RESULTS: Linear Kinematics

Joint Position. Maximum and minimum horizontal and vertical displacement occurred at relatively the same time during the movement on the recumbent and stationary bicycles. The maximum displacement in the horizontal direction was .23 m while the displacement in the vertical direction was .18 m for the recumbent bicycle; combined, these displacements produced a resultant of .26 m.

On the stationary bicycle, maximum and minimum horizontal and vertical displacement formed on inverse relationship; when horizontal distance increased, vertical distance decreased and vice versa. Maximum horizontal displacement was .12 m and maximum vertical displacement was .32 m. Combined, these displacements produced a resultant of .05 m.

Figure 8. Position of the knee joint in the recumbent bicycle (left) and the stationary bicycle (right). Positions indicate distance from left reference marker. The small dashed line represents horizontal distance; the large dashed line represents vertical distance; the solid line represents resultant distance. Positive slope indicates flexion in the vertical direction on the recumbent bicycle and in the horizontal direction on both bicycles; flexion on the stationary bicycle in the vertical direction is indicated by a negative slope.

Joint velocity. Maximum thigh angular velocity was achieved at the midpoint between the movement from peak extension to peak flexion for both movements on the recumbent and stationary bicycles; values for these velocities were 150 m/s and 136 m/s, respectively. Minimum velocity occurred at the midpoint between peak extension and peak flexion when a change in movement direction was occurring for both movements. Minimum velocities were -150 m/s and -136m/s for the recumbent and stationary bicycles, respectively.

Figure 9. Velocity of the knee joint in the recumbent bicycle (left) and the stationary bicycle (right). Positions indicate distance from left reference marker. The small dashed line represents horizontal distance; the large dashed line represents vertical distance; the solid line represents resultant distance. Positive slope indicates flexion in the horizontal direction on the recumbent bicycle and in the vertical direction on both bicycles; flexion on the stationary bicycle in the horizontal direction is indicated by a negative slope.

Center of mass. The location of the center of mass was calculated from the trunk, thigh and shank segments when the subject was in the initial start position on both the recumbent and stationary bicycles. The center of mass was determined to be in distinctly different locations, the thigh segment and the trunk segment, for the recumbent bicycle and stationary bicycle, respectively. Relative to the knee joint, the subject's center of mass was much closer to this joint in the recumbent bicycle position.

Figure 10. Location of the center of mass (CM) in the recumbent bicycle (left) and the stationary bicycle (right). Segments identified in the figures include: trunk, thigh, shank, and foot.