Add Yahoo as a preferred source to see more of our stories on Google. You're curled up on the couch, finally relaxing after a long day when suddenly, your heart starts racing. You're obviously not ...

Everybody has natural rhythm. Call it your inner drummer--the heartbeat keeps time for the rest of the body. But what happens if your beat's too fast or slow? In medical terms, that's called cardiac ...

Plus, whether a specific HR range is really best for burning fat.