Eating a huge meal before a workout can be a recipe for a digestive disaster. And when it comes to what is best to eat before a workout (and when) there’s a largely established set of “rules” to follow if you want to avoid stomach probs and heartburn. For one, nutritionists suggest avoiding rich, spicy, or high fat meals before a workouts because these foods often can trigger reactions in your gut that, shall we say, express while you’re moving. Despite following all of these said rules like eating easy-to-digest carbs, some protein, and giving plenty of time for my food to digest, I’ve been plagued with mid-workout heartburn.

And so, I’ve set out on a mission to figure out what other sneaky culprits could be behind my workout digestive woes. I like to think that I know a thing or two about workout nutrition—I’m a certified holistic nutrition coach and currently studying for my CPT—yet I decided to hand things over to the experts to shed more light on the issue. Keep reading below for insight from Marvin Singh, MD, gastroenterologist and Erin James, a certified sports nutritionist.

3 sneaky culprits that could be behind your workout heartburn

1.Coffee

As much as I hate to hear it, coffee is one common trigger. While I’m not one to chug coffee immediately before a workout, I can’t fathom the idea of working out in the morning without at least a little coffee in my system. “Coffee can cause heartburn, whether you are exercising or not,” says Dr. Singh. “Caffeinated drinks are a risk factor for acid reflux so if you know you get heartburn from coffee then that might be one thing to consider removing from your regimen or consider how much coffee or caffeine you are drinking at a time.”

Coffee’s not the only caffeinated beverage you might sip pre-workout. Plenty of people down tea, energy drinks, and pre-workout supplements before hitting the gym, which all contain different amounts of caffeine. You might want to opt out of these if you, like me, are noticing issues during your workouts. Otherwise, caffeine is known to give you a nice boost during exercise, and plenty of experts say it’s fine to drink it before a workout.

2. Tight clothing

It sounds counterintuitive given that many of us don compressive leggings and tight tops to the gym, but it turns out the tight clothing may backfire during your workout. “Wearing tight clothes can trigger heartburn. Although most workout clothes are form fitting, especially for women, if something is too tight, it can cause a negative reaction with your body and lead to heartburn,” says James. At the end of the day, wear what you feel most comfortable in, but you might want to think twice about donning something that will squeeze your stomach too tight and could create pressure that could trigger heartburn.

3. Carbonated drinks (including ahem, La Croix)

Carbonated water is hydrating, sure, but the extra bubbles may not be doing you a favor when it comes to workout related heartburn. Lots of us like to sip carbonated water throughout the day, but the fizzy water could be triggering that dreaded burn when you least want it—like in the middle of your plank.

How to prevent heartburn during workouts

The first golden rule of avoiding heartburn before a workout is to allow enough time for your food to digest (about two to three hours according to experts.) “The quantity and type of food you eat can help you determine how long is best to wait before working out following a meal. A banana and trail mix may not require as long of a wait as a pasta dish,” says James.

Dr. Singh echoes this saying that a too-full stomach could set you up for a not-so-pleasant workout. “Heartburn could happen if your stomach is too full or the food in your stomach hasn’t digested well enough before exercise,” he says.  However, timing isn’t the only thing to keep in mind when it comes to avoiding heartburn.

Common foods that can cause heartburn include chocolate, onion, garlic, tomatoes, and citrus foods, according to James. “It’s important to remember that we are all different. One person can eat something and feel great while someone else eats it and gets heartburn or stomach aches. Learn your body and how it reacts to foods before a workout,” says James.

Signs heartburn symptoms could be something else

Dr. Singh points out that heartburn symptoms can be just that—heartburn, and not much to worry about. But some symptoms of more serious issues can mimic heartburn, which you’ll want to get checked out. “First, if you are having chest pain or burning during exercise, you should seek immediate attention because you could be having cardiac chest pain,” says Dr. Singh. Heartburn can cause a burning sensation in your chest, but it’s usually triggered after eating or it may happen at night, according to Mayo Clinic. Bottom line, if you don’t typically have the sensation and experience sudden chest pain during a workout, it’s best to get that checked out by a doctor.

“If you are having a recurrent issue like this, the first thing to do is to seek medical attention. You might need an endoscopy or some other sort of evaluation. And it is important to ensure that the symptoms you think you are having are actually heartburn and not related to your heart,” says Dr. Singh.

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