"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Hear me out: it’s time to get serious about your Zone 2 cardio. ICYDK, Zone 2 cardio refers to a type of ...

Zones are based on your heart rate, but each app has its own idea of where they start and end.

Few would disagree that cardio, also called aerobic exercise, is good for your health. Of the 10 most common chronic diseases, seven are "favorably influenced by regular physical activity," according ...