You’re halfway through a high-intensity run or a round of weight training when you suddenly feel nauseous and dizzy. You’re forced to stop, sit down, and rest to catch your breath. Exercise-induced nausea is a common phenomenon, one that most people, fitness professionals and beginners alike, have experienced. So why does overtraining cause nausea and dizziness? Read on to find out.

During exercise, your heart rate increases and increases with your activity level. Blood flows to your muscles so they can get the oxygen and nutrients they need to function. When running, you should exercise at 50 to 85 percent of your maximum heart rate.