Here’s what this health metric really indicates, according to cardiologists. Fact checked by Isaac Winter Reviewed by Vivek Cherian, MD Heart rate variability (HRV) is the difference in the timing ...

Did you know there’s a number that might let you know how stressed you are, whether you have a cold coming on and how to get into the zone if you’re about to present at a big meeting? You can find ...

That tension becomes especially clear with heart rate zone training, a popular five-tier system that endurance athletes use to measure effort and fine-tune performance. The well-known formula is ...