Treadmill or outdoor running?

I've had a few people ask: treadmill or outdoor running - which is better?

Typically, I've been saying that either is fine. But I decided to write this blog post because I actually have a longer explanation than that one. All of which is based on my own experience, so don't consider this expert advice or anything. I hope this helps you think through the pros and cons of the treadmill or outdoor running debate.


I've now completed 5 half marathons and 2 full marathons. Each time, my answer to the question of treadmill or outdoor running has been a little different.

I lived in Alabama for my first half marathon, and I trained between January and March. I ran outside for most of the runs. That's probably because it doesn't usually snow and it doesn't get too cold in the South. (Although this past winter I saw a lot of my friends post about the snow in Alabama. What is happening in the world?!) Sometimes it was could enough for my Southern self to hop on the treadmill (oh how naive I was), but that wasn't for many of my long runs.

I trained for my first full marathon and two of my other half marathons when I was living in Los Angeles. The only consideration for my runs then were weather and traffic. I didn't make a lot of money, and I didn't want to fight traffic just to go to the gym. And the weather question was more about running early enough or late enough that I wouldn't die from a heatstroke. So, again, I ran outside for nearly every run.

Then I moved to Lexington, KY. You Northerners may laugh at me, but this is the coldest place I've ever lived. Like, it actually snows. Not as much as in Ohio, maybe, but Ohio is only an hour away. So we're close enough.

I trained for my next half marathon and marathon in winter. The half marathon was in November, and the full was in January. I couldn't handle the cold, so I ran mostly on the treadmill. That marathon didn't turn out so well for me. I finished, but I had to walk most of the second half of the race. Recovery also took a lot longer than my other races. I struggled to walk for a few days after. I had never experienced that before in a race.

But, I'm older and wiser now. I do think there's a way to incorporate either treadmill or outdoor running into your training. Here are the things I'll be thinking about this time, and that you should, too.


Are you training for a 5k, a 10k, or a half marathon? Obviously, your longest distance of training will depend on your answer. So then you'll want to think about whether you could run the longest distance on the treadmill. Clearly, running 3 miles on a treadmill is different than running 12 (the highest distance my plans tend to go for a half marathon).

When I was training for my first half marathon, the furthest I went on a treadmill was 6-8 miles. I tried not to go any more because it's boring for me. When I started training in 20 degree weather, I didn't care about how boring it was! I ran 14-16 miles on a treadmill...but I remember struggling with more injuries after I did that.

Maybe the reason was age rather than the treadmill (muscle recovery is harder as you get older). But there are some physical differences when you're running on a treadmill versus running outside. Outside, your hamstrings lift your leg behind you to finish the stride cycle. The belt does most of that for you on a treadmill. There is also extra effort demanded of your quads on the treadmill, as you use your quads to push off the belt. Finally, longer strides on the treadmill could cause knee problems. I know this was my problem during those long runs on the treadmill. I pushed myself to run faster for longer, so I know I need to work on that this year.

In general, I'm going to try to stick 6-8 on a treadmill this time. Or at least I'll try to run with a more normal stride if the cold forces me inside. I know a lot of other successful running bloggers do their long runs on the treadmill, so it's really trying things out and figuring out what's best for you and your body.


I had a warning sign before my disaster of a full marathon in January. My half marathon in Bowling Green, KY the November before the full was much harder than I expected it to be. Reflecting on it, I realized it was because I hadn't been preparing myself for race conditions when I was running on the treadmill.

Hills were one difference between training days and race days. It's hard to do hill training on a treadmill, just because you have to input the incline yourself while you're running. I hate having to change my incline while I'm already huffing and puffing. It's good to have some sort of incline when you're on a treadmill, so I usually just put it at 1% and leave it at that.

Another factor the treadmill doesn't prepare you for is wind resistance. Even in ideal outdoor conditions you run against air resistance. You don't have that when you're running inside. (No matter how high the air conditioning is turned up at your gym.) As a result, the paces you run on a treadmill are a bit easier than they would be outside.

Then there are the unlikely ways that the treadmill doesn't prepare your body for the real deal. There's no way of simulating downhill running, and there are no turns. Both of which have different demands on your muscles and joints than you would expect.


If paces are easier on the treadmill, then of course speed is another difference in the treadmill or outdoor running question. The treadmill has been both really good and really bad for my training.

While I trained for the Bourbon Chase, it was summer and fall in Kentucky. So thankfully, no cold weather. But I still did a lot of treadmill work for my shorter runs. I liked using the treadmill for speed, since it pushed me to run faster than I typically would outside. When I run for speed on the treadmill, I always look up an interval workout on Pinterest. Some examples are herehere, and here.

When I was training for my second full, I didn't do speed intervals. I just ran fast for a long period of time on the treadmill. And I got injured - I developed really bad knee pain that wouldn't go away. Like I said above, I think it's because my stride was too long. So that's why I've decided to just work my way up to faster speeds by using intervals. Keep this in mind for yourself - don't go straight to running 8.0 if you're not used to that speed! (Here's a great tool to match your current speed to your number on the treadmill.)

On the flip side, the treadmill could be bad for my speed. I also know there would be days during my training when I went MUCH slower than I needed to because I was feeling lazy. That's not always a bad thing. But if you're doing it more often that you're not - that's not really helping you grow, is it? Just make sure you're aware of the mindset you have when you're approaching the treadmill workout each time.


I think you can get just as much out of running if you're doing it on a treadmill or outside. As you run longer distances, I do suggest you start doing more of your runs outside rather than on the treadmill. But that probably doesn't become a problem until you're training for a half marathon.

Are you using the treadmill to run this week, or heading outdoors? Let me know in the comments, or on Instagram!

This post was first published on Catholic Women Run, a community to encourage women to become healthy, holy, and happy.

Johnna WilfordComment