As a runner (OK, a casual runner) I am cautious about where I put my feet. This is primarily because I don’t want to trip or fall in a pothole, but also because I’m aware that different surfaces have different levels of shock absorbency and thus, will have a greater impact on my joints….or so I thought.
Turns out this may not be true.
It turns out that we humans seem to automatically adjust our running stride to counteract the differences in shock absorbency between surfaces. A professor at the University of Florida, Mark Tillman, validated earlier claims of this human adjustment using force-sensing shoe inserts. He found no difference in the in-shoe forces felt by runners on asphalt, concrete, grass, and synthetic track.
The only problem with making such adjustments is that the change in angle of the knee, hip, etc. may lead to a greater risk of injury on a certain surface. The important distinction is that the injury is not a direct result of a harder surface, but a secondary one. As Alex Hutchinson (PhD), the author of Which comes first, cardio or weights? succinctly summarizes, “…the simple picture – harder surface leads to more pounding leads to injury – isn’t supported by the existing evidence”.
While this information may be useful to a number of you, I would still like you to exert caution when running. Our joints are precious and can take a lot of abuse before breaking down. And yes, they will eventually wear down and call for replacement. So be nice to your joints. Even if the surface isn’t the problem and more the angle of your knee, it’s still a problem.
Hutchinson, Alex. 2011. Which comes first, cardio or weights? McClelland & Stewart Ltd., Toronto.