Pedal and knee loads using a multi-degree-of-freedom pedal platform in cycling

To provide a scientific basis for the design of bicycle pedals which possibly alleviate over-use knee injuries, two hypotheses were tested in the present study. The two hypotheses were: (1) that the three-dimensional pedal constraint loads; and (2) that the three-dimensional intersegmental knee loads would be reduced more significantly by a foot/pedal platform allowing both adduction/abduction and inversion/eversion rotations simultaneously than by a platform which allowed either rotation individually. To test these hypotheses, pedal load and lower limb kinematic data were collected from 10 subjects who pedaled with four pedal platforms which allowed zero, one, and two degrees of freedom. A number of quantities describing both pedal loads and intersegmental knee loads was computed for each of the four pedal platforms using a previously reported biomechanical model. The quantities included the positive and negative extremes, averages, and areas, as well as the total absolute area and RMS. Quantities were compared using analysis of variance techniques. The key results were that there were significant reductions in the coupled nondriving moments at the pedal for the dual-rotation platform compared to each of the single-rotation cases. The significant reductions in the coupled moments at the pedal were not manifest at the knee. However, a general nonsignificant reduction in both coupled knee moments was evident. Also, the valgus knee moment was significantly reduced by the dual-rotation platform compared to the inversion/eversion only design. Although the axial knee moment was not significantly reduced by the dual-rotation platform over the adduction/abduction design, there was a general nonsignificant reduction. The lack of significance in knee load results occurred because of high intersubject variability. Accordingly, load reduction benefits made by introducing the second degree of freedom need to be considered individually.