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"How does running on a treadmill compare to running outside?"

My wife and I are having a debate. She says that the treadmill makes it easier since it's moving for you. But I think that depending on your frame of reference they should be more or less equivalent.

If the treadmill says I can run a 5K in 30 minutes, does that mean I would be able to run a real 5K in that time?
Hi Gabriel,

There are a number of differences between a treadmill and running outside. Some of them matter and some don't. But first you would have to know if the treadmill is calibrated correctly so that the speed and distance are actually accurate. If you are at the gym and one treadmill says you are consistently farther/faster than another, there are inconsistencies one way or another and actually both may be wrong.

That said, let's look at what is different. To begin with you are indoors and don't have to cope with things like wind or weather. A side effect of being indoors though is that it also simulates humidity. If you haven't already noticed, it probably "feels" like you sweat more, but in actuality it is simply not evaporating as well as outdoors. In that case the treadmill might be more difficult. This you can fix by parking a big fan in front of you, which basically amounts to more comfort. Although since I also mentioned wind, the fan does not solve that, since you are not moving through a mass of air, but a small amount is going past you... if that makes sense. You may also have an issue with drier air indoors, and especially if there is air conditioning. In that case, you might find outdoors more pleasant/comfortable unless there is a lot of pollution . These things may not be a big deal.

Probably the biggest issue, tread mills have a lot of give, so you are generally going to experience less impact than on the roads, and you will have substantially less impact if you are hanging on to the rails at all, because then you have transferred a lot of weight to the rails through your arms (like an instant weight loss program). This is important, because impact over time leads to fatigue and especially in your quadriceps. Quadricep fatigue can lead to tremendous slowing. So generally, you would develop more quad strength running outdoors and be better prepared for an outdoor run. Or to put it simply, your body is most comfortable doing what it is used to doing. Going from treadmill to outdoors is a change that your body may not immediately adapt to.

Additionally, (kinda like what your wife says) treadmills tend to force a consistent pace and stride length... or you fall on your face or scoot off the back. This is a great thing for efficient running, but you don't have the machine helping you outdoors. And, that old nemesis fatigue might set in again... which often leads to a degradation of form and efficiency, and of course when that happens you slow down. Add to that other ineffciencies like uneven terrain and turns that can chop up strides etc and tax peripheral muscles and it is a little different ballgame.

Finally, if you have a distraction on your treadmill like music or TV, you have generally turned your brain off to the running, which can be quite a good thing. The more you worry or think about your running and/or pain, the less you are likely to perform well. Just compete and things go well. It could be difficult to find that level of distraction outdoors when you might be worried about things like jostling elbows, cars or dogs for example.

Having said all that, there is a correlation. If you start going faster or farther on a treadmill, the same should be true outdoors. And running faster... indoors or out is something that does benefit your overall running. But, measure like against like. Measure the treadmill against the treadmill and outdoors against outdoors. You wouldn't try to measure an uphill run against a downhill run. But ideally, you would have a mix of types of runs, distances and paces for overall conditioning. And if you have a specific target, like a flat, hilly, dirt, asphalt or otherwise 5k, you would want a training program that approximated those conditions in it's preparations. Or like I said earlier, your body is most comfortable doing what it is used to doing.

So my answer? You certainly could have days where everything lined up and you ran as fast or faster on the roads than the treadmill. But generally I think you would find your treadmill times and efforts to be less work than comparable outdoor running.

Phil Orr

Running | Riverside, CA

June 16, 2016
Is this answer helpful? 4
Hello Gabriel,

The answer is that there is no comparison! You and your wife can put that debate to rest by doing a 5k timed running test one day on the treadmill and another day outside, just make sure you rest enough in between each run. Just to point some things out - when you run outside, you have to  contend with the environment namely the weather, hot, cold, windy, etc. also the surface you are running on - grass, cement, dirt, flat, hilly, etc. if you run on a track is convenient but if you run say at a park and you have to go out on a run away from where you parked your car - now you have a choice to either run or walk back as apposed to running on a tread mill at the gym where you just push a button to stop without having to run or walk back to your car. If you are running to stay in shape - the treadmill will help but if you are running to get ready for a 5k race - then you need to run outside!!

Carlos A.

Running | Gardena, CA

October 06, 2016
Is this answer helpful? 1
Any motorized device forces the runner to overcome their own lapses in energy to maintain an exact consistent pace. Without the motorized belt doing that for you, a runner will ebb and flow in their pace out on the roads according to their own physiologys ability to produce energy.

Therefore having to keep up with a treadmill will force you to use more cellular energy at times you would rather fall into a bit of a lapse. Very few endurance athletes run, bike, or swim the exact same pace

Therefore running outside should and will be easier assuming its the exact same %grade, lack of wind speed or other factors that could cause an increase in metabolic intensity for you.

My suggestion as an exercise physiologist, strap on a reliable heart rate monitor and make sure your hydrated and choose the same flat grade (like an outdoor track) with no wind or same humidity as inside and chart your heart rate and RPE(rating of perceived effort) on a 1-10 point scale and see if the speed is the same. I think you will find your heart rate and effort will be less outside.

Eric Niles

Running | Lexington, KY

June 24, 2016
Is this answer helpful? 0