Shoe improvements: insoles can provide relief from nagging foot problems

American Fitness, March-April, 2003 by Richard C. Wilson

Today's athletic shoes are scientifically designed to provide most of the features athletes need for comfort, protection and proper biomechanical function. Athletic shoes are basically composed of four parts: the upper, outsole, midsole and insole. The upper is the top of the shoe. The outsole or sole (the portion in contact with the ground) is usually made of a rubber compound. The midsole (the portion of the shoe above the outsole) is the shoe's shock absorber and usually made of ethyl vinyl acetate (EVA). The insole, also called "insert" or "sockliner," is the part inside the shoe on which the foot stands. Although much has been written about athletic shoes, little has been written about what to wear inside them.

When choosing insoles, consider the shoes' original ones first. Usually full-length, removable and made of soft foam, they serve simply as lightweight cushions. Although not very supportive, some athletes find they provide sufficient cushioning, while others routinely remove and replace them. Knowing how to select the right insoles can improve function as well as prevent and help treat injuries. The additional types of insoles available include heel cups, heel pads, arch supports, soft insoles, morthotics and prescription orthotics.

Heel Cups

Heel cups are flexible or rigid devices worn in the shoe's heel area. For example, Tuli's[R] heel cup, is flexible, provides excellent shock absorption and helps prevent as well as treat heel problems, such as plantar fasciitis (i.e., heel tendonitis), heel spurs and bruising (i.e., "stone bruise"). Some flexible heel cups contain a gel to provide more shock absorption (e.g., the Langer PPT Gel Heel Cup). While the MF Heel Cup, the most popular rigid heel cup, is useful for the same conditions as Tuli's[R] heel cup, its mechanism of action differs. Rather than provide direct cushioning, it tightly "squeezes" fat pads beneath the heel together, enhancing the body's own shock absorption. It also stabilizes the heel when the foot strikes the ground, preventing the side-to-side motion that can aggravate a plantar fasciitis condition.

Heel Pads

Primarily shock absorbers, heel pads are flat, soft devices generally made from viscoelastic polymers (e.g., the Viscolas[R] heel pad) or silicone polymers (e.g., the Viscoheel[R]). Some brands also contain a gel that supposedly enhances shock absorption. Although used for the same conditions as heel cups, heel pads are generally less effective.

Arch Supports

Arch supports try to support or elevate the arch and may be full- or three-quarters-length (i.e., extending from the back of the heel to behind the ball of the foot). These over-the-counter devices are primarily useful as shock absorbers, but, depending on their thickness and shape, may also reduce pronation (i.e., rolling in or collapse of the arch). Shock absorption is especially important for fitness instructors. If you don't think your shoes provide adequate shock absorption, the Sorbothane[R] arch support is the best insole for this purpose. Arch supports can also help prevent blisters. Blisters beneath the ball of the foot, caused by abnormal shearing forces, are common among fitness instructors. The Spenco[R] arch support, made of closed-cell neoprene (the same material used in scuba wetsuits), is the best preventive measure for this condition.

Orthotics

The term "orthotic" was formerly used to describe prescription insoles only. Derived from the Greek word orthos, meaning "straight," it implied a "straightening" or correction of a foot imbalance. Although the term is still used to refer to prescription insoles, over-the-counter devices are now frequently called orthotics. Thus, any of the previously mentioned devices may be marketed as an orthotic and are available for under $30 per pair. Prescription orthotics, not needed by most instructors, are considerably more expensive, often costing several hundred dollars.

Morthotics

A device worth mentioning from a point of caution is the "morthotic," or "mail order orthotic." Dr. Peter Cavanagh coined this term in The Running Shoe Book to describe devices ordered by mail. These companies require the buyer to send a tracing of the foot or foam footprint, from which the morthotic will be created. While sometimes effective, these devices offer nothing more than the previously mentioned insoles and can cost over $100.

Prescription Orthotics

Prescription orthotics are a last resort for individuals whose foot problems cannot be controlled with over-the-counter devices. A podiatrist or foot specialist prescribes them after performing a thorough examination and taking an impression of the foot. These devices can be full- or three-quarter-length and made from rigid or soft materials. Softer materials are useful for conditions related to shock, such as shin splints, heel bruising and pain beneath the ball of the foot (i.e., metatarsalgia). Full-length devices are useful for metatarsalgia and other forefoot problems in which additional cushioning is desired. Soft orthotics can be made of leather, cork, foam materials, sponge rubber, EVA (the same material used in midsoles) or shock-absorbing materials, such as Plastazote[R] or Poron[R].