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Pedal kinetics, including the applied moment (Mz) about an axis orthogonal to the pedal surface and passing through the center of pressure, were measured across three shoe/pedal interface systems (toe-clip and strap, clipless fixed, clipless float) and three workrates (150, 250, 350 W) during steady-state cycling using specially developed multicompatible force pedals. The applied moment (Mz) at the pedal is an important contributor to the corresponding axial moment realized at the knee and has implications for studying overuse injury mechanics and prevention of cycling-related knee pain. Data were collected from 27 knee pain free (KPF) cyclists and 7 cyclists with cycling-related knee pain. The largest applied moments (Mz) were observed when clipless fixed pedals were employed, while clipless float pedals significantly attenuated the applied moment. Cyclists with chronic knee pain exhibited Mz patterns markedly different from the KPF group, supporting the theory that relatively high moments, particularly internally applied moments during the power phase, may be related to knee loads and subsequent overuse injury. Our general conclusion is that clipless pedal float designs quantifiably reduce applied moments at the shoe/pedal interface without compromising power transmitted to the bike.
Jeffrey B. Wheeler is with Biomechanics Research & Consulting, 840 Apollo St., Suite 218, El Segundo, CA 90245. Robert J. Gregor is with the Georgia Institute of Technology, Department of Health & Performance Sciences, Atlanta, GA 30332-0110. Jeffrey P. Broker is with the U.S. Olympic Training Center, Sport Science & Technology Division, One Olympic Plaza, Colorado Springs, CO 80909.