As runners and triathletes, we know we need top-notch running equipment we can depend on, namely our athletic footwear. We also know that if there are defects in those shoes such as crooked heel counters, loosely glued midsoles, underinflated shock absorbing pockets, and so on, our chances for injury will increase. This article will explain why running shoes with manufacturer's defects and excessive mileage can physically hurt runners, and ultimately take you away from the sport you love.
When we run, the lower extremity absorbs three to five times our body weight with every heel strike. The gait cycle consists of a stance phase and a swing phase. Most, if not all, overuse injuries occur during the stance phase. The stance phase consists of heel strike, mid-stance and push-off.
At heel strike, the foot initially contacts the ground in a supinated (locked) position. As the foot continues to contact the ground during mid-stance, it pronates (rolls in) to absorb shock (body weight), and adapts to the ground's contour becoming a mobile adapter. During the push-off phase, the foot supinates (rolls out) again to become a rigid lever, and propel the body forward. So in essence, the foot initially coils to absorb the body's weight then recoils to propel the body onto the other lower extremity.
The way people run varies considerably. A shoe that is right for one person can give another blisters, strained muscles or sore joints. Twenty years ago, buying sneakers meant making sure your toes did not jam against the toe box. Because today's running shoes tend to be somewhat customized, it pays to know your feet before you shop.
To select the right shoe, you'll need to know something about your feet and how they run. First, find out if your arches are low, normal or high. Get your bare feet wet, then step on and off a piece of cardboard placed on a hard floor. A foot with a low arch, very little or virtually no arch "indentation" is visible. Nearly the entire bottom of the footprint will be on the floor. On a print made by a high arch, the indentation is very deep, as very little of the arch touches the floor. It may appear C-shaped. The print made by a foot with a normal arch is somewhere between that made by a low and high arch.
If you are like most people, each of your feet goes through the following motions about 600 times per mile: lands on the outside back of the heel; rolls inward (pronation) and flattens out as you move forward, absorbing much of the impact; rolls through the ball and rotates back outward (supination); pushes off.
If your foot excessively rolls in, you are a pronator. Athletes who have pronated feet tend to roll inward throughout the lower extremity. They also tend to have a more supple shock absorbing foot. The drawback to this type of foot is that more power will be necessary during push off. You will know if you are a pronator if your old shoes are deformed, tilting inward. The arch side of the midsole will be compressed. There will be extensive wear at the outside of the heel and at the inside of the forefoot. You may have low arches. Athletes with pronated feet need shoes which emphasize control more than shock absorption.
If your foot excessively turns in (pidgeon-toed), you are a supinator. Your feet do not absorb shock well. You can tell if you are a supinator if an old pair of shoes tilt to the outside. The outside of the midsole will be compressed and soles will be worn along the outer edges. Your arches are probably high. The outside of your foot needs to be supplied with more shock absorption by your shoe so you will need a shoe to compensate for this.
Either way, your shoe, when placed on a level surface should not be biased in or out. The main purpose behind a running shoe is to hold your foot stable. Defective or worn out running shoes which do not hold your feet in a neutral position may accentuate a preexisting biomechanical imbalance (that is, excessive pronation or supination). This may lead to unnecessary aches and pains and time off from our beloved sport.
With this in mind, the following guidelines will help you avoid buying defective running shoes and will help prevent injuries.
A good running shoe lasts 300-500 miles. Your mileage could be less if your shoe gets wet like, when you run in a hot, humid environment; or if you get caught in the rain. The average runner who runs 30 miles a week with normal wear and tear can expect to have a shoe life of about 10-15 weeks. Put a date somewhere on your shoes so that you are sure to know how long you have been using them to prevent running on worn out sneakers. Be sure to periodically check your shoes for signs of premature wear as shoes that are out of alignment can no longer keep your foot and leg in a neutral position.
If a shoe tilts inward it will have a tendency to cause your foot to pronate more than necessary throughout the stance phase. This could lead to injuries such as shin splints, patellar tendonitis at the knee, and iliotibial friction syndrome in the thigh region. If a shoe tilts out, it may prevent pronation and prolong supination. This may lead to stress fractures in the foot and leg as well as anterior knee pain. Either way, the results may be disastrous to your training program.
Long distance runners know that mileage increases dramatically while they are training for a peak race. However, it is not unusual for manufacturers to suddenly discontinue shoe models and you will find your trusty shoe is unavailable for the big race. Therefore, it makes sense to buy an extra pair before a long training program. Check the shoes for defects. Then, put on 40 to 50 dry miles on the shoes, and put them away in the closet. They will be broken in, but fresh for the big race.
By the way, a more expensive shoe is not necessarily a better built shoe, so carefully inspect running shoes before you purchase them. Also, after purchasing the shoes, check them for excessive wear throughout the whole life of the shoe.
How to check for manufacturer's defects
Run The Planet thanks the Defective Shoe website (www.defectiveshoe.com) for the permission to reprint the article "Why defective shoes can hurt you" by Bruce Wilk, Director of Orthopedic Rehabilitation Specialists. Text and illustrations © by Defective Shoe.