When you run around a lot, you probably feel your heart beating steady in your chest. But sometimes it can feel like your heart is racing or fluttering, or that your heart has skipped a beat. This kind of feeling is called a palpitation.
Exercise can cause palpitations, but so can having a lot of caffeine, feeling stressed, or smoking cigarettes. Most of the time, palpitations are harmless, but sometimes they can be part of a bigger health problem. If you ever have them, you should tell your mom or dad.