Here are a few tips if you suffer from heartburn when you exercise.

Time between meal and exercise:
Wait several hours before you do your exercise after you meal in order for to give your stomach a chance to digest your food. Try also not to eat too much at mealtime if you be exercising afterwards.

Don't drink fruit juices when exercising:
As fruit juices aggravate heartburn, avoid fruit juices and fruit flavoured water when exercising. Drink plenty of plain water to keep your body hydrated during your workout.

Take Rennie:
Take an antacid, like Rennie if you do suffer from heartburn when you are exercising.