Comparison of Circular and Lever Pedaling: a Modeling Approach

Open Access
Author:
van Werkhoven, Herman
Graduate Program:
Kinesiology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 12, 2008
Committee Members:
  • Philip Martin, Thesis Advisor
  • Stephen Jacob Piazza, Dissertation Advisor
Keywords:
  • joint mechanics
  • modeling
  • pedaling
  • lever
  • circular
  • cycling
  • optimization
Abstract:
The circular bicycle drive system has remained relatively unchanged for a number of years despite many attempts at improved designs. One alternative to the traditional circular system is a design in which the rider produces force by pushing on levers, in an oscillating motion, instead of pushing on cranks following a circular path. The purpose of this study was to compare a traditional circular drive mechanism with a proposed lever pedaling design with respect to human effort required to achieve a power output of 250 W. By means of a computer modeling approach, simulations of circular and lever systems were performed using a dynamic optimization framework. A moment-based cost function was employed as the indicator of human effort needed to generate the 250 W power output. Results of the two systems were compared with respect to the magnitude of the cost function output; and net joint moments at the hip, knee, and ankle needed to produce the required power output. Although the joint ranges of motion for the two systems were similar, the predicted joint moments were higher for the lever system at all lower extremity joints. Consequently, the cost function for the lever system (531 N2„ªm2) was 29% higher than the value for the circular system (413 N2„ªm2). Because of the oscillating nature of the lever action, power transfer from the cyclist to the bicycle does not occur continuously for the lever system as it does with the circular system. Accelerations of the levers were higher than those of the chainring and crank in the circular system. The range of the instantaneous power generated about the crank or chainring axis of rotation was 2.2 times greater for the lever system (1055 W operating range) than the circular system (480 W range). These results indicated the lever system transferred power from the cyclist to the bicycle less effectively than the circular system. It was concluded that a traditional circular propulsion system required less human effort than the lever system proposed in this study to sustain a 250 W power output.