coaches for the U.S. Women’s soccer team—i.e., the reigning World Cup champs—train according to the infradian rhythm. “Male athletes have been training for decades to optimize lean muscle gain and fat utilization based on their hormonal cycle, which follows the circadian pattern,” she says. “Women have been operating under the assumption that what works for men should apply to them, but it has the opposite effect. But once you understand how the infradian rhythm works, you can’t not follow it.”

Here, Vitti’s expert advice on how to work with your infradian rhythm for optimal health.

Phase 1: Follicular (7-10 days)
The workout:Cardio, group fitness, urban rebounding, anything new

You may have low energy right after your period ends, but within a couple of days, your body will start producing more estrogen as it moves towards ovulation. “Estrogen is a hormone that makes us feel energized,” Vitti explains. You won’t be at full energy, but you’ll have a lot, so she suggests hitting cardio-heavy group fitness classes, especially ones you haven’t tried before. “Do something that feels fun and interesting,” Vitti says. Anything novel works. “You have more new neural pathways being created during this phase, and they’re more easily connected, so you’re more likely to stick to a new exercise plan,” too, she says. “By week three of your cycle, you won’t want to go anywhere you haven’t been before.”

Phase 2: Ovulatory (3-4 days)
The workout: High Intensity Interval Training, boot camps, plyometrics

“This is where we have a sharp rise in hormones, including a dramatic increase in estrogen and a nice surge of testosterone,” Vitti says. So, this is your time to really go for it. You want hard-core, high-impact, kick-your-ass fitness sessions that will push you to your limits. “Go for a run or stream a HIIT video where you’re going through burpees, squats, lunges, and jumping jacks.”

Phase 3: Luteal (10-12 days)
The workout: Megaformer Pilates, barre classes, weight training

At first, it’ll feel like ovulation and you’ll be dominating the treadmill at Barry’s Bootcamp. “Your energy may still be high if you’re healthy,” Vitti says. But during the second half, as estrogen and progesterone decline, you may start to lose a little bit of the fire. She suggests focusing on slow strength training, without as much jumping around. Megaformer and barre classes would work well. Ditto heavy lifting with a trainer.

Phase 4: Menstrual (3-5 days)
The workout: Walking, yoga

“As you move toward the premenstrual and menstrual days, it’s all about flexibility,” Vitti says. That’s because estrogen and progesterone drop off sharply, leaving you with less energy. “This is an intense process for the body,” Vitti says, and you’re likely to feel tired working out on period. Respect it. Take a walk (to the subway) or stream a gentle, restorative yoga class. (Not, she notes, an intense hot yoga class.) “This is the time to enjoy being in your body, to stretch your hip flexors and hamstrings, and unlock your spine from being in the seated position. Make that your intention.”