So you are at the gym, in the middle of an intense workout and all of a sudden you get this pulsating headache out of nowhere. The fighter in you says you should ignore it and keep powering through. But the pain is stubborn and doesn’t relent. What’s going on?

Sounds like you’re suffering from an exertion headache—a type of head pain triggered by exercise. Exertion headaches aren’t as well known as migraines or stress headaches. But they can be just as painful, lasting from five minutes to 48 hours and putting a dent in your workout or the rest of your day.

Exertion headaches tend to happen when you’re sweating your hardest; they’re caused by increased pressure on the blood vessels in the brain. They generally occur during strenuous exercise like biking, running, or weightlifting, according to the American Migraine Foundation. Here’s what doctors say you should do if you develop one of these skull throbbers, plus how to keep them from coming back.

Dehydration
“You probably sweat more than usual during a workout, so it’s important to rehydrate with approximately 20 to 32 extra ounces of water for every hour you exercise,” says Rudman. “Especially during the winter months in colder climates. Heat is blasting all day in the home and the workplace, creating a very dry environment, dehydrating you even more.”

Reduce your intake of alcohol or caffeine
If you regularly indulge in alcohol or caffeine, it is possible that either or both are leading to some of your exertion headaches. Try reducing your alcohol intake—doing so will have other health benefits anyway.

Low blood sugar
Skipping a meal or a pre-workout snack can bring on the head pounding, too.

“The brain uses more blood sugar than any other part of the body,” says Carolyn Dean, M.D., a Hawaii-based doctor specializing in nutrition and naturopathic medicine. “Low blood sugar occurs when you are malnourished or even when you skip meals. It also occurs in individuals whose adrenal glands are depleted and can’t mount the necessary adrenaline response to raise blood sugar when it gets too low.”

Upper body tension
Your brain’s anatomical neighbors could be what are plaguing it.

“One of the reasons why exercisers get a headache after working out is because the muscles of the neck and upper back tighten up, pulling on the muscles of the head,” says Robert Herbst, strength coach and world champion powerlifter.

Warm Up
Get your blood vessels opened up before your intense workout with a solid warm-up that gets your heart pumping.

Increased pressure in your head
But what if you know you’re hydrated and well fueled for your workouts? Intense or prolonged cardio or weightlifting workouts could be to blame. Though the exact reason for it is debatable, the Mayo Clinic suggests exertion headaches may develop when strenuous exercise expands blood vessels in the brain over a prolonged period, leading to the pounding pain you feel afterward — which could last for as little as five minutes on up to 48 hours, according to AMF.

What to Do When You Feel a Workout Headache Coming On
Sometimes exertion headaches happen no matter how many precautions you take. In those instances, you can opt to take an over-the-counter pain reliever, like ibuprofen (Advil, Motrin) or naproxen (Aleve, Naprosyn) 30 minutes before your exercise sessions, to reduce inflammation and (hopefully) the tension.

Another option is to down a drink with plenty of electrolytes, like coconut water, as soon as the symptoms start. And if the pain is really bad, cut your workout short and rest until it subsides.

Headaches during or after exercise can put a real damper on your routine, but recognizing the triggers — and preventing them — can get you back on the workout wagon, headache free.