Cycling with noncircular chainring system changes the three-dimensional kinematics of the lower limbs.

This study investigated the three-dimensional (3-D) pedaling kinematics using a noncircular chainring system and a conventional system. Five cyclists pedaled at their preferred cadence at a workload of 300 W using two crank systems. Flexion/extension of the hip, knee and ankle as well as shank rotation, foot adduction/abduction, and pedal angle were measured. Joint range of motion (ROM) and angular displacements were compared between the systems. Sagittal plane ROM was significantly greater (P < 0.05) at the hip (noncircular system = 39 +/- 3 degrees; conventional system = 34 +/- 4 degrees) the knee (noncircular system = 69 +/- 4 degrees; conventional system = 57 +/- 10 degrees), and ankle (noncircular system = 21 +/- 2 degrees; conventional system = 19 +/- 4 degrees) resulting in greater pedal ROM (noncircular system = 43 +/- 3 degrees; conventional system = 37 +/- 5 degrees) while using the noncircular system. Shank rotation ROM was significantly lower (P < 0.05) while using the noncircular chainring (noncircular system = 10 +/- 1 degree; conventional system = 14 +/- 1 degree). These results support a significant effect of the noncircular chainring system on pedaling kinematics during submaximal exercise.