A comparison of static and dynamic measures of lower limb joint angles in cycling: application to bicycle fitting

Purpose
Configuration of bicycle components to the cyclist (bicycle fitting) commonly uses static poses of the cyclist on the bicycle at the 6 o’clock crank position to represent dynamic cycling positions. However, the validity of this approach and the potential use of the different crank position (e.g. 3 o’clock) have not been fully explored. Therefore, this study compared lower limb joint angles of cyclists in static poses (3 and 6 o’clock) compared to dynamic cycling.

Methods
Using a digital camera, right sagittal plane images were taken of thirty cyclists seated on their own bicycles mounted on a stationary trainer with the crank at 3 o’clock and 6 o’clock positions. Video was then recorded during pedalling at a self-selected gear ratio and pedalling cadence. Sagittal plane hip, knee and ankle angles were digitised.

Results
Differences between static and dynamic angles were large at the 6 o’clock crank position with greater mean hip angle (4.9 ± 3°), smaller knee angle (8.2 ± 5°) and smaller ankle angle (8.2 ± 5.3°) for static angles. Differences between static and dynamic angles (< 1.4°) were trivial to small for the 3 o’clock crank position.

Conclusions
To perform bicycle fitting, joint angles should be measured dynamically or with the cyclist in a static pose at the 3 o’clock crank position.