This 20-Minute HIIT Running Workout Builds Speed In 4 Weeks

Whether you're head over heels in love with running or more of a recreational strider, there's no refuting its total-body benefits. Not only can adding it to your regular routine help extend your life, but that infamous runner's high is 100 percent a real thing. And one of the coolest things about running is that it's easy to see improvements in your performance (a.k.a. speed) if you commit to a consistent routine. That's where a HIIT running workout comes in.

Integrating high-intensity interval training–commonly referred to as speed work in the running world–can be a total game-changer. "While steady-state running increases your aerobic capacity, interval training also increases your anaerobic capacity," says Hollis Tuttle, an RRCA-certified senior run coach at Mile High Run Club, a treadmill-based studio in New York City. "This additional training will help improve your cardiovascular system, making it more robust and capable of pumping more oxygen-rich blood through your body." Plus, your muscles will also become better at using that oxygenated blood. (You'll also score these benefits from HIIT training.)

In terms of performance, a HIIT treadmill workout will help your stride become more efficient as coordination between your muscles and nervous system improves, which Tuttle says brings about important adaptations to increase your speed. End result: you'll be able to run the same distance in less time–hello new personal record!

Check out Tuttle's HIIT running workout that helps runners amp up their speed below. She says approximately one-third of your weekly training should be dedicated to speed work–assuming you run 6 days a week. If you completed the 20-minute HIIT treadmill workout twice weekly for four consecutive weeks, then you would definitely see an improvement in your 5K time by month's end. (And check out these different types interval running workouts for when you want to switch it up.)

Before you start your HIIT treadmill workout, Tuttle suggests you have a good idea of what your hard run (think 5K), half-marathon, and marathon paces are to help you better gauge your rate of perceived exertion (RPE) throughout the workout. Example: Perhaps you run a 5K at an 8:30 pace, a half-marathon at 9:30, and you clock a full marathon with 10-minute miles.

Oh, and if treadmill running isn't your thing, don't sweat: This routine can easily be done outdoors, too. You're just going to have to do a little bit of recon to find the right hill (and have a running watch with an altimeter that gauges altitude, like the Apple Watch Series 3 or Garmin Forerunner 645 Music). To determine a hill's grade (angle of the slope), you'll divide the rise by run. For example: If the rise is 50 feet over a run of 500 feet, that would be 50/500, or .1-equivalent to an 11 percent incline (which, BTW, is a steep climb). A 12 feet rise over the same 500-foot distance (12/500) will give you a .024 result, or 2.4 percent incline. Once you find a few great benchmarks in your local area, then you'll be set for each and every fresh-air workout going forward. (Gotta say, though, this 30-day treadmill challenge is actually fun.)

20-Minute HIIT Treadmill Workout

"Your goal in the first half of this HIIT running workout is to maintain the same 'easy jog' speed while increasing incline throughout the workout," says Tuttle. "Focus on maintaining a tight core while driving knees up and arms back. The steeper the incline, the bigger the drive. This will translate to speed when you're back on flat ground."

Note: There is a difference between the "easy jog" and "recovery" paces listed in the HIIT treadmill workout. If you want to walk during those recovery periods, go for it. The recovery period is truly whatever you need to feel like you're prepared to take on the next interval to the fullest. The easy jog, on the other hand, should feel like you're still putting in a low-level effort.

Roughly halfway through the HIIT treadmill workout, you'll hit the descending speed ladder. There, the goal is to increase speed (add .1 to 1.0 mph) as the interval time decreases. "As you get faster, tighten your core to reduce torso rotation, and increase knee and arm drive," says Tuttle. And after you cross the invisible finish line of your HIIT treadmill workout and are able to catch your breath, don't forget to give yourself a good stretch.