How To Simulate Outdoor Runs On A Treadmill

Woman simulating outdoor runs on a treadmill


By Simon Gould

There are many reasons why you might want to run on a treadmill even if you do most of your running outside. Maybe the weather is bad or too hot. You may have various training routines that would only suit a treadmill. These would be speed work, intervals, tempo or incline running. This is essential when you want to run faster or are training for a race.

Treadmill running does not mimic running outside. There is no wind resistance so running is easier even if you’re running at the same speed. The belt on motorized treadmills also pull away from you which is not something that happens outside. There maybe variations in gradient that a treadmill can’t mimic because they change so frequently outdoors.

The recommendation has regularly been that to mimic outside running you should run on a treadmill at a 2% incline. This would give you a similar time as if you were encountering wind resistance and other determining factors. This has long been thought to be the correct answer, even running coaches will advise a 2% incline.

Is that however correct? The best way to measure this is the actual effort involved in running on that incline compared to running on a level road outside. The measurements would need to be done scientifically and multiple times to check if the right answer is indeed 2%. You would need to accurately measure the energy used by the runner.

So what does the scientific research suggest?

There was a study done on exactly this, it was accepted and published in the Journal of Sports Sciences. This is a respected scientific paper and the studies published are accepted as true. The research was to accurately test what gradient of treadmill running would reflect the energy cost in running outdoors.

Being science they couldn’t just have one person doing some running outside and inside. Then asking how it felt and reading of the time. The study used 9 trained male runners who were used to running outside and on treadmills. They had them do a variety of runs and measured the oxygen consumption of expelled air from the runners lungs. This would show how hard they had to work on each run.

They had the runners run at 6 different speeds with a rest of 6 minutes between each of those runs. They repeated this 6 times to make sure of the accuracy in their results. They also did this on 5 different treadmill gradients plus they ran on a level road surface so they had results for outdoor running to compare.

The paper says they found the results to be very similar amongst all the runners and that they had the definitive answer. A treadmill at a gradient of 0% and 1% were similar to the efforts of running on the road. Gradients of 2% and 3% were very different. They concluded that to replicate outdoor running a treadmill should be set at a 1% incline.

There were slight variations when it came to speed. But their conclusion still stands. For the casual runner who wants to maintain health and fitness, they’re probably best to use no incline. But for the hobby runner who cares about their race times, it may be more important for them to replicate outside conditions, especially if something causes them to have to use a treadmill a lot.

Treadmill running at 1% incline

I’ve done some calculations and someone who weighs 160 lbs and runs on a treadmill for 30 minutes at 7 mph, will burn 447 calories at 0% incline, and 465 calories at 1%. This shows it represents a fraction of extra work to run at 1% incline compared to the flat, but that’s what the numbers say. I used this useful treadmill calories calculator.

Running on a permanent incline on a treadmill is not the most natural of experiences for the runners body. You never encounter a 1% incline throughout a whole race or any other run. Your body’s natural gait has to slightly adjust to this gradient. Serious runners will typically avoid a treadmill where possible. I think this is probably a good thing.

The advice for runners is to only do specific running work on treadmills that can’t easily be replicated outside or are just more convenient. This includes speed training like fartleks, tempos and intervals. Many runners do this already and always have a treadmill for specific workouts as needed. I used to be a member of a gym for this very purpose.

Final thoughts

I personally do my treadmill running flat with no gradient. I don’t feel the need to replicate the level of exertion I would have outside by using a 1% incline. I’ve accepted treadmill running is different than outside, it’s easier and that’s ok. However, I don’t run any races anymore. If I did, then perhaps I might want the treadmill to mimic outside running.

You will never be able to truly replicate outdoor running on a treadmill. You don’t have to deal with the different terrain and the treadmill cushions each stride. You don’t have to do any turns and the deck moves beneath you. Outdoor runners look down on treadmill runners, but sometimes a treadmill is just the most convenient way of getting exercise on a given day.

Thinking of buying a treadmill? Here’s my favorite, I always recommend it when asked.

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