ATHLETES

• WHY DEFECTIVE RUNNING SHOES CAN HURT YOU
• SPORT SHOE DESCRIPTION
• HOW TO CHECK FOR MANUFACTURER'S DEFECTS

As trainers and coaches, we know the need for top-notch running equipment we can depend on, namely 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, etc., 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 them away from the sport they 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; i.e., 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’s right for one person
can give another blisters, strained muscles or sore joints. Twenty years ago, buying sneakers meant making sure your toes didn’t 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 athlete’s feet and how they run.
First, find out if their arches are low, normal or high. Have them get their bare feet wet, then ask them to 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 they’re like most people, each of foot 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 a foot excessively rolls in, they 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 they are a pronator if their 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. They may have low arches. Athletes with pronated feet need shoes which emphasize control more than shock absorption.

If their foot excessively turns in (pidgeon-toed), they are a supinator.
Their feet do not absorb shock well. You can tell if they 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. Their arches are probably high. The outside of their foot needs to be supplied with more shock absorption by their shoe so you’ll need a shoe to compensate for this. Either way, their shoe, when placed on a level surface should not be biased in or out. The main purpose behind a running shoe is to hold the foot
stable.

Defective or worn out running shoes which don’t hold feet in a neutral position may accentuate a preexisting biomechanical imbalance (i.e. excessive pronation or supination.) This may lead to unnecessary aches and pains and time off from our beloved sport. A running shoe should be constructed so its upper, midsole and outsole is firmly attached (See Figure1). The upper and heel counter is straight and the sole is straight. The shoe does not rock from side to side. The shock absorbing pockets resist collapsing under load. With this in mind, the following guidelines will help the athlete avoid buying   defective running shoes, and will help prevent injuries.

•The shoe should be glued together securely. Test this by holding the shoe and trying to pull the upper part of the shoe away from the midsole, and the midsole from the outsole (Figure 2). If it separates at all, this will weaken the shoe’s support.
•The upper part of the shoe should be glued straight into the sole. Test this by putting the shoe on a level surface and inspect the back of the shoe (Figure 3A). The whole upper part of the shoe should appear even and should not lean to the right (Figure 3B) or left. A brand new shoe that leans
inwardly or outwardly could cause injuries especially if there is a large asymmetry between each shoe of a pair.
•The sole of the shoe should be level to the surface on which the shoe is resting. Test this by looking to see that the inside and outside of the heel is even to a level surface. (Figure 4A and B). Compare each shoe and from the right to the left shoe for symmetry. An asymmetry of two millimeters can tilt the shoe in or out significantly.
•The shoes should not roll excessively inward and/or outward when resting on a level surface. test this by applying a downward inside, and then a downward outside force to both the right and left shoe to see if they rock inward and/or outward (Figure 5A and B). Check for asymmetry from side to side within each shoe. The shoes should remain even and not roll. If they are new and roll, they will not stop the foot from rolling excessively when worn, and could result in injury.
•Air pockets and gel pockets must be inflated evenly. Test this by pushing on the sides of the air pockets inside to outside, and outside to inside to check for symmetry (Figure 6). Push down into the air pockets both inward
and outwardly from the top of height in the pocket (Figure 7A and B). If the pockets are inflated unevenly, this causes the shoe to collapse unevenly, an the foot to roll when it hits the ground.

Recently, along with a local television investigative reporter, I went to four different sporting goods stores. I randomly chose many pairs of shoes, all of them different brands and styles. From this impromptu sampling, we found a 30-50% defective rate among the shoes we tested. As a board certified physical therapist with three other therapists in my office, there’s not a week that goes by where a patient doesn’t come in with a running injury at least partially related to a shoe with a manufacturer’s defect.
A good running shoe lasts 300-500 miles. Their mileage could be less if their shoes get wet like, when they run in a hot, humid environment; or if they 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. Ask them to put a date somewhere on their shoes so that they know how long they’ve been using them to prevent running on worn out sneakers. Be sure to periodically check their 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 their feet 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’re training for a peak race. However, it’s not unusual for manufacturers to suddenly discontinue shoe models and their 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’ll be broken in, but fresh for the big race.

By the way, a more expensive shoe is not necessarily a better built shoe.
I’ve had many patients come in with injuries due to manufacturer’s defects,
even in the most expensive designer brand running shoes.
My suggestion: Carefully inspect running shoes before your client purchases them. Also, after they’ve purchased the shoes, check them for excessive wear throughout the whole life of the shoe.

by Bruce Wilk, P.T., O.C.S.

WALKING SHOES
Walking shoes should be lightweight and have extra shock absorption in the heel of the shoe, especially under the ball of the foot (the metatarsal area).  this will help reduce heel pain 9plantar faciitis) as well as burning and tenderness in the ball of the foot (metatarsalgia).  Walking shoes have more rigidity in the front in order to roll off of them rather than bend through them as is done with running shoes.

AEROBIC SHOES
Shoes for aerobic conditioning should be lightweight to prevent foot fatigue but also have extra shock absorption in the sole beneath the ball of the foot (metatarsal area) where the most stress occurs.  AOFAS advises working out on carpet vs. concrete.

TENNIS SHOES
Because of the quick side-to-side movements and shifts in weight involved in tennis, tennis players should have a shoe that support the foot accordingly.  A shoe that provides stability on the inside and outside of the foot is an important factor.   Flexibility in the sole beneath the ball of the foot allows for repeated quick forward movement.

BASKETBALL SHOES
Due to the jumping and landing involved with basketball, players should have a shoe with a thick, stiff sole and a high top. It gives extra stability when running as well as when landing.  A high-top shoe provides support to prevent ankle sprains from landing incorrectly.

CROSS TRAINERS
Cross-training shoes combine many of the above features to allow the individual to participate in more than one sport.  A good cross-training shoe should have the flexibility in the forefoot that is necessary for the running combined with the lateral control necessary for aerobic or tennis.  In general, sport more than three times a week; otherwise a cross-trainer should suffice.

Bruce R. Wilk P.T.,O.C.S.
Director of Orthopedic Rehabilitation Specialists, Miami

8720 North Kendall Drive  Suite 206
Miami, Florida  33176
Phone: (305) 595-9425  Fax: (305) 595-8492
E-mail: info@defectiveshoe.com