Between the hit of endorphins, the post-flow savasana bliss, and the knowledge that you did your body and mind a solid, working out should make you feel good.

But from time to time, you may find that while chasing that runner's high or back squat PR, you suddenly find yourself keeled over, wanting (or worse, needing) to puke.

This common phenomenon is known as exercise-induced nausea, and it’s a bit like vaginal soreness after a weekend-long sexcapade: annoying but normal, undesirable but treatable, and one of those things that just happens to some women more than others. Here's what you should know about why it's happening, when you should worry, and what you can do about it.

First things first: It doesn't mean you're out of shape

There’s a misconception that getting queasy during or after exercise is an indication of your overall athleticism. But that’s not true. “From beginner exercisers to Olympians or endurance athletes, exercise-induced nausea can affect anyone," Brian Babka, MD, sports medicine specialist and team doctor for Northern Illinois University Athletics, tells Health.

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"It’s not really related to how conditioned you are,” Dr. Babka says. In fact, a small study published in Appetite in 2001 concluded that training did not decrease exercise-induced nausea.

So if your fitness level isn’t the cause of exercise-induced nausea, what is? Experts say your digestive system is to blame. More specifically, exercise interferes with the the gastrointestinal (GI) tract, which can result in symptoms like nausea, vomiting, and queasiness.

When you boost workout intensity, your gut can suffer

When you’re working out, blood flows to the muscles you're moving and the critical organs that are working—like the heart, lungs, and brain. That means there's less blood being distributed to the digestive organs, which puts a pause on the processes that break down food in your stomach. 

This process is important from a survival standpoint, Michael Richardson MD, a family physician at One Medical Group in Boston, tells Health. "Digesting your food probably comes secondary to running away from a bear," he points out. But in today's world—when we're usually running for fitness or for fun—it mainly becomes an unpleasant side effect.

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According to Dr. Babka, some workouts command more blood flow away from the GI tract than others. And the more blood that's diverted, the more intense your symptoms will likely be.

“Due to the size of the muscles in the lower body—like the hamstrings and quads—and the overall volume of a leg-day workout, leg day may leave you more prone to this sensation,” he says. High-intensity interval training (HIIT) can also exaggerate this response. 

However, it’s important to recognize that high-intensity workouts or leg day aren't necessarily better (or worse) than other forms of exercise, says Dr. Babka, or that nausea is the sign of a really good workout. High-intensity CrossFitters, endurance athletes, and power lifters may be at higher risk of exercised-induced nausea, he says, but "it's simply a symptom of lack of blood flow—or an indication that you didn’t choose a good pre-workout meal."

Yup, what you eat and drink beforehand matters

“The largest factor in whether or not you’ll experience this nausea is what and when you ate ahead of time,” says Dr. Babka. Jim White, RDN, an exercise physiologist and owner of Jim White Fitness and Nutrition Studios in Virginia, agrees.

“Eating too close to your workout won’t give your digestive system enough time to start breaking it down, but eating too early may result in your feeling hungry and sluggish,” White tells Health. “Everybody is different, but eating one to three hours before working out is the suggested window to prevent abdominal discomfort while still fueling your performance.”

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Foods high in saturated fat—bacon, French fries, and burgers, for example—take longer to process in the stomach, so the delay in digestion can create a “deadweight” feeling. “Fatty and greasy foods also stimulate your body to secrete bile to help digest the fat," says Dr. Richardson. "This bile can add to the gastric pressure and worsen nausea."

White adds that other foods can add to GI distress, "including spicy foods, items containing caffeine, and highly acidic foods.”

So what should should you eat? Focus on lean protein and complex carbs, which will fuel your workout, suggests White. He recommends a slice of whole-grain toast with almond butter, a banana with low-fat Greek yogurt, or a cheese and turkey roll-up.

Dehydration is another possible culprit of exercise-induced nausea, says White. "During exercise, the body loses water through sweating in an effort to cool down," he says. "So not drinking enough water ahead of time can increase the symptoms." The solution is straightforward: Drink water at a steady rate throughout the day.

What if you get nauseous mid-workout? 

If you’re in the middle of a workout and nausea hits, Dr. Richardson says it shouldn’t be ignored. “Often, nausea is our body signaling that we are pushing ourselves too hard or that you’re not resting enough between sets,” he says.

To calm the queasiness, dial back on your intensity and try walking around at a slow or moderate pace. “If you stop exercising too quickly, the nausea may get worse because there will be a massive change in where the blood flow is going in a short period of time,” says Dr. Babka.

That’s one reason many running races have participants walk down a shoot after they cross the finish line, he explains. If you’re in a group fitness class, try walking to the water foundation or taking a step back and walking in place.

The bottom line? Exercise-induced nausea isn't fun. But if it only happens once in a while—and it's not accompanied by more serious symptoms like fever, really bad muscle cramping, chest pain, a complete lack of sweating, or brown urine (which is a sign of the a dangerous condition called rhabdomyolysis)—Dr. Babka says it’s probably not something to be too concerned with.

If you constantly find yourself feeling nauseous, on the other hand, talk to your doctor to rule out more serious medical conditions. Or, try scaling back your workouts: You may be over-training, and your body may be telling you to take it easy. 

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