Resources - Injuries

 

 

 

Buying New Shoes

By Jake Kennedy, RPT

A running shoe that fits your foots' needs is very important. For proper comfort and to prevent injury, a match between foot type and the components in a running shoe is ideal. Foot type is divided into three categories; low arch, high arch, and neutral.

The low-arched foot is often termed flat-footed, or "over-pronated." A low-arched foot can be determined by looking at it. However, sometimes a foot will have a normal looking arch off the ground, but when standing, the arch flattens outs. This indicates a functionally flat foot. The word "pronation" is defined as the motion of the foot rolling in. Pronation occurs naturally when walking. It loosens the bones of the foot to adapt to different surfaces and absorb shock. Problems can occur when one pronates too much or at the wrong time. If shoes wear excessively on the inside, it is due to over-pronation. Irregular pronation is the most common cause of foot and lower leg injuries.

The high-arched foot usually has the opposite problem. "Over-supinate" is the motion of the foot rolling to the outside. This locks the bones of the foot up to make it a ridged lever so it can propel the body forward. Supination is normal; however, if one supinates too much, the foot will not disperse forces through normal pronation and more shock is absorbed in the foot, knee, hip and back joints. One who over-supinates will wear shoes down on the outside first, and also may have a tendency to stand with the feet slightly rolled out.

The neutral foot is usually not a problem. If there is a problem, only a trained individual may be able to determine it. The reason is that often the foot compensates for mild to moderate structural deformity, and therefore looks normal. Assuming there is no underlying structural deformity, the neutral foot's shoe should wear evenly.

ANATOMY OF A RUNNING SHOE

SHAPE/LAST

Pick up the shoe and look at the bottom of it. Notice how it curves. This is called the "last." There are three types of lasts: straight, slightly curved and curved. The straighter the shoe, the more support it has. The more curved the shoe, the more mobility it permits.

CONSTRUCTION/LAST

There are also three construction options: board lasting, slip lasting and combination lasting. Board lasting shoes have the greatest stability; slip lasting shoes provide more comfort and flexibility. Combination lasting is a compromise. Combination lasted shoes are slip lasted in the forefoot for flexibility and comfort, but have a board in the rearfoot for stability.

To determine the type of construction, remove the sockliner. Underneath the sockliner will be:

  • A fiber board that runs from the heel to the forefoot (board lasting),
  • A board that extends half-way down the shoe with stitching the rest of the way (combination lasting) or
  • No board at all (slip lasting).

MIDSOLE

The midsole separates the shoe's upper from the outsole. This is the most important part of the shoe because it cushions the foot and plays a major role in controlling excessive foot motion. Midsoles come in three basic materials: EVA, compression molded EVA, and polyurethane. EVA is light and has good cushioning, but it tends to compress and lose its effectiveness while the rest of the shoe has plenty of life. Polyurethane is more dependable than EVA; it is heavier and not nearly as flexible. Many shoe models use polyurethane to reinforce a lighter material.

Most new shoes are made with more than one density of EVA or polyurethane. Greater density means greater firmness, which is good if you over-pronate. Two and three density midsoles are often combined to control foot motion. A contoured midsole gives stability.

OUTSOLE

The harder the rubber compound, the greater its durability and weight. The options in increasing weight are blown rubber, solid rubber and carbon rubber.

HEEL COUNTER

The heel counter is the firm cup built into the rear of the shoe that holds the heel in place and helps to control excessive motion. Most heel counters are made of a durable plastic, which is better than chemical sheet. Also, many are reinforced by a hard plastic ring around the bottom which helps with stability.

Once the foot type has been determined, consider the following when buying a running shoe:

LOW-ARCHED FOOT OR "OVER-PRONATOR"

  • The shape/last should be as straight as possible without being uncomfortable. The curve on the outside is not as important as the curve inside. In general, there will be a slight curve on the inside even in a straight last.
  • Optimal construction should be board lasted. Combination lasted would be your second choice.
  • The midsole should be firm with more than one density (two or three). A contoured midsole is optimal.
  • The outsole should be durable, but this does not directly affect the shoe's stability.
  • The heel counter should be firm with a hard plastic ring around the bottom. It should always be vertical-any inward slant may encourage excessive pronation.
  • Make certain the shoe fits comfortably. Roll your ankles in and out to make sure they give a lot of resistance rolling in. This is what will prevent pronation.

HIGH-ARCHED FOOT OR "OVER-SUPINATOR"

  • The shape/last should be as curved as it can be on the inside keeping the outside as straight as possible. The curve on the inside encourages pronation which is what you want. Make sure it is straight or semi-straight on the outside to help prevent the foot from rolling out.
  • The construction last should be slip lasted. Combination lasting would be a second choice.
  • The midsole should be only mildly firm. Cushioning helps with shock absorption.
  • The outsole should be of durable material, although it does not significantly influence shock absorption.
  • The heel counter should be firm with a hard plastic ring around the bottom. The heel counter should always be vertical-any outward slant will encourage supination.
  • Make certain the shoe fits comfortably. Roll your ankles in and out. You want the shoe to give good resistance against rolling out. Also, they should feel highly cushioned.

NEUTRAL FOOT

  • Shape/last can be determined easily at home by drawing an outline of your foot. Now draw a straight line down from just below the big toe towards the heel.
  • The category of the foot determines the shape of the footwear.
  • A combination last will give the best stability and flexibility.
  • The midsole should be moderately firm.
  • The outsole should be flexible.
  • The heel counter should be firm with a hard plastic ring around the bottom.

GENERAL INFORMATION

  • Enlist a salesperson to find the running shoe that has the qualities needed.
  • Less expensive shoes may not have the quality midsole needed to prevent injuries; however, you don't necessarily need to spend over $100 (as some are priced). A reasonable price range is between $55 and $80.
  • Even though the shoe may look perfectly fine, after so many miles, the midsole compresses and breaks down. This causes more stress to the muscles, tendons, bones and joints.
  • Not wearing shoes into the ground is important. Shoes need to be changed often to prevent injuries. The general rule is that if running over 20 miles per week, shoes should be changed every two or three months. If running under 20 miles per week, changing shoes every three to four months is fine.
  • The heavier the runner, the firmer the midsole needs to be. A soft midsole breaks down too quickly.
  • If you have good luck with a model, stay with it as long as it is available.