Research

The concept for the technology is derived from an in-depth understanding of the biomechanics of gait (walking and running). Dr. D. Casey Kerrigan has been studying walking and running and the effects of footwear over the last two decades first at Harvard Medical School (where she both received her Medical Degree and later invented the Patented architecture and concept). About 12 years ago while at Harvard she showed that high-heeled shoes increase a particular knee torque (force applied at a distance from the knee) that is believed to contribute to the development and progression of knee osteoarthritis. Since that landmark study linking footwear to knee osteoarthritis, she studied the effect of many different types of footwear including men's dress shoes, foot inserts, and athletic shoes. She found that virtually any shoe that has a higher heel than the forefoot increases these detrimental knee torques. She also demonstrated that it does not matter if the heel is firm or heavily cushioned with foams, gels, or plastic shock absorbers. Further, she found that any type of stability or motion control technology, including orthotics and off-the-shelf arch supports, all increase these knee torques.

While much clinical importance has been given to knee joint torques, Dr. Kerrigan found these measurements to be in fact merely the tip of the iceberg in understanding how a shoe can help absorb rather than increase forces throughout the entire body. In studying hundreds of different parameters during walking and running, she found that virtually every current shoe impedes rather than encourages the natural biomechanics of the body. Ideally shoes should work with, not against, the body to reduce forces upward from the foot.

Despite the shortcomings of current shoe design, there remains a scientifically sound basis for providing underfoot a compliant (spring-like) interface between the body and the ground to minimize musculoskeletal wear and tear. Thirty to forty years ago it was demonstrated that a compliant (spring-like) interface between the body and an otherwise hard surface would measurably reduce stresses and strain through the body and when built into an indoor track surface, measurably reduced the incidence of musculoskeletal injuries. This research is not too surprising as we have evolved to walk and run on compliant surfaces, not the concrete and asphalt we typically encounter today. With a compliant surface, the foot pronates and supinates in a natural spring-like fashion in perfect harmony with the compliance in the ground surface.

It has long been assumed that the modern athletic shoe design provides true compliance but in fact, despite all the foams, "air," gels, and plastic struts, none have ever been demonstrated to provide true harmonic compliance during gait. The soles tend to compress prematurely and do not spring back in accordance with the rise and fall of the peak body weight forces. The ineffectual design ends up increasing rather than decreasing forces through the body.

The CDC Suspension System was born as the only solution in a shoe that truly provides compliance comparable to the surfaces we have evolved to walk upon. The System works in harmony, that is, it is coupled to natural, intrinsic foot mechanics to mitigate forces upward from the foot. Rather than inhibiting natural foot motion from supination to pronation and back to supination, the CDC Syspension System actually encourages this motion. Its unique design ensures that compliance is timed perfectly with the rise and fall of the body weight forces. No other shoe has been able to accomplish that. Only the CDC System provides a true, measured compliance during gait helping the body absorb peak forces upward from the foot. In this way, the CDC System provides the biomechanical characteristics expected from walking or running barefoot in a prairie or on a wooded trail. No other shoe can provide that.

Thus while the CDC Suspension System was inspired by dramatic research findings regarding knee joint torques relevant to knee osteoarthritis, the concept is based on a much deeper understanding of human biomechanics and long-term health. Shoes with the CDC Suspension System have been tested in the laboratory and indeed have been found to provide a number of measurable in-vivo attributes beyond minimizing knee (and also hip and ankle) joint torques. For example, they encourage proprioceptive (feedback) signals at initial contact and provide a lowered heel height and broader base of support at landing relevant to stability. And of course, shoes with CDC provide true measurable compliance during gait that indeed is in perfect physiologic harmony with peak body weight forces and joint torques. Finally, a shoe founded in science. A shoe that does everything a shoe should and nothing more.