MAKING SURE YOU'RE 'HIITING' IT RIGHT!

The rules of HIIT are pretty simple: work really hard, rest, then work really hard again. If you’re taking a group fitness class or working out with a trainer, they’ll time your sets and rest periods and guide you as you go. But you absolutely don’t need a fancy gym, workout plan, or even any equipment at all—just find an activity that gets your heart rate up, and then apply the HIIT format to it.

A good place to start for beginners is with a 1:2 ratio of work to rest. So basically go all out on a chosen activity for, say, 30, 60, or 90 seconds, rest for twice as long, then start on the next set. (As you get better you can transition to a 1:1 ratio.) “Within those confines the possibilities are endless," Sulaver says. "You can sprint. You can use the assault bike. You can run stairs. It’s all technically HIIT, as long as it’s intense,” Sulaver says.

A typical HIIT session is about 20-45 minutes of working and resting. (Another popular workout similar to HIIT is Tabata training, where you are on for 20 seconds, off for 10 seconds, repeated for four minutes.