Sit-to-Walk versus Sit-to-Stand or Gait Initiation : Biomechanical Analysis of Young Men
There are few papers about the biomechanical characteristics of sit-to-walk motion, although many researchers have written about the biomechanical analyses of sit-to-stand motion or gait initiation. The purpose of this study was to compare the biomechanics of sit-to-walk motion with sit-to-stand motion or gait initiation. The subjects were 9 healthy young men, who were instructed to perform sit-to-walk motion, sit-to-stand motion, and gait initiation. Kinematics and kinetics data were obtained using a 3D motion capture system and two force plates. The coordinates of reflective markers (RM)s, the coordinates and velocity of the center of gravity of the whole body (COG), the coordinates and velocity of the center of gravity of the head, arm and trunk (COG of HAT), each joint angle, and the ground reaction forces (GRFs) were calculated from the data. We found that the maximal horizontal velocity of HAT occurred later in a sit-to-walk motion than in sit-to-stand (p<0.05). On the other hand, there was no significant difference of timing between sit-to-walk motion and gait initiation. At the highest point of COG, it moved forward farther in sit-to-walk and moved upward higher in sit-to-stand. Maximal horizontal velocity of COG of HAT before seat-off was significantly higher in the sit-to-walk motion than in the sit-to-stand motion. The peak value of anterior-posterior GRF (Fy) at the heel strike was significantly greater in the sit-to-walk motion than in gait initiation (p<0.05). The COG moved forward over the base of support in the sit-to-walk motion, and then the COG moved forward with one-leg support. These results suggest that sit-to-walk motion is an unstable motion, and requires balance ability to perform. To create an impulsive force, it is important that horizontal velocity of COG of HAT is higher at seat-off in the sit-to-walk motion. Horizontal impulsive force created by HAT movement is suppressed at the first heel strike.
- Journal of physical therapy science
Journal of physical therapy science 18(2), 201-206, 2006-12-30