Runners seem to have a sixth sense about when they need a new pair of running shoes. Maybe the ankle will start getting that familiar ‘twinge’? Or maybe the knee aches a little more than usual after a long run? Whatever the reason, it’s out with the old and in with new. But before you toss those old Brooks in the garbage and head out to Fleet Feet, lets take a minute and see what secrets your shoes are trying to tell you.
I am of course talking about the wear pattern on the tread of those beloved sneakers. Excessive pronation or under pronation (sometimes called excessive eversion), can lead to compensatory movement patterns further up the leg causing ankle pain, knee pain, and occasionally even hip pain. Wear patterns can tell us a lot about the forces going through your feet while you accelerate and decelerate during a run.
“Force? Acceleration? Wait is this physics? You tricked me!”
Okay, okay. Easy, let me clarifying that I am by no means a physicist. In fact, I have vivid nightmares of sitting in my college physics class praying the answers to the test would come to me through some form of divine intervention. But alas, I feel it is necessary to discuss the principle of force and pressure when talking about tread pattern on our shoes.
Pressure is defined as a force that is applied over a certain area (P = F/A). The greater the force that is applied to a set area, the greater the pressure. Conversely, the smaller the area that a set force is applied to, the greater the pressure. Thus the greatest pressure through the gait cycle is during heel strike and toe off when all of our weight (Force) is placed over the smallest area.
High Pressure = More Wear and Tear. Phew, that’s it. I promise.
In a normal running or walking gait the heel will strike the ground first. This is typically the first spot the tread will wear off on the shoe simply because it is being loaded with the most pressure. Pressure should translate from the outside of the foot, crossing the midline, and finally ending at the big toe as you push off for the next step.
Over pronation means that the foot turns inward when taking a step. Decreasing the area of weight distribution to the inside of the foot creates more inward pressure. Tread is usually worn thin near the inside of the shoe and is preserved on the outside of the shoe. Over pronation can lead to:
Heel pain or plantar fasciitis
Pain in the kneecap
IT band pain syndrome
Low back pain
Under pronation is just the opposite. The area of weight distribution is isolate to the outside of the foot because the foot doesn’t roll in enough when completing the gait cycle. Usually the tread of the big toe will only be minimally worn in comparison to the outside toes. Under pronation can lead to:
Heel pain or plantar fasciitis
Right. Now I assume you are holding your running shoe trying to see what category you fall under and might be feeling a little self-conscious. Don’t worry. Over/under pronation is not the end of the world and there are several options to correcting your running form.
Corrective exercises to strengthen the ankles as well as the hips/gluts will provide the muscle strength to hold your foot in the correct position. Depending on your foot, you may need an orthotic to help distribute your weight to the full area of your shoe. As always, ask your doctor for advice and tips to improve your run.
Oh! And be sure to bring your old running shoes to your appointment. They really do tell quite a story.