Which is Better For You: Running Inside or Outside?

In my experience, people feel one of two ways about the treadmill: They like it, or they hate it. As a runner, I have no objection to running on a treadmill—and over the years I’ve built up a case about why people should give them a try!

If you don’t love running in extreme heat, humidity, or rain, a treadmill allows you to run in an air-conditioned environment.
If you have a treadmill at home, you can go for a run whenever you want, at any given moment, for any length of time. It’s easy to squeeze in a quick run (and talk yourself into it) when the treadmill is so accessible.
The treadmill offers a lot of conveniences that aren’t guaranteed when you run outside. There’s a place for your water bottle, you don’t have to hold your phone if you listen to music, and you can run far without physically going far. I can’t tell you how many times I’ve run a certain distance one way and then decided I didn’t want to run that distance back. In such cases, I’ve had to suck it up or commit to a long walk home. On a treadmill, you can just step off.

While the case for trying them is solid, many runners have questions about running indoors versus outdoors. Is one better than the other in terms of training? Is one “harder” than the other? The answers are below.

The difference between running indoors versus outdoors

If you take away the mental component of running for a second and only look at the physical demands, running outside is generally considered more challenging than running indoors. Outdoor running presents more variables and obstacles—the weather, the hills, the uneven terrain, the possible starting and stopping you have to do, etc. Plus, running outdoors means you have to pace yourself (unless you have a running watch or you’re great with time).

On a treadmill, the temperature and climate are controlled, there’s nothing stopping you, and you set the pace and incline yourself. Some runners love this because they can set the speed and not think about it anymore; if they just keep pace with the belt, they will finish their run in the desired time. Running on a treadmill can also help minimize injury—since there’s no rough or unexpected terrain your chances of being injured by that is lowered.

When you factor in the mental aspect of running, though, that’s where treadmill running becomes the harder of the two. Running outside means you’re spending time in nature, which studies have shown has major psychological benefits. You can also run new routes in different places, which can break up the monotony of running. On the flip side, because the treadmill is stationary, the route and surroundings will always be the same. Some runners see this as an advantage and find the predictable, rhythmic quality of the treadmill to be meditative. Others feel it’s boring and dislike the repetition. So while running on a treadmill can be easier on the body, your mind can make it feel just as (or even more) difficult.

The verdict

The best kind of running is the running that you do, whether that’s indoors or outdoors. Both have their advantages and disadvantages, so the one that’s better for you is the one that aligns with your preferences and doesn’t turn running into an activity you dread.

That said, when training for an outdoor road race, you’ll want to clock the majority of your miles outside. Treadmills can be a useful tool throughout your training, but they don’t mimic the terrain and conditions that you’ll encounter on race day. You want to be physically ready for any hills, downhills, and changes of surface that come your way.

In short, run outside when you can, and run inside when the weather’s crummy, you’re low on time, or you need the stability and convenience of a treadmill.