high-intensity interval training (HIIT) was king. Now that gut-it-out-and-get-the-glory work might need to share the crown with slow and steady efforts, thanks to what they do for your body, your longevity, and maybe even your mind. These are the famous zone 2 workouts—keeping your heart rate between about 70 and 80 percent of its maximum—that runners, smart gymgoers, and everyone with a podcast is talking about these days. Think of zone 2 as the range between easy and moderate cardio, where you can carry on a conversation but someone on the other end of a phone would
