By John Post, MD
Here’s one for which every running shoe shop employee thinks they know the best answer.
If you just apply a little common sense, and physics of course, you can figure out what’s best for your training be you a 60-mile-per week athlete or one with lesser aspirations.
Ready? They’re equal. Since both concrete and asphalt are easily 1,000 times harder than the sole of your new model running shoe, there’s no significant hardness difference. But having said that, blind fold an experienced runner, have him/her run on each surface, and even blindfolded they can tell you the difference. Read on.
There’s this number called Young’s modulus of elasticity. I’ll reproduce it here in case you’d like to use it for your shopping list, to calculate the gas mileage in your Jeep, or perhaps the proper pH of the pool.
It’s the measure of stiffness of a solid material.
If you were to make a quick pit stop by Google you’d find a real range of answers like:
“The impact to your body’s joints as you run is an important factor to consider. Although concrete and asphalt are each hard surfaces, concrete is harder and might result in more joint pain.”
“With all other factors being the same…the difference between the two surfaces is like the difference between a runner weighing 160lbs or weighing 165lbs.” And I thought “heck…as a complete package…I probably gain 5lbs from summer to winter just in extra clothing.” Me, I don’t avoid concrete surfaces.”
Or the one that makes the most sense scientifically:
Slowtwitch Johanthan Toker, Phd. “The difference between concrete and asphalt is a bit like the difference between a standard HDTV and higher resolution TV, where the limiting factor becomes the eye’s ability to observe the difference. The difference can be measured, but the difference is not significant in the greater context of the situation. In the case of running, both concrete and asphalt are very hard and deflect very little. The fact that one deflects a tiny bit more than the other scientifically does not translate to an observable difference in impact, especially when running is considered to include the impact absorbed by a running shoe and the sole of the foot.”
So if we look at the quote that may best sum this up, from Paul Osepa on Cool Running:
“In running shoes, training on concrete is like adding one extra stride’s worth of shock for every every thousand strides that you would take on asphalt, or about one stride per mile.
“Since the cushioning difference between any two shoe models is much more that 0.01%, I submit that shoe choice, and not surface choice, is the only thing that matters for injury prevention on hard surfaces.”
It’s worth noting that concrete is generally the most consistent surface material, while asphalt is typically cambered.
But, can an experienced, blindfolded runner tell the difference between running on concrete versus asphalt?
Absolutely. Maybe it’s the friction difference between a porous surface and one that’s less so. Maybe it has to do with the fact that many asphalt roads are cambered, angled toward the curb for drainage. Possibly the way a foot strikes a slightly porous substance is different. I don’t know. But there’s a difference in feel. That said, a runner doesn’t need to choose one over the other to have a successful workout without fear of increasing the potential for injury. But if you have the option of grass, dirt or the track, I’d take it.
Read more from Dr. John Post at www.johnpostmd.com.