Tuesday, March 26, 2013

Most Running Shoes Slow You Down and Increase Risk of Injuries

Research presented at the Annual Meeting of the American Academy of Orthopedic Surgeons (March 19, 2013) and to be published next month (Journal of Strength & Conditioning Research, April 2013) shows that running shoes with thick heels can slow you down. They may also increase your chances of injuring yourself.

Adolescent competitive track athletes ran on a treadmill in heavily padded-at-the-heel sneakers, track shoes or barefoot, at four different speeds.

CHANGING FOOTWEAR CHANGES LANDING: Wearing cushioned heel sneakers caused the runners to land on their heel 70 percent of the time at all speeds. Wearing track shoes caused them to land on their heels less than 35 percent of the time. Running barefoot, they landed on their heels less than 30 percent of the time. Shoes with cushioned heels caused runners to land on their heels, while wearing track shoes or no shoes at all caused a forefoot or mid-foot landing.

HARM FROM HEEL STRIKE: Barefoot runners tend to land on their mid-foot or forefoot. Cushioned heels on running shoes tempt runners to take longer strides, so they land on their heels and smack the ground with a much greater force.

Landing on your heel causes the force of your heel striking the ground to be transmitted with more direct and greater force to your hips and knees. Running in flat-soled shoes that promote a forefoot strike transmits less foot-strike force up your leg to your back and helps to prevent hip and knee damage.

One study reports that running barefoot, in and of itself, is neither good nor bad. The key is to decrease the force of your foot hitting the ground. Running barefoot encourages you to take a shorter stride and hit the ground with less force (Journal of Strength and Conditioning Research, 2012; 26 (8): 2021).

WHY RUNNERS ARE INJURED SO FREQUENTLY: Harvard University evolutionary biologist Dan Lieberman claims that modern running shoes may explain why fifty percent of serious runners are injured at least once a year. He also believes that people with joint replacements of their lower extremities should not run (Nature, January, 2010).

LANDING ON YOUR HEELS: Modern running shoes have features that cause runners to land on their heels with forces of at least three times body weight at six-minute mile pace. The faster a runner runs, the greater the force, which causes stress fractures of the feet and lower legs, shin splints, tears in the fascia on the bottom of the feet, knee and hip pain, tendon and joint damage and more.

LANDING ON YOUR FOREFOOT: Hitting the ground with the heel first generates tremendous force because it stops the foot suddenly and temporarily. On the other hand, landing on the front of the foot allows the foot to keep on moving as the heel is lowered toward the ground to distribute the forces throughout the entire lower leg. For example, drop a pen on the tip of one end. It hits with tremendous force because it stops when it hits the ground and then falls forward. However if the pen were dropped on the side of one end, it would hit the ground with much less force because after hitting on the side of one end, the force would be distributed as the pen falls backward to the other end.

EXCESSIVE PRONATION: In the 1960s doctors thought that the high frequency of running injuries was caused by excessive pronation, a rolling inward of the foot after the heel strikes the ground. They felt that the foot rolled inward toward the arch to dissipate the tremendous heel strike forces.

This, in turn, caused the lower leg to twist inward and they blamed the frequent running injuries on the inward twisting motion of the leg after heel strike. They invented running shoes with special arch supports called orthotics to limit inward rolling and built running shoes with thick heels to cushion some of the shock of the heel hitting the ground. These features increase the likelihood that runners land on their heels. Today the standard treatment for many running injuries is special orthotics and padded heels to help heal running injuries. I have written about and prescribed these features for many of my patients with running injuries.

LESS FORCE WITH FOREFOOT LANDING: Dr. Lieberman felt that if the runners ran barefoot, they would be less likely to land on their heels and therefore would not need to wear shoes with padded heels and orthotics. He has shown in elegant experiments that landing on the front part of the foot reduces the force of the foot strike very significantly.

However, he has no data to show that running injuries can be prevented by running barefoot. He has shown only that modern running shoes tend to encourage a runner to land on his heels, and that heel strike generates more force than front foot strike. Also, many roads have stones and cut glass that can cause injuries, and most runners have such thin skin on the bottom of their feet that they couldn't possibly run barefoot or in thin soled shoes.

TODAY DOCTORS STILL PRESCRIBE ORTHOTICS: Most sports medicine doctors treat many running injuries with running shoes with orthotics and thick heels. Now we have running shoes with very thin soles and minimal heels (such as Vibram Five Fingers or Dunlop Volley). Indeed, Vibram supported Dr. Lieberman's studies.

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