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Why Does Treadmill Running Feel Harder Than Outside?

Is it all in your head, or is running on the 'mill actually harder? Here are five reasons why the treadmill can feel like a chore.

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For some folks, running on the treadmill always feels easier than when they hit the road. And for some, it just feels the same. For others, it often feels harder—and not just mentally. If that’s you, you might be wondering, is the dragging feeling all in your head? Or is running on a treadmill actually different than running on a track or road?

Well, studies show that it’s a bit of a mental and physical game that make running on the treadmill harder. In one study, for example, runners were instructed to run around a track, then run at the same effort on the treadmill. Their times on the treadmill were significantly slower. But the reason why there seems to be such a big difference in performance in the two different atmospheres is still just speculation. We spoke with running coaches who focus on outdoor and treadmill training to try and get a better idea.

5 Reasons Your Treadmill Run Feels Like a Drag

Here are some theories on why it feels like you’re exercising harder on the treadmill than when you run outside. Plus, we cover a few reasons why you should embrace it, even just a little bit.

Your stride length is different.

In a study published in the journal Biology of Sport, the researchers found that in elite runners who were conditioned to running on both the track and treadmill the outcome was not always equal. On one hand their VO2max was similar when running on the track as it was when running on the treadmill, but their running economy was much stronger on the track. The study authors speculate that this is because of biomechanical adjustments that have to be made when running on a treadmill.

Running on a moving belt is not the same as running on pavement, where you naturally shorten and lengthen your stride at different intervals depending on your speed and what the ground is like. If you’re shortening or lengthening your stride on the treadmill without even knowing it, that could be a factor in why you feel like you’re working harder to keep the same pace as outside.

This is the case even more for new runners. “Stride length can be altered slightly if a runner is not used to running on a treadmill,” says Misty Walker, a running coach with the indoor running training franchise Stride. “Newer treadmill runners may find they will shorten their stride and increase leg turnover causing a slight increase in energy cost. This increase in energy used may make a normally comfortable pace seem a little more challenging.”

You’re keeping a constant pace.

Running on the treadmill can feel progressively harder over time, even when sticking with the same pace. That could be because running at the exact same speed for however many minutes is more taxing on the body than the natural speeding up and slowing down we do on the roads based on hills and other variables.

But that’s not necessarily a bad thing. “The treadmill keeps you at the pace even as fatigue sets in,” says Walker.

And depending on your training purpose, that can be an ideal setting. “If you are training for speed, choosing a treadmill for certain workouts can force you to maintain a certain speed may be optimal,” says Victoria O’Neil who is also a Stride running coach.

Don’t forget the monotony.

It’s no secret why many runners call it the dreadmill—running on a belt gets boring after a while, even if you’re watching TV or listening to music. That becomes hard not only mentally but physically as the workout wears on.

A 2016 study published in the International Journal of Environmental Research and Public Health backs up what a lot of runners all ready know, that it’s easier to maintain attention when exercising outdoors over exercising indoors. And while the study looked particularly at indoor cycling versus outdoor cycling, one can imagine how those results could easily be translated to treadmill running and road or trail running.

One way to beat this feeling? Switch things up with pre-set exercises on the machine meant to simulate a changing landscape or specific workout. Or try a treadmill HIIT program or group treadmill class.

But the boring atmosphere, could also be an opportunity to grow as a runner if you choose to lean into the monotony. As Walker notes, running on a treadmill can help you build mental toughness by focusing just on the running and no other outside distractions.

The calibration of the machine could be off.

Some folks will point to calibration of the machines as a reason why their workout might feel harder at the same pace they keep outside. Just because the treadmill says you’re running at an 8-minute mile pace doesn’t necessarily mean the machine is hitting that exact rate. If you’re curious about this, try going to two different gyms in the same week that have different equipment or test out a friend’s treadmill and see just how much they all vary. We also know that the GPS watches we rely on outdoors aren’t always correct either.

You’re actually working different muscles.

Running on a treadmill is not physically the same as running outdoors. “In general, outdoor running can work the smaller stabilizer muscles that treadmill running may not engage,” says Walker. “However treadmill running is much kinder to joints and ligaments due to a softer surface to land on.”

“When you are running outside, you actively have to push yourself forward using the back of your legs, while the belt actually pulls your forward on a treadmill,” says O’Neil. The way the treadmill belt propels you forward means you use less of your hamstring muscles. Your quads do most of your legwork instead, meaning you’re working them a bit harder than if you were outside. Perhaps this change is enough to mess with your natural running gait and make your effort seem harder.

If you spend any time running on the treadmill, you should consider your perceived exertion and your breathing rate instead of focusing just on your minutes per mile. That way you won’t feel like you’re underperforming just because your pace is a bit slower than outside. And if you’re one of the lucky ones who feels the treadmill is easier, then you can pick up the pace inside to match your level of effort outside.

O’Neil reminds that, though the treadmill may feel harder at times, there really is no right or wrong answer for how you choose to train. Some people are happy to push through any kind of weather to run outdoors, while others might prefer the control of the treadmill. “A mixture of both may not only be helpful to mix up for training purposes, but also is refreshing and prevents redundancy,” she says.