Wednesday, May 18, 2011

Should ALL runners stop heel striking? Delving beyond footstrike....

In my last post, we discussed some of the underlying causes of running injuries -- poor biomechanics being one of them.  Today I'd like to delve a bit deeper into running biomechanics.

First, several different running footstrikes exist: heel striking, mid-foot striking, and forefoot striking.  If you went to your local 5k and observed the footstrikes of all the runners, you would quickly notice that almost everyone is heel striking.  Most recreational runners in the USA are heel strikers, which is likely a result of wearing cushioned shoes all their lives (with significant amounts of cushioning in the heels of the shoes).  Besides having poorly developed muscles within the foot, these runners might also overstride when they are running.  In many third-world countries where shoes are not as plentiful, individuals tend to be mid-foot or forefoot strikers while running.  Adoption of a mid-foot or forefoot strike is absolutely necessary because a barefoot calcaneus (heel) cannot repeatedly bear the load of our body at the point of initial contact; a healthy arch, on the other hand, is more than capable of bearing this load, which is what occurs during barefoot running.  Therefore, the availability and our choice of footwear certainly impact how we run.

Now, let's take a look at the differences between a heel strike and a mid-foot strike.  I've taken high-speed video using Dartfish software to provide you with a visual representation of each footstrike.  You'll notice in the top video (shod) that the runner contacts the ground first with the heel....and then rolls through onto his toes, at which point he pushes-off.  Conversely, in the bottom video (barefoot), the runner contacts the ground on the outside of his mid-foot....before flattening the foot and then rolling towards his toes to push-off.  Also, take note of where the runner's foot is landing in relation to his center of gravity (location of his pelvis) in each video.  A mid-foot strike forces the runner to strike more under his center of gravity than does a heel strike.  Why is center of gravity important in running?  Just like when we lift a heavy object from the floor, the point at which we initially contact the ground while running should be only slightly in front of our center of gravity (otherwise we are overstriding).  If it is not, we subject our lower extremities to significantly greater impact forces.  However, you can heel strike while still landing optimally under your center of gravity.  In this case, heel striking does not appear to be as bad as many make it out to be.  Unfortunately, very few runners are truly capable of heel striking without overstriding, which may be a result of our footwear.  On the other hand, it is nearly impossible to mid-foot or forefoot strike and overstride...hence the reason why many encourage a switch from heel striking to mid-foot or forefoot striking.  [Note: the current literature has determined that heel striking generates greater impact forces than mid-foot or forefoot striking even if you are wearing a well-cushioned shoe.]

Whew.  That is a lot for anyone to absorb all at once.  Contemplating these points though, many runners ask me whether they should switch from heel striking to mid-foot or forefoot striking.  My answer -- it depends.  It depends upon whether you are currently injured or running pain-free.  It depends upon your running goals.  It depends upon whether you are actually overstriding.  There are too many factors to consider to make a blanket statement for everyone.  What I will say is that many runners could benefit from including barefoot strides and drills on a smooth, grass field (excluding diabetics!).  This barefoot running will reinforce your "natural" biomechanics and help develop the many muscles in the ankle and foot.  You should use it as a SUPPLEMENT to your regular training regimen....just like you might supplement your training with strength training or core work.  Remember, build up slowly.  Start with one 50-100 meter barefoot stride and increase by one each week until you are running 8-10 barefoot strides total following a run.

Let me know your thoughts on the footstrike debate.  I'd be interested in hearing your experiences or stories regarding barefoot running.