Here’s How Using a Treadmill Compares to Running Outside

With shorter days, colder temps, and the possibility of black ice lurking on the pavement, moving your run indoors might be looking a lot more appealing. But it can also bring up the question: Is running on a treadmill easier than logging the same distance outdoors? Are you shortchanging your workout—or might the two actually be interchangeable?

The short answer: For the vast majority of pavement pounders, there won’t be much of a difference. Your heart rate and oxygen uptake—how much energy you’re expending—are “quite similar” when you run the same speed on a treadmill and outside, Rich Willy, PT, PhD, an associate professor at the University of Montana and director of the Montana Running Lab, tells SELF.

There are, however, a few nuances to it. Slight biomechanical shifts in the way you run on a treadmill make it gentler on some aches and pains and harder on others. Super speedy folks may need to make a few adjustments, and yep, using one might require a bit more mental toughness than loping through a scenic park or by a waterfront vista. We tapped a bunch of experts—all of whom spend some of their own miles on the ’mill—to break down the differences and how to manage them.

First: A treadmill can make running safer and more accessible, so quit ragging on it.

Please, please, stop calling it the “dreadmill” or saying it’s a torture device. “I always hate seeing people demonize it,” Dr. Willy says. “For some people, that’s the only place that they can run for personal safety, or from a traffic standpoint.”

Take Allison Gruber, PhD, an associate professor of kinesiology at Indiana University Bloomington. “I live in an area where people drive terribly on curvy, wooded roads. There are no sidewalks,” she tells SELF. If she wants to run in the morning—before the sun comes up, which is the most convenient time for her—and avoid a collision with a car or coyote, the treadmill is the best choice.

It also can be a godsend for times when the weather is not ideal (or when snowstorms, freezing wind chills, or icy sidewalks make it downright unsafe), as well when you’re stuck in the house but still want to get some movement in. For instance, Kaitlin Goodman, a former pro runner and the founder and head coach of Running Joyfully, uses it on the days when she doesn’t have childcare for her toddler. “It might be a tool that you don’t love, but it is a tool at your disposal,” she says. “And if the option is run during nap time or don’t run, it’s a great option to have.”

Another way a treadmill can make running more accessible? Say you’re training for a race in a different location—maybe the Boston Marathon, with its famous hills—but you live in the pancake-flat Plains. With a treadmill, you’d be able to use incline to practice the ascents and prepare your body for them (without having to, you know, hop a plane to Massachusetts.) In fact, treadmills like the NordicTrack, with its iFit programming, have certain races pre-programmed; if yours doesn’t, the RunBetter App guides you through when to adjust your incline manually for more than 50 different courses.

But you’re not imagining it: Treadmill running can definitely feel harder than when you’re outside.

In a systematic review and meta-analysis of 34 studies published in the journal Sports Medicine, Dr. Willy and his colleagues found no major physiological differences between running on the treadmill and what researchers call overground running at most speeds. (That holds true for motorized treadmills. Those you power on your own—like the Woodway Curve or the TrueForm Trainer—are more demanding, he says.)

But the data do show the rate of perceived exertion—how much effort it feels like you’re putting in to keep up the pace—is higher on the treadmill.

Why? For one thing, you’re lacking optical flow, or the experience of seeing your surroundings change as you speed by, he says. And, you won’t feel the air rushing past you, either. Because both of these provide information to your brain about how fast you’re moving, any pace feels like a bit more of a slog without them.

The fact that there’s no scenery to distract you also plays a role. That’s why many people turn to TV, podcasts, or even reading to make the miles pass more quickly, Brian Cleven, MS, ATC, an ACSM-certified clinical exercise physiologist at Bellin Health in Marinette, Wisconsin, tells SELF. (Dr. Willy, for instance, can read journal articles during some of his easier treadmill runs.)

You might also find having the pace or time constantly in your face makes it all drag even more. After all, when you’re running outside, you can only steal occasional glances at your watch. In that case, Goodman recommends covering up the display with a towel. Go by heart rate or how hard you feel like you’re working rather than by minutes per mile or miles per hour, and use the buttons on the arms or side of the machine to control pace and incline.

Playing with the incline or other settings can help, but you don’t need to in order to get a “good” workout.

You might have heard that you need to bump up the incline to 1% to create similar conditions to outdoor running. But that’s based on old data, Dr. Willy says. The only time you might consider doing that is if you’re super speedy, going faster than that 7-minute mile (about 8.6 miles per hour, if that’s how your screen displays it). At that point, treadmill running does use a little less energy than running on the ground, and the slight incline offsets that shift, he says.

