Today I have a great guest piece by Steve Magness examining pronation, motion control, and barefoot running.
The running shoe model needs to be fixed. Pronation, Motion Control, Cushioning, and Stability shoes? Get rid of them all.
It’s not just barefoot running and minimalism versus running shoes, the either/or situation many portray it to be. It’s much deeper than that. It’s not even that running shoe companies are evil and out to make a profit. Shoe companies may be accomplishing the goals they set out for, but maybe the goals their aiming for are not what need to be done. The paradigm that running shoes are built upon is the problem.
Running shoes are built upon two central premises, impact forces and pronation. Their goals are simple, limit impact forces and prevent overprontation. This has led to a classification system based on cushioning, stability, and motion control. The problem is that this system may not have any ground to stand on. Have we been focused on the wrong things for 40+years?
I’ll start with the customary statistic of 33-56% of runners get injured every year (Bruggerman, 2007). That is kind of mind blowing when you think about it. Since there are a ton of injuries going on, let’s look at what shoes are supposed to do.
As said earlier, shoes are built upon the premise that impact forces and pronation are what cause injuries. Pronation, in particular has been constructed as the bane of all runners. We have become inundated with limiting pronation via motion control shoes. The central idea behind pronation is that overpronating causes rotation of the lower leg(i.e. ankle,tibia, knee) putting stress on the joints and therefore leading to injuries. Running shoes are therefore designed to limit this pronation. Essentially, running shoes are developed and designed to put the body in “proper” alignment. But do we really need proper alignment?
This paradigm on pronation relies on two main things: (1)over pronation causes injuries and (2) running shoes can alter pronation.
Looking at the first premise, we can see several studies that do not show a link between pronation and injuries. In an epidemiological study by Wen et al. (1997), he found that lower extremitly alignment was not a major risk factor for marathon runners. In another study by Wen et al. (1998), this time a prospective study, he concluded that “ Minor variations in lower extremity alignment do not appear conclusively to be major risk factors for overuse injuries in runners.” Other studies have reached similar conclusions. One by Nigg et al. (2000) showed that foot and ankle movement did not predict injuries in a large group of runners.
If foot movement/pronation does not predict injuries or is not a risk factor for injuries, then one has to question whether the concept is sound or working…
Looking at the second premise, do shoes even modify pronation? Motion control shoes are designed to decrease pronation through a variety of mechanisms. Most choose to insert a medial post or a similar device. In a study by Stacoff (2001), they tested several motion control shoe devices and found that they did not alter pronation and did not change the kinematics of the tibia or calcaneus bones either. Similarly, another study by Butler (2007) found that motion control shoes showed no difference in peak pronation when compared to cushioning shoes. Lastly, Dixon (2007) found similar results showing that motion control shoes did not reduce peak eversion (pronation) and didn’t change the concentration of pressure.
This is sort of a double whammy on motion control shoes. If excessive pronation does not cause injuries to the degree that everyone thinks, and if motion control shoes don’t even alter pronation, what’s the point of a motion control shoe?
Impact forces are the other major scoundrel of running injuries. The thinking goes like this, the greater the impact force on the lower the leg, the greater stress the foot/leg takes, which could potentially lead to injuries. To combat this fear, running shoes, particular cushioning ones, are to the rescue. Let’s take a look.
The first question is, do cushioning shoes do their job?
Wegener(2008) tested out the Asics Gel-Nimbus and the Brooks Glycerin to see if they reduced plantar pressure. They found that the shoes did their job!….But where it reduced pressure varied highly. Meaning that pressure reduction varied between forefoot/rearfoot/etc. This led to the interesting conclusion that their should be a shift in prescribing shoes to one based on where plantar pressure is highest for that individual person. It should be noted that this reduction in pressure was based on a comparison to another shoe, a tennis shoe. I’m not sure that this is a good control. Basically, this study tells us that cushioned running shoes decrease peak pressure when compared to a Tennis shoe.
In a review on the subject, Nigg (2000) found that both external and internal impact force peaks were not or barely influenced by the running shoes midsole. This means that the cushioning type does not change impact forces much, if at all. But how can this be? I mean it’s common sense if you jumped on concrete vs. jumped on a shoe foam like surface, the shoe surface is softer right? We’ll come back to this question in a minute.
Tomorrow we’ll evaluate the role of impact forces on running performance…