Biomechanics of recumbent cycling: instrumentation, experimentation, and modeling

Abstract

Cycling in the recumbent position has recently become popular. However, very little is known about this position, specifically in regards to the effects of body position and orientation on maximal power output and the energetics of the lower extremity. Three separate experimental investigations were completed in order gain a better understanding of this mode of cycling. In the first investigation, the effects of altering body configuration angle (included angle between mid torso, hip joint, and crank-arm spindle) on maximal-power output were examined while recumbent cycling (hip joint 15° below crank-arm spindle). Power output declined significantly as body configuration angle was reduced from that selected by subjects in the standard, upright cycling position. However, power output in the recumbent cycling position was not reduced compared to the standard cycling position when body configuration angle was matched. In the second investigation, body configuration angle was held constant while the effects of hip orientation angle (hip joint to crank-arm spindle relative to horizontal) on maximal-power output in three different recumbent positions were examined. Hip orientation angle had no effect on power output. Body configuration angle was matched to that selected by the subjects in the standard cycling position. No difference in power output was found between the recumbent and standard cycling positions. In the third investigation, lower-extremity energetics were examined through inverse-dynamics modeling. In order to perform the inverse dynamics, clipless pedals were modified to measure reaction forces as well as pedal and crank-arm angles. While cycling steady state at 90 rpm and 250 W in a recumbent and standard cycling position with matched body configuration angle, simultaneous force-pedal system and lower-extremity joint kinematics were collected. While the kinematics and kinetics were extremely similar, several significant differences were found. Energy transferred across the hip joint from the upper body/pelvis was significantly reduced in the recumbent position. Additionally, work at the knee was redistributed in the recumbent position with more work done during knee flexion and less during knee extension compared to the standard cycling position. These differences may have implications on performance between the two modes of cycling.