Cindy Kuzma

There could be a number of reasons you're feeling a rapid beat. Here's when to worry about it.

How HR training works, and when it's useful.

Plus, a look at the accuracy of heart rate monitors.

Female bodies just might be built for the challenge of greater distance—as are our minds and hearts. Here, we dig into the science of endurance.

Running changes your brain chemistry in a lot of ways. Here's exactly what happens before, during and after a run.