Still, there are other reasons you might want to toggle the tilt or spice up your run with some speed, including counteracting boredom. “If someone is going to be spending some time on the treadmill, I try to make it fun and dynamic, and we will change it up a lot,” Goodman says.

Some examples of what Goodman calls her “treadmill specials”: a Fartlek or “speedplay” run. After a warm-up, you run intervals of 1, 2, 3, 4, and then 5 minutes at a faster pace. In between the faster segments, run half the time at a slower pace to recover (so 1 minute faster, then 30 seconds slower; 2 minutes faster, then one minute slower; and on up the ladder). Another less-thinky option is to put on a playlist and run one song faster, one song slower.

Just doing an easy run? Switching up the incline between 0 and 1 percent every half-mile, or throwing in a few quick one-minute faster surges every once in a while can help break up the monotony without amping up the intensity too much.

If you’re dealing with injury, there are a few differences between the treadmill and other surfaces you should know.

Dr. Willy has had two hip surgeries, and found the treadmill felt easier on that joint when he was returning to running. So, he studied it, and the data backed him up. Because the belt is moving, more of the force your body applies to the ground to carry you forward comes from your foot and ankle rather than higher up the kinetic chain. (Essentially, your leg is being pulled out from underneath you, rather than having your foot planted and needing to catapult your body over it, Gruber says.)

That means if you’re rehabbing some hip or hamstring pain, the tread might feel better. But if you’re dealing problems lower down, like Achilles issues or plantar fasciitis—inflammation of the band of tissue that runs on the bottom of your foot and a common cause of heel pain—there’s a chance the treadmill will aggravate the issue (and even more so if you crank up the incline). That doesn’t mean you can’t use it, but you should probably ease in even more slowly, Dr. Willy says.

When it comes to the risk of re-aggravating an injury, the treadmill has pros and cons. Of course, you have far less risk of tripping on a rock or a slick spot and falling, and level ground may make some achy spots feel better than navigating the uneven terrain outside. And most runners take shorter, faster steps on the treadmill, Dr. Willy says. A higher cadence is known to reduce tissue damage and may cut the risk of overuse injuries like stress fractures.

Meanwhile, if you’ve had patellofemoral pain syndrome (commonly known as runner’s knee) or pain in your iliotibial band or IT band, running uphill reduces the load on those tissues and may feel better than running downhill or even on the flat—and with the treadmill, you can get the uphills without the downs, so Dr. Willy often uses it during rehab for runners coming back from those injuries.

But on the flip side for the risk of overuse injuries, studies show there’s less variability between your steps on a treadmill, and that repetition may pose dangers. “Instead of just tapping the same spot all the time, we want to tap all over so that we’re not wearing down that one spot,” Gruber says. “Increasing the variability in how you step can distribute the load [of running] better.”

That’s another reason to add some surges or changes in incline, which switch up the way you step. If you’re a treadmill regular, you can also rotate between different types of shoes to further mix things up, she says. (In fact, research suggests that might reduce injury risk regardless of where you run). Or, if your gym has multiple different brands or types of ‘mills, you can rotate between those, too.

So don’t be afraid to give treadmills a try—just ease into it for a smoother transition.

Just like anything else in fitness, try not to go from 0 to 60 when you’re making the switch from roads or trails to the treadmill. If you’ve been running outdoors regularly, you don’t have to start all over with a couch-to-treadmill-5K program. But it’s probably best not to make your first treadmill run a long run or grueling speed session, or to switch from 100% outdoor to 100% tread overnight, Goodman says.

One idea: If you’re training for a longer race and have, say, a 10- or 12-mile run on your schedule, you could run half of it outside and finish on the treadmill. “Just don’t do your first 12-mile run on the treadmill,” she says. “Break it in like you would a new pair of shoes.”

The bottom line? Treadmill running isn’t “cheating” or any less of a fitness boost than an outdoor run. As Dr. Willy points out, many elite runners—including Jakob Ingebrigtsen, an Olympic champion in the 1500 meters and 5,000 meters—do a lot of their interval running on the treadmill (in part, to keep close control of the pace). So if the tread is a safer, more appealing, or the only option, don’t sweat it. “Whatever can keep you running, do it,” Gruber says. “Don’t worry about the small little details.”

Related:

• What to Know About Running Shoe Terminology So You Can Find Your Perfect Pair
• 15 Benefits of Running That Will Make You Want to Log Some Miles
• 5 Running Injuries Every New Runner Should Know About

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