Finding the balance of sprints and recovery is key to a successful interval workout.

By Lauren Mazzo
November 22, 2018
Photo: Jacob Lund/Shutterstock

Interval training torches calories and builds muscle. If you're doing your intervals on the track or treadmill, however, powering through is easier said than done. Here, exercise physiologists William Smith and Keith Burns give tips for making the most of your sprints, so you can reap all the epic benefits of HIIT training.

Use the Rule of 15

After the first 15 to 30 seconds of an all-out interval, the body typically enters a semi-hypoxic state, in which the muscles don't get enough oxygen, performance starts to decrease, and lactate (which makes you sore after your workout) builds up, Smith says. To train your body to use oxygen more efficiently, start with 15-second intervals and add 15 seconds each time you exercise until you hit one minute. (Related: This 15-Minute Treadmill Speed Workout Will Have You In and Out of the Gym In a Flash)

Build In Enough Recovery Time

Aim for a 1:4 ratio: If your sprint interval is one minute, your recovery walk or jog should be four. Seem like a lot? "It takes that long for the body to prepare for the next push," says Burns. "Otherwise, the following sprint will be compromised." And avoid going too hard when you're supposed to be recovering. You should be able to say a full sentence, explains Smith. You're not slacking; you're letting your body maximize its work periods. (More on that note, find out why recovery is just as important as an intense workout.)

Keep Moving

Once you've stopped exercising, your body is still busy consuming extra oxygen, rebuilding your muscles, and replenishing its fuel stores-all of which burn calories. (You've probably heard this called "the afterburn effect.") To facilitate the process, walk for a few minutes, stretch your muscles, and stand up and move around every 30 to 60 minutes for the next several hours. "This allows your muscles to recover properly," says Smith.