In normal foot biomechanics the weight-bearing phase of a step is divided into three phases: heel strike, midstance and push-off. At heel strike, the foot is turned outward. Most people will find the greatest wear to be on the outer edge of the heel on their shoes. This is normal. During midstance, as the foot contacts the ground it turns inward or "pronation". Pronation is normal for shock absorption and allows the foot to be "flexible" while it accommodates to variations in the terrain. The foot then moves into supination (weight-bearing on the outer portion of the foot), changing to a "rigid lever" as it prepares for push-off. Push-off is the final phase where body weight is transferred to the ball of the foot. The muscles of the lower leg and foot contract, propelling the body forward as the foot leaves the ground.

Changing your foot biomechanics willfully is difficult. It is much better and easier to provide the appropriate footware, which may include orthotics, for proper support. Abnormal biomechanics most often occurs in midstance. Usually it is either over-pronation or under-pronation. An over-pronated foot has prolonged weight bearing on the inside portion of the foot. It is one that is too flexible and provides little support which can lead to painful shins, knees and hips. An under-pronated foot "supinator" is too rigid and keeps most of the weight on the outside portion of the foot. Fewer problems arise from a supinated foot but can lead to outside ankle or knee pain.

How do you determine what kind of foot you have? Examining your old pair of dress shoes or tennis shoes can give you valuable information on tread wear and provide the easiest way to determine your foot type (pronator, supinator, neutral foot). Look at the heel to see if it is worn on the outside edge. This is normal but we need to look further. Look at the toe or forefoot portion of the sole. This is the critical area. You are a pronator if there is increase wear on the inside edge or big toe area and a supinator with increased wear on the outside edge or little toe area. A neutral foot will have the greastest wear in the midportion of the forefoot. Next do the heel tilt test. Place your shoes next to each other with the heels facing you on a flat-hard surface (your counter-top works best to get at eye-level). Look to see which direction the shoes tilt. Use a pen to help you orient to the perpendicular. A pronator's shoes will tilt toward each other and a supinator's shoes will tilt away from each other. A neutral foot will have no lean or the shoes are too new to tell! Another quick and easy test is the "wet foot test". Place a piece of paper on a hard floor and take a normal step on it with your foot wet. Examine the imprint left by your foot (refer to diagram below and squint for better view). A pronated foot will look almost flat or is flat with the whole foot visible. A supinated foot will have the rearfoot (heel) and forefoot (ball or foot) visible with no line or a small line on the little toe side connecting them. A neutral foot has some curve to it but is not excessive either way.

Getting the perfect shoe to match your foot type should be easier now that you have determined which type you have. All foot types should look for a few basic components. A removable insole is best in case you need to replace it with your own orthotic and is a better arch support than a molded insole. The heel should fit snuggly for better rearfoot control. Be aware of this women if you are purchasing men's shoes. The toe box (front of shoe) should be roomy and allow for you to wiggle your toes comfortably. Wide is better. The toes should not touch the front of the shoe. Your toenails will suffer if not enough room. You should be able to place your first finger in your shoe between your heel and the back of the shoe when sitting, without scrunching your toes. Try on shoes late in the day after your feet have expanded.

Special components for your foot type are generally seen in the last of the shoe. The last is the basic form on which a shoe is built. The upper (fabric) portion of the shoe is placed on a last and a midsole is attached. There are three ways to do this.

1. Board Lasting - The upper portion is glued to a piece of cardboard or fiberboard, making the shoe stiff. This gives good stability but poor shock absorption.
2. Slip Lasting - The upper portion is sewn to the rest of the shoe, like a moccasin, making it flexible. This gives good shock absorption but poor stability.
3. Combination Lasting - The rear of the shoe is board lasted for stability, while the front is sewn for flexibility and cushioning.

Lasting also refers to the curvature of the shoe which is best seen by viewing the sole of the shoe. A straight lasting shoe has no curve and looks like it could be worn on either foot. Almost no shoe is completely straight, so shoes that have a little curvature are called straight. Curve-lasted shoes have a wide angle between the forefoot and rearfoot of the shoe, with the bend toward the big toe side. When you evaluate the last of a shoe look for the degree of curvature it has and take out the insole to tell the type of lasting (board, slip or combination). You will see visible stitches for the slip and combination lasting (in forefoot only).

A pronated foot does best in a shoe with a combination last that is fairly straight with a good arch support and firm midsole. The objective is to find a shoe that prevents the foot from rolling inward excessively. A supinated foot is better in a shoe that has a slip last and is curved with a good arch support and soft midsole. The objective here is to prevent the foot from rolling outward excessively. A neutral foot does best in almost any shoe, but try to avoid an extremely curved shoe that may cause cramping or blisters. Comfort is the primary concern not shock absorption or motion control in a neutral foot. Any good shoe salesperson should help you find a good match for your foot once you know your foot type (pronator, supinator or neutral foot).

A comfortable-properly fitting shoe is the basis to continued participation in exercise while avoiding injury. Don't underestimate the importance of a good match as foot problems can lead to pain from your foot all the way up to your head! It is not uncommon for people suffering from back pain to find the root of their problem due to their foot and improper fitting shoes or lack of custom orthotics for abnormal foot biomechanics. Also, don't keep your shoes forever as they will break down and not support your foot properly. Replace your running shoes every 300-500 miles, walking shoe every 1000 miles and aerobics shoe every 100 hours. Happy Shopping!!!

by Carol Glasscock, MS,PT