Understanding recumbent cycling: instrumentation design and biomechanical analysis.

The recumbent cycling position (RCP) is gaining popularity, with both recumbent ergometers and bicycles available as an alternative to the standard, upright cycling position (SCP). However, very little is known about the RCP, creating a situation where uniformed choices are being made. A system was developed for measuring and analyzing the forces placed on a bicycle pedal during operation of a stationary ergometer in either the RCP or SCP. Clipless pedals were modified so that forces normal and tangential to the surface of the pedal could be measured in the plane of the bicyclist. Additionally, the angle of the pedal was measured relative to the crank arm, as well as crank arm angle, so that pedal force orientations in a global reference were known. The pedals were modified in such a way that they were structurally and functionally similar to their original design. After obtaining university-approved informed consent, a single RCP with similar included angle between torso and lower extremities to the SCP was compared by having 19 recreational cyclists pedal in both positions (60 rpm, 250 W). Both pedal forces and lower-extremity kinematics were measured and an inverse-dynamics analysis was performed. The energy transferred from the upper body to the lower extremities was significantly reduced in the RCP. Additionally, the amount of work done by knee flexion was significantly increased in the RCP while total work at the knee was not different. Due to these differences, depending on the situation, it may be more advantageous to select one cycling position over the other.