Most recreational and competitive sports impose high levels of force and repetitive stress on the lower extremities. The most common sport-related injuries occur at the foot and ankle. Athletes, therefore, will often benefit tremendously from well-fitted, custom orthotics. Since you have the ability to improve sport performance considerably by providing the right kind of lower extremity support, let's review what goes into a good orthotic for your athletic patients. Whether they are walking or running, playing golf or baseball, or involved in soccer or skating, your active patients need your expert advice regarding custom shoe inserts. CONSTRUCTION MATERIALS The materials used in sport-oriented orthotics have come a long way from the days of steel, leather, and rigid plastic. Now we have carbon fibers, viscoe-lastic polymers, and numerous trade-marked man-made components which are available. Are they really worth the expense? We'll look at some of the most important requirements for a sports orthotic, and see if these new materials are just "gimmicks" or actually useful. Shock absorption. Most of today's sports orthotics are carefully designed to reduce the shock wave which is generated up the leg into the knee, hip, and spine. The addition of carbon fibers helps plastics to flex better, thereby reducing some of the shock sent to the joints. Even better are the viscoelastic polymers, a group of man-made materials specifically created with the purpose of improving on the body's ability to dissipate shock stress to sensitive and easily damaged tissues. Voloshin and Wosk found that viscoelastic shoe inserts significantly reduce the reported pain levels in patients with low back pain.1 A more recent report comes from Denmark, where a control- led study on soccer referees participating in a 5-day tournament found that soreness in the Achilles tendon, calf, and back are significantly reduced by the use of shock absorbing heel inserts? Chronic knee pain due to patellofemoral pain syndrome has also been found to respond well to the use of soft orthotics made with viscoelastic polymers. Weight. In most sports, the amount of weight lifted at each foot lift-off is an important factor in performance.3 A good sport orthotic must, therefore, increase the weight of an athlete's shoe only minimally. The good newer materials are all lighter in weight than the traditional plastics, leather, and cork used previously. Reduced weight is a major reason the carbon fibers and viscoelastic polymers have been so readily accepted by athletes. Good orthotic construction may also take advantage of inventive manufacturing techniques to lose weight, such as holes punched in the material to decrease the density. These "pores" also serve to transmit heat generated during exercise. Comfort. Obviously, fit is a tremendously important factor. A good sport orthotic must be easy to fit into the athlete's shoe, with a minimum of modification. There must never be a sensation of "something in my shoe", which would distract from sports performance. The newer materials seem to be more comfortable and less annoying. There is a much shorter break-in period, and the athlete easily becomes accustomed to sports orthotics constructed from carbon fibers or viscoelastic polymer Per- formance. The best orthotic for an athlete is one which will improve the function of the foot and ankle during complex and strenuous sports endeavors. This means controlling the amount of pronation, supporting the arches, and preventing excessive ankle and calca-neus eversion. Meanwhile, there must be little or no interference in the pro-prioceptive feedback system, and the foot and ankle must be in good balance. The entire foot, ankle, and lower extremity must have excellent mobility to respond immediately to changes in posture and alignment. An orthotic used during sports must be supportive, yet flexible. It has to provide guidance for the foot and ankle, but must not hinder the natural biomechani-cal performance. Torsional rigidity (the ability of the orthotic to resist twisting) combined with longitudinal flexibility (especially at the forefoot) seem to be the major indicators of a good sports orthotic, in my experience. I would characterize such an insert as a firm, yet flexible, orthotic. Durability. Unless you are dealing with a very highly-paid athlete, cost and durability are tightly interwoven considerations. Since athletic endeavors produce higher forces and stresses on an orthotic, it must be capable of sustaining physical insults repeatedly, with no perceptible decrease in performance or shock absorption. Moisture and heat must not cause significant degradation of any of the above factors. Once again, the newer materials are usually the most durable, and when proper care is taken, their physical characteristics can be maintained for a long time. CONCLUSION The newer materials used in most sport orthotics are not just sales gimmicks. They do provide the needed factors of shock absorption, lightweight, comfort, performance, and durability. While the Continued on page 48... ATHLETES AND ORTHOTIC SUPPORT ...from page 39 cost of these materials is somewhat more, the benefits are so much greater. The materials do need to be integrated in an appropriate design with skilled construction, however. Your athletic patients should not settle for lesser orthotics. When you provide your active patients with the properly fitted and selected custom orthotics for their sports, they'll perform better, and your practice will grow by word of mouth. Dr. Mark N. Charrette is a 1980 summa cum laude graduate of Palmer College of Chiropractic. He lectures nationally on chiropractic biomechanics and orthopedics, and has taught more than 150 seminars in the last fifteen years. His articles have appeared in several leading chiropractic journals, including The American Chiropractor and Success Express. Dr. Charrette is currently in practice in Las Vegas, NV. REFERENCES Voloshin A, Wosk J. An in vivo study of low back pain and shock absorption in the human locomotor system. J Biomech 1982; 15:21-7. Fauno P et al. Soreness in lower extremities and back is reduced by use of shock absorbing heel inserts. intJ Sport Med 1993; 14:288-90. Eng JJ, Pierrynowski MR. Evaluation of soft foot orthotics in the treatment of patellofemoral pain syndrome. Phys Ther 1993; 73:62-70.*
