Follow along with trainers Jacqueline Kasen and Gerren Liles in the workout video above, or if you're ready to HIIT it solo, read the instructions below for a self-guided workout.

In less than 20 minutes, you can sculpt your arms and abs with this upper body dumbbell workout, all while getting your heart ...

Here are some of the “classic” HIIT workouts from the scientific literature: Wingate sprints: 30 seconds all-out, followed by 4ish minutes of rest, repeated several times. (These were ...