Indigestion during cardio workouts is common because the muscles used in the exercise divert blood flow away from your digestive tract, upsetting the works. What's even more upsetting is that the impact from running, the forward lean of cycling or improper breathing patterns while swimming can actually promote indigestion by stimulating your insides in uncomfortable ways.
There are some tricks to relieve the pain mid-workout, and a little forethought and planning can prevent it entirely.
Time Your Nutrition
Working out on an empty stomach can leave you depleted of energy, but you must time your pre-workout meals correctly to avoid indigestion. Small snacks of 100 to 300 calories are fine up to the last hour before your workout, but large meals containing lots of fat and protein should be eaten at least three hours prior.
This gives your body a chance to get the digestion started before blood flow is diverted, and you run a much smaller risk of stomach problems during your workout. Experiment to see the timing that works best for you.
Keeping your fluid levels up helps lubricate your digestive system, allowing things to process a little faster. Drinking water during your workout can also help wash the acid back down to where it should be. The American Council on Exercise recommends you drink 16 to 20 ounces of water during the three hours before your workout. Consume 4 to 8 ounces every 20 minutes during your session and, when your workout is done, drink 16 ounces per pound lost during the workout. On extremely hot days, you may need even more water.
If you think you might experience indigestion during your workout, take an over-the-counter acid reducer before you start. Another option is to keep an antacid tablet in your pocket so you can chew it mid-workout if you feel symptoms coming on.
If you know what foods trigger your indigestion, avoid them before your workout or even the night before if you exercise early in the morning. Common triggers include chocolate, coffee, onions and citrus.
Change Your Technique
Leaning forward into an aerodynamic cyclist pose puts pressure on your abdomen and causes acid to rise, so experiment with a more upright posture. The constant impact of running shakes up your insides and causes problems, so modify your gait to minimize bounce and maximize forward motion. As a bonus, this also makes you a more efficient runner.
If you're a swimmer, learn to exhale underwater so you don't have to both exhale and inhale when you turn your head. This way, you'll gulp less air that can cause indigestion. No matter your sport, focus on shock absorption and smooth breathing techniques to keep things running smoothly.