Is soft cardio the missing piece of your workout routine? We spoke to a sports medicine physician and a pro trainer to find ...

We all need a "Zone 2" day -- a low-impact, low-intensity workout -- once in a while. This is especially true for those who find it hard to skip workouts and often push themselves to the extreme.

Many data-driven runners have a grasp on common heart rate metrics, like resting heart rate, maximum heart rate and heart rate zones. But there’s another, often undervalued data point worth keeping ...