The hallmark of HIIT is repeated bouts of extremely hard work interspersed with periods of recovery. During your work intervals, you’ll be pushing yourself nearly to your max, Noam Tamir, CSCS, ...

REHIT is also ideal for people who are experiencing a weight-loss plateau, Mansour says. If you do a lot of high-intensity workouts without much rest, you're likely taxing your body more than you need ...