Response of intersegmental knee loads to foot/pedal platform degrees of freedom in cycling

The hypothesis tested in this article was that the three-dimensional intersegmental knee loads would be reduced in cycling by foot/pedal platforms which permitted relative motion between the foot and pedal. To test this hypothesis, pedal load and lower limb kinematic data were collected from 11 subjects who pedaled with four foot/pedal platforms mounted on a six-load-component dynamometer. One of the four platforms did not allow any relative foot/pedal movement while the other three permitted either medial/lateral translation, adduction/abduction rotation or inversion/eversion rotation. Three-dimensional intersegmental knee loads were computed for each of the four platforms using a previously reported biomechanical model. A number of quantities describing each of the intersegmental knee load components was computed and compared using analysis of variance techniques. The key results were that the medial/lateral translation platform did not cause significant differences in intersegmental knee load quantities relative to those for the fixed platform. However, both of the platforms permitting rotations significantly reduced many but did not significantly increase any intersegmental knee load quantities. Of these two platforms, the abduction/abduction platform significantly reduced both the axial and varus/valgus knee moments while the inversion/eversion platform significantly reduced only varus/valgus moments. These results have application to bicycle pedal design where the goal is to reduce intersegmental knee loads, hence possibly alleviating overuse knee injuries.