Bridge to 10K

Indoor vs. Outdoor KMs

I've just bought a treadmill to use over the winter on the days when it's too snowy/icy/dark to go outside.

Before this I've only run outside and the treadmill feels a little odd.

Is there any 'difference' between indoor and outdoor KMs? Is it 'easier' to run on a treadmill? I plan on using some of the gradient features (I hate hills outdoors so this will be good training), but am wondering if my outdoors performance will drop when I get back outside in the spring?

7 Replies

I don't think there would be any difference in kilometers but MarkyD is the person who'd know for sure. Many people here have done the whole programme, and are still running solely, on a treadmill.

I did most of it on the 'mill and ventured outside after graduation. I wouldn't say it was harder, just different. The biggest challenge making the transition outside is finding your pace. On the 'mill you just hit a button and away you go. Outside you have to run very, very slowly. Introduce outside running gradually. For example, do one run outside and the other two inside, then the next week do two runs outside and one inside and so on.

I think running on a treadmill is harder mentally but that's only good training for those tougher runs in the future!

Definitely use the hill programmes (the elites use hill programmes in their training 🙂) and set the incline to 1% all the time as that gives a better feeling to outside running.

But unless you live somewhere where the winters are severe there's no reason why you shouldn't continue to run outside in the winter. It's a gorgeous time of year for running.


Thanks for the mention Irishprincess !

I don't have a lot of confidence in the distance-measuring capabilities of a treadmill. So after a session when it says that I've run 4 km, I'll take that with a pinch of salt. To be honest, the distance really doesn't matter and what is important is that you test yourself against the treadmill. So if you always run on a treadmill, then you'll be wanting to cover the same distance on each 30 minute run (ideally, gradually increasing distance) at a similar pace each time. Treadmills always seem to over-record distance.

The difficulty comes when you start to venture outdoors. You know that you can run (say) 5km in 30 minutes, because the treadmill has told you so for many weeks. But outdoors, you find that it is much, much harder. Normally, that is because the 5km figure was not accurate and you were only running 4.5 km (say) on the treadmill. It is just a matter of expectation, and trying to calibrate yourself to running outdoors.

Then there is the whole discussion about surfaces. On a treadmill, there is a bit of 'give' on the deck, and it is just unrelenting flat, smooth and you don't need to look at where you're placing your feet. Outside you have a choice of surfaces. In order of my favourites, there are running track, ashfelt, pavement, tarmac, concrete, sandy track, stony track, muddy track, beach, burning coals, broken glass, grass. All these have an effect on difficulty (or perceived difficulty) of running, and are likely to cause you to run slower. Grass: I hate grass. It hides uneven surfaces and holes and bumps and really causes you to pay attention, and is actually great for strengthening your ankles.

And then outside, you have road junctions, and puddles, and dogs, and street lights, and 'I'll just avoid that piece of rubbish' so the run is swervy and you're paying attention to where your feet will land. This all takes practice, and slows you down.

BUT you get to smell the scent of the evening, and see the sweep of the sky with a sunrise, or sunset, or get to run by the light of the moon. And startle deer and race rabbits... the whole world is out there to run through. Unbeatable. And it doesn't matter if you run through it at a 3 minute-per-kilometer pace, or an 8 minute-per-kilometer pace: you just have to be out there.


Just to add to Irishprincess' and MarkyD's excellent responses:

It is often recommended that you set the treadmill to 1% incline to get it closer to the "difficulty level" of running flat outside. So bear that in mind if you want to train hills, and maybe set the incline slightly more aggressively than you would otherwise have done.

For practicing running downhill you could lift up the rear of the treadmill (it goes without saying that if you do this, make very sure that it's done in a safe way so the mill can't come off it accidentally as you're running, for that would not be fun!).

Running on a treadmill tends to change your gait. Subconsciously you may shorten your stride, and therefore also increase your cadence (assuming the same speed). This has to do with being restricted by the metal around you and a "fear" of running into the console in front of you. It's not actually a bad thing, because increased cadence is often correlated with "better" running form.

If you want to check the speed/distance of the treadmill (which is often unreliable as MarkyD also points out), you could make a mark on the running belt (chaulk is good), gently rotate the belt by hand until it has done a complete loop while measuring it. Then video yourself running for e.g. 10 minutes and in reviewing the video count how many times the chaulk mark passes under your feet. Multiply the count by the measured belt loop length, and that gives you the actual distance you've run. Compare that against what the treadmill itself says, and you now know how reliable (or not) it is.

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Gosh, thanks all, for such excellent responses. I will definitely set the machine to a 1% incline from now on.

I live in the mountains and in about a month's time my outside routes will be covered in slush and ice until about March. I see the treadmill purely as a tool to keep on running throughout the winter and not backslide (though on the good days if the snow has melted I will be outside for sure).

Thanks for the note about the distance on a treadmill being not altogether accurate. I'd read about the impact of shortening one's running gait and wondered if these two factors together would have an overly "positive" (in terms of distance) impact. I'm not too concerned about distance from the machine and am focusing more on how long I run for. When running outside I run to different length playlists (10 songs, 11 songs, and so on) depending on how I feel. So for 'playlist 1' I know I average about 45 mins and 'playlist 2' 50 mins, and so on. As the treadmill is sooooooo boring (looking at a wall is not the same as seeing sun peek over a hill), I have decided to run to the end of the programme I am watching on my iPad. Not very scientific, but I figure if I watch multiple episodes of the same programme that will give me a good idea of how my distance/time is increasing or not.

There has been another benefit from the treadmill, though. My husband (who hates the idea of running and especially running outside) has now decided he will do C25K as a way to get fit purely on the treadmill. So this treadmill will (hopefully) develop an additional runner!

Thanks again to you all for your comments and suggestions. Much appreciated!

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If your that worried about distance covered on the treadmill you could always get a footpod that measure your foot distance more accurately (will have to be calibrated first) but you will need to have something to connect it to IE most garmins, smart phone etc


On the treadmill you can just push a button to stop, so you need to be very committed I suppose.

Running outside, you have to come home eventually so you don’t have a choice, you have to keep going, also breakfast may be calling.......

I was reading once about treadmill running where it stated you did not use all the muscles you would use with outside running. Interesting.


That is very interesting about the muscle use - perhaps it's because when you're outside you're having to turn and move your body around obstacles that you don't encounter on the treadmill?


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