Running on a Treadmill vs Outdoors

I run on a treadmill most of the time as I find the training environment more consistent that running outside in a changing environment. However, I know many runners consider the treadmill to be boring and has earned the name of ‘dreadmill’. For some people they need to feel the wind rushing past them, they need to see the world outside and they also argue this is what running is about and that it encourages good form.

Aside from these political arguments what are the performance considerations, how do you equate performance between the two? Simply put, it’s difficult and I don’t think you can compare one to another. You could compare running on your treadmill to running outside on a known course but there are a lot of factors to consider.

Ambient Temperature and Humidity

This is one of most significant factors particularly if you’re running at a high rate of work. If your body overheats it will impact your performance greatly, this is why your personal best is set on a cool day. When you’re running at 95% of your maximum capacity you need to stay cool. The temperature and humidity of the environment will dictate how much heat is being dissipated from your body.

Therefore, if I run on a treadmill in my unfinished basement and compare this performance to a treadmill in a hotel gym it will be better at home. You could argue that it’s familiar surroundings and a familiar machine but it’s actually the ambient temperature as my basement is much cooler than a hotel gym. I also run at home without a shirt which I can’t do in a hotel gym.

Treadmill Accuracy

Most residential treadmills and inaccurate, they over-estimate the speed and distance you’ve run. I’ve compared my treadmill using a Garmin Foot Pod and my Garmin 310XT which uses GPS to measure distance. There is very little difference between the foot pod and the GPS measurement, i.e. less than 1% but the treadmill and the foot pod can be different by up to 3%.

Therefore, comparing one treadmill run to another treadmill run is fine but comparing it to outside requires compensation.

Grade

Some people argue that you should run on a treadmill at 2% to factor in the wind resistance, road resistance and uneven running surface in the real world. However, in my experience I find that it’s not required. In my unfinished basement I’m more impacted by the ambient temperature as I can work harder running outside than running indoors due to the cooling effect of the wind. I can run outside at 95% of my capacity but I can’t do that inside for the same amount of time.

Increasing the grade will build up your leg muscles though so it’s not a bad idea as most outdoor running involves some elevation changes. Therefore, I choose to run at 2% for these reasons but not for comparison reasons.

Conclusion

There are a lot of factors that make direct comparison very difficult and all you can do is try to control the factors. I concentrate on the differences between treadmill runs and as long as I’m running further or faster than I ran before I’m happy that my training is working. When it comes to translating this to outdoors, I won’t bother. I’ll simply run outdoors and then compare those differences to each other and look for the improvements again.

I’m slowly training for the Vancouver Sun Run in April 2012 and determined to improve my time from last year as it was disappointing for a number of reasons. With the onset of Winter this means I need to train indoors until around March when I’ll take it outside on to a track. My indoor training is based on fartlek training which is administered through the Adidas Micoach Pacer. My outdoor training is correlated with the Garmin Forerunner 310XT which I’ll be using the race to monitor my pace and heart rate. With the majority of my running taking place indoors the biggest problem I have is matching my pace indoors to outdoors as I simply don’t know what a particular pace feels like. On the treadmill I press a button and I just keep up, outdoors I have to actually propel myself forward — the 310XT helps me to see what pace I’m running and ensures I’m not working too hard or makes me work harder depending on the heart rate monitor.

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