Which Is Better on a Treadmill: Incline or Speed Intervals?

Should you increase your speed or your incline to see maximum benefits?

This story was first published on Greatist.com 

Amy Eisinger—If you’re the type who hops on the treadmill, clicks the quick start button, cranks the speed to a steady 6.0 miles per hour, and runs until you’re really (really) tired, there’s a better, more effective way to work out. Interval training—mixing high-intensity bursts with lower-level recovery periods—saves time, burns fat, and ups your metabolism.

And there’s another bonus: Less is more. Experts agree that incorporating speed or incline intervals once a week is great for those at beginner and intermediate levels; and two to three times a week on non-consecutive days is OK for advanced runners.

So, what’s better: incline or speed intervals? It all depends on your goal.

If you’re totally new to running...
“The number one thing a new runner wants to think about is consistency,” says Sean Fortune, a certified running coach and owner of Central Park Coaching. “You don’t need to be running fast, you don’t need to be running hills, you need to create a routine that gets your body used to running.”

Once you’ve established regular mileage—jogging for 30 minutes several times a week on a flat treadmill for at least four weeks—start playing with speed intervals. You don't need a strict structure to your intervals when you begin, Fortune says. Run fast when you feel good and slow down when you’re tired—a method called fartlek training. “Maybe a good song comes on your headphones—push up the pace and see how you feel,” Fortune says.

If you want a bit more structure, start with a 1:1 ratio: 60 seconds of speed followed by 60 seconds of active recovery, suggests Cristine Agresta, Ph.D., a fellow at the Michigan Performance Research Laboratory at the University of Michigan. Active recovery means taking the treadmill down to a comfortable, slow jog or even a walk so you can get your breath under control. And while it’s OK for beginners to start upping the incline during a brisk walk, don't take on too much too soon. “You want to strengthen the foot, the ankle, the lower leg,” Fortune says. “Playing with an incline could potentially lead to shin splintsplantar fasciitis, or knee problems.”

If you’re aiming to build muscle...
Hills build muscle by working many different parts of your lower body, from your gluteals to your hamstrings and even your trunk extensors, Agresta says. To start, find a pace that's a quick walk—typically somewhere around 3.5 or 4.0 miles per hour—and then slowly turn up the incline between 5 and 7 percent, says Erica Tillinghast, a certified personal trainer and the global education manager at Precor. “See if you can maintain that same pace as you creep up the incline,” she says.

One catch: Don’t hold on. “If you feel really unbalanced, then of course hold the handrails,” Tillinghast says. “But in general, if you’re holding on, it’s kind of cheating.” Instead, swing your arms naturally, which helps improve coordination and core stability.

When you're ready to add intervals, pick a relatively steep incline (about 6 or 7 percent) and a moderate incline (2 or 3 percent). Aim for 30 seconds on the steep incline at a challenging pace, then bring it back down for a two-minute recovery at the moderate incline and a slower pace, Fortune says. Repeat those intervals five times.

If that’s too much, try a 1:1 ratio—60 seconds on, 60 seconds off—with a moderate hill and a flat recovery, suggests Jinger Gottschall, Ph.D., an associate professor of kinesiology at Penn State. As you improve, increase your work time and decrease your rest time until you spend 60 seconds on an incline at a quick pace and only 20 seconds recovering.

One more note: If you have any knee pain, either stop or take the incline down. Hills put more stress on the knee, which can lead to patellofemoral pain syndrome (a.k.a. "runner's knee") if your other muscles aren't strong enough.

If you want to lose weight...
For those looking to eliminate excess fat, the incline button could become your new BFF. “If someone is overweight, I would definitely recommend hill work over speed work," Gottschall says. In part, what helps someone lose weight is improving their lean muscle to body fat ratio—and that’s where building muscle from incline intervals comes in handy, Agresta says.

If you're unsure where to start, select a “hill” or “incline” program on your treadmill. You can adjust the program settings to your preferred level of difficulty, so even if you’re a new runner, there will be a good fit, Tillinghast says. “One of the biggest mistakes I see is that people will just hit the quick start button, and think they’re working harder than they are,” she says. “Anytime you can get involved in a program, often it will push you harder than you might on your own."

If you want to PR at your next race...
It probably won't come as a surprise that if you want to run fast you need to, uh, practice running fast. And unless you’re training for a particularly hilly course (like an obstacle course or the Boston Marathon), it’s more beneficial to focus on speed, Fortune says. In fact, a recent study found training on a level-grade route produced greater gains for runners than uphill training.

The frequency and intensity of your speed intervals greatly depends on your individual race, but in general, consider trying a short, very fast interval or a long interval that's slightly faster than your typical pace. For instance, if your usual race pace is 6 miles per hour, ramp up to 7.5 miles per hour for 10 to 20 seconds, then slow to 6 miles per hour for a two-minute recovery before amping up again, Tillinghast suggests. Alternatively, you could speed up to 6.5 miles per hour and hold that for two minutes before a two-minute recovery period.

The Takeaway
Hills and speed work both have merit. Whichever you choose, the key is to take it slow. Add your incline and your speed gradually, using the 1:1 ratio (60 seconds of work followed by 60 seconds of active recovery) as a general guide. And remember: Less is more. Once a week may be all you need to reap the benefits of your new routine.

More Reading:
How To Make The Most Of Treadmill Running
5 Easy Ways to Beat Boredom on the Treadmill
The Interval Running Workout to Make Time Fly on the Treadmill