Abstract
Objective
This paper aims to analyze the kinetics of the over-ground wheel-type body weight supporting system (BWS); tendency changes of low extremity joint moment (hip, knee, ankle), 3 axis accelerations of a trunk, cadence and gait velocity as weight bearing level changes.
Method
15 subjects (11 males, 4 females, age:23.63.5, height:170.65.1cm, weight:69.0210.75kg) who had no history of surgery participated. 6 levels (0%, 10%, 20%, 30%, 40% and 50%) of BWS were given to subjects at self-selected gait velocity and kinetic data was calculated using a motion capture system, Vicon® (Vicon, UK).
Results
Maximum joint moments at the hip, knee, and ankle decrease as weight bearing increases on the sagittal plane. However, no significant decrease was found after 20% level of BWS at the hip and knee joint. On the other hand, the maximum ankle joint moment keeps decreasing.
The root mean square (RMS) values of the acceleration in three directions: anterior-posterior (AP), medial-lateral (ML), and vertical(V) are analyzed. All 3-dimensional accelerations decrease as BWS increases while there is no significant difference over 20% level of BWS in the ML acceleration. V acceleration is reduced almost by half as soon as BWS level starts, but no further significant decrease can be found after 30% level of BWS. The AP acceleration tends to keep decreasing as BWS level increases.
The cadence and gait velocity with wheel-type BWS decreases as BWS increases.
Discussion
The maximum joint moments of the hip and knee do not significantly decrease when BWS exceeds a certain level, which is different from the case with BWS on treadmill; the maximum moments tend to keep decreasing linearly as BWS level increases on treadmill.
In the case of the hip joint, the maximum moment is generated between toe-off and pre-swing phase, which generates force to push a trunk forward. With higher BWS, forward progression of the trunk is assisted by the wheel rather than driven by the lower extremity. It should be noticed that not only the tendency is different from BWS on treadmill, but the magnitude of the maximum hip moment is smaller than that of BWS on treadmill when BWS level is over 20%.
The maximum knee joint moment is generated at the loading-response phase working as braking and shock absorption during gait, and thus the decrease in the maximum knee moment implies that less braking and shock absorption are required as BWS level increases.
Only the maximum ankle joint torque keeps decreasing as BWS increases. The ankle moment is considered the largest contributor to forward acceleration. The tendency of the maximum ankle moment and the AP acceleration are similar (to what?) as weight bearing proceeds, which implies that walking speed slows down with the wheel-type BWS; the cadence is also reduced as BWS increases.
Conclusion
The results highlight the difference of wheel-type BWS from BWS on treadmill, and provide information on how BWS level affects the joint moment and gait patterns. These outcomes can be utilized as a guideline of gait rehabilitation for people with lower-limb musculoskeletal impairments.
