Find the best shoes for your workout

Cushioning (shock absorption)
Most of the shock on a foot is absorbed through the midsole that spans the length of the shoe (see Diagram 15-1). The thickness of the highly resilient material used for cushioning is generally approximately one inch (2.5 cm) at the heel and a third to half an inch (8 to 13 mm) at the forefoot. The additional thickness at the heel allows for the extra stress created during the heel-strike phase of the gait cycle. It reduces the risk of trauma to the heel and to the Achilles tendon. Some shoes also have a built-in cushioning system on the outer sole, where contact is made with the ground during the running stride. This space-age cushioning has certainly cut down the number of traumatic overuse injuries to runners' feet, particularly in the heel area. Depending on the make and style of the shoe, the cushioning in today's athletic footwear can range from air to water to gel.

Stability
The modern running shoe also features high-tech extra stability devices to improve foot control. The more foot control the shoe offers, the less chance there is of wear-and-tear disorders caused by stressful, repetitive motions. Because of great improvements in the materials used, running shoes can now provide better stability with more motion control. Many insoles have a material on the outside that is harder than in the middle, to help prevent rolling of the foot when it strikes the ground. Much better control of torsion (twisting from the front of the shoe to the back) helps prevent biomechanical abnormalities.

Although running shoes are constantly improving, manufacturers are still having trouble providing maximum stability without sacrificing cushioning properties, and vice versa. Also, stability is often traded off for a lighter-weight shoe, as many runners would rather have the comfort of a lighter shoe than the added stability. If they do not have any foot problems, they can easily get away with this trade-off.

A lot of shoe manufacturers have combined different densities of foam in the midsole to provide greater rigidity in various areas. Firm internal and external heel counters have also been added in some shoes for more rearfoot control. The plethora of new designs is seemingly endless as manufacturers vie for a healthy share of the athletic-footwear market. In the long run, the winner will be the athlete, as the competition will ensure continuous improvements in these shoes.

One of the most important factors determining stability in a shoe is the last. As I mentioned earlier, the last refers to the shape of the sole, and can be compared to the frame of an automobile before the chassis is mounted on it. The two most common types of lasts are straight and curved, and a few rules govern the choice of type. First, if the shape of your foot is basically straight and if you have a low arch, the straight-lasted shoe is best for you, because it offers more support on the inside of the foot and will help prevent you from overpronating, enabling you to minimize overpronation injuries.

If your foot is slightly curved, if you have a higher than normal arch when standing, and if you have been diagnosed as having a rigid foot, you will probably feel more comfortable in curve-lasted shoes. These shoes offer more cushioning but still retain rearfoot stability. People who oversupinate often find that curve-lasted shoes are much better for them because the shape of their feet and that of the shoe are compatible.

If you are uncertain as to which type of last to get, you might want to seek expert advice before buying your next pair of athletic shoes. Many runners, though, can tell whether they require a straight or a curved last just by walking in the shoes for a few minutes.

Flexibility
Flexibility in a running shoe is necessary to take excessive strain off the muscles in the lower leg while you are running. Most flexible shoes today provide better shock absorption than inflexible ones, with little loss in stability. When shopping for a pair of running shoes, you should try bending the shoe in half at the midfoot area. If this cannot be done easily, try another pair. You can also determine flexibility by examining the forefoot outsole patterns on the bottom of the shoe and looking for flex notches on the sides. These patterns and notches are not there for aesthetic purposes; they are designed to provide the required flexibility - most importantly, in the area of the metatarsal heads and toes.

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