★ This is not intended to replace medical advice or professional treatment. You've probably heard of HIIT. Maybe you've seen it on a fitness app, heard someone mention it at work, or scrolled past a video of people jumping around in their living room. But what actually

★ This is not intended to replace medical advice or professional treatment. You've probably heard the term "fat-burning zone" before — maybe at the gym, or in a fitness app, or from a friend who swears by morning walks. But what does it actually mean? And does staying