As she entered her twenties the migraines became more frequent (five times a month) and intense, to the point where all she could do was lay down in complete darkness. She tried to identify and avoid her triggers, but nothing seemed to help. She also started working out, eventually finding a high-intensity group fitness class she took once a week. “Within about three classes, I started to notice that, like clockwork, later that afternoon, I’d have a migraine,” says Froese, who was 26 at the time.

She loved the endorphin rush, so the Clearwater, Florida resident managed the resulting pain with a combination of ice on her head, over-the-counter migraine medication, and sleeping. After three years, though, the post-workout migraines were too much. “I have never liked any workout as much as that class, but I just couldn’t continue,” she says. Froese switched to indoor cycling, which, to her surprise, actually helped her migraines.

“The brains of people who have migraines want things to be the same all the time.”

Like Froese, many of the 39 million Americans who experience migraines report that working out can induce intense head pain, oftentimes causing them to give up sports and activities they love. Migraines are the sixth-most disabling illness in the world, causing throbbing, pulsing head pain, often accompanied by nausea and sensitivity to light, sound, and odors. In the past, researchers believed the dilation and constriction of blood vessels in the head caused migraines. However, “the pathophysiology of migraine is very complex and is far more so than we once thought,” says Kevin Weber, MD, a neurologist at the Ohio State University Wexner Medical Center. What experts do know is that several things can trigger a migraine, including stress, hormonal changes in women, alcohol, changes in sleep or weather, certain foods, and, as Froese experienced, physical exertion.

In a 2013 study published in The Journal of Headache and Pain, 38% of migraine sufferers reported exercise-induced migraines, with more than half saying they stopped the offending sport (most often running or racket sports) as a result. A few chemicals in the body may explain this connection, namely increased levels of hypocretin, calcitonin gene-related peptide (CGRP), or lactate, Weber explains.

Hypocretin is a chemical signal in the brain that helps regulate sleep. But many of the functions regulated by hypocretin are impaired in those who have migraines, and some believe hypocretin may cause symptoms such as yawning or fatigue that can occur before a migraine, Weber says. What’s more, intense exercise can impair sleep, and poor sleep can be a migraine trigger. CGRP is another neuropeptide that’s associated with migraines — to the degree that the FDA has approved drugs comprised of anti-CGRP antibodies to prevent the headaches. Lastly, lactate (or lactic acid) is a byproduct of anaerobic exercise the body produces for energy purposes. Increased lactate levels have been found to be associated with increased migraine attacks, Weber says, but whether lactate causes migraines or is a byproduct of migraines is still unclear.

“When things change — such as rapid changes in body temperature, getting the heart rate up by jumping around, bright lights in a gym or outside, or changing position quickly — it can trigger a migraine.”

But there may be other factors too, which all come down to your body trying to maintain homeostasis, says Carolyn Bernstein, MD, a neurologist at the Brigham and Women’s Hospital who specializes in headache medicine. “The brains of people who have migraines want things to be the same all the time,” she explains. “And when things change — such as rapid changes in body temperature, getting the heart rate up by jumping around, bright lights in a gym or outside, or changing position quickly — it can trigger a migraine.”

Additionally, dehydration can lead to migraines. “Most of us don’t drink enough water,” Bernstein says, “so sweating can exacerbate the problem.” And anything that involves pounding up and down is typically out of the question for migraine sufferers. “When I run, I feel like my head is shaking at the same time — it’s like a head earthquake,” says Claire Lee, 24, of Houston, Texas. “I can’t be hard on myself. Running rigorously, jumping, burpees, or lifting heavy weights puts too much stress on my body and does not help at all.”

But here’s the paradox: Working out has also been shown to help prevent or alleviate migraines. In a review of six studies published in The Journal of Headache and Pain in January, European researchers found that aerobic exercise can reduce the frequency of migraines. Other recent reviews suggest that exercise also helps with the severity and duration of migraines, improving the overall quality of life for people with the disease.

“Exercise promotes anti-inflammatory chemicals and decreases pro-inflammatory chemicals in the brain. Exercise also increases beta-endorphins, which modulate pain,” Weber explains. What seems to help best, according to science, is moderate-intensity cardio aerobic exercise such as swimming, indoor cycling in a cool room, walking, or other activity that is typically performed at a continuous rate for a long period of time. Think “steady-state” cardio, not interval training.

“Migraines are kind of like cold sores. You can feel them coming and know in your gut if it’s going to be a bad one.”

“I’ve always worked out, but for my migraines, going outside for a walk or doing some stretching and breathing really helps,” Lee says. “I recently started doing gentle, basic yoga because I couldn’t do other workouts, and that helps lessen the severity too.” But if she transitions too quickly between poses, yoga can worsen a migraine.

The relationship between exercise and migraine varies from person to person, Bernstein says, and it all comes down to the type of exercise, intensity, and personal pain threshold. For example, for most people with migraines, running is too much pounding and can trigger headaches, but there are exceptions. “I have patients who are marathon runners,” Bernstein says. “If you can persevere through the first 20 minutes of the workout and any pain, your body begins to make the beta-endorphins, and you may start to feel better.”

This doesn’t mean that migraine patients should run 26.2 miles. These types of exercisers know how to handle their pain and have conditioned themselves for running long distances. But for most people with migraines, it makes sense to exercise regularly. “The fitter you become, the better your body can handle the stress of a migraine when it does occur,” Bernstein explains. “If you are conditioned, every organ system works more efficiently, and the better your body is able to stand any insult, including migraines.”

There’s no way to know what types of exercise will help or hurt someone who has migraines until they try them for themselves. While it takes some trial and error, building a fitness program can be a natural alternative to medication for managing migraines. Still, it’s not a cure-all.

“Migraines are kind of like cold sores. You can feel them coming and know in your gut if it’s going to be a bad one,” Froese says. “Depending on what stage of the migraine I’m in, exercise makes a great treatment for its ability to improve blood flow, restore my mood, and get me out of my head and into a better mental space. But if we’re talking about the later stages of a migraine, no, you will not see me at the gym. You’ll see me in bed with the lights off and a pillow over my head.”

Now 33 years old and about five times more active than she was in her twenties, Froese’s migraines have also improved to only one to three per month, and she credits her fitness routine for some of that. She sticks to workouts like indoor cycling or moderate weight training rather than running on a treadmill or doing high-intensity interval training or anything that calls for jumping.

Bernstein and Weber encourage those who experience migraines to find an activity they enjoy. Weber suggests his patients gradually build up to about an hour of cardio three times a week since low-impact exercise appears to be best. “I usually recommend it as part of a migraine treatment plan,” Weber says. “Exercise is an easy, inexpensive method that has fewer side effects than most medications.”