I have a lot to say about my first love… running. For me there is nothing more freeing than feeling the ground under my feet. Just me and the elements on a long, hard run. And as distance running is rapidly gaining popularity, it is easy to see why many people would agree with me. Yet despite our growing interest in the sport, incidence of running injuries are consistently reported between 60-80% and these numbers may be rising. So what is it about running that is causing so much grief for those who enjoy it?
One contributing factor to running injuries that is continually being is vertical loading rates. No matter the person or their technique, a runner will contact the ground with a force of one and a half to three times their body weight at each step. Ground reaction force is the ground’s response to this impact. It is the vertical component of this impact that is of interest to us – the vertical loading rate.
Vertical loading rates have been repeatedly linked to running overuse injuries in both prospective and retrospective studies. Thus, if we can learn to properly absorb this impact we can help prevent the epidemic of running injuries. This is what popularized many of the running advice we see today. One example of a now somewhat infamous diagram is explained below.
This diagram represents how foot strike can influence the impact of running, and is exactly why the barefoot running and minimalist shoe trend has gone viral. The body has a natural ability to attenuate vertical impact forces and using a forefoot strike method allows these processes to occur (think landing on your forefoot versus your rearfoot when skipping rope). There are a few ways to encourage a mid to forefoot strike when running. The first is to increase your running cadence. An increase in cadence of 5-10% (or a standard 180+/- 10 steps per minute), has been found to encourage a more plantar flexed foot and increased knee bend knee at initial contact, as well as a footstrike pattern more directly under a person’s center of mass.
To assist with some of this biomechanical knowledge transfer, I have included a video analysis of a female runner as a clinical example of how shoes alone can immediately change biomechanics.
The healthy runner in this video was taped in three situations: traditional (PECH) shoes, minimalist shoes, and barefoot.
Traditional (PECH) shoes
Comparison of all three
All videos were taken in succession with no delay for training or even cuing during the process. This will help explain vertical impact can result in pain, and why improved running mechanics are used to absorb these forces. Though minimalist running is not for all runners, and the change to minimalist shoes needs to be taken gradually and with caution, this video highlights how running shoes can effect these changes, and sheds light onto the growing popularity of the minimalist running movement.
Always be sure to consult your physiotherapist before making drastic changes to your running shoes or form.
Amy Fahlman BSc PT, MCl Sc (manip) Fellow of CAMPT
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