The effect of robot suit HAL on trunk posture in standing-up movement

Abstract

COP informations and to maximally shift their COP as possible in the anterior and posterior direction. Also, subject was instructed not to raise their toes or heels and to stably maintain their COP position. Each task was performed 3 times in random, with sufficient rest between tasks to prevent fatigue. The maximum COP displacement in 2D directions, the COM displacement in 3D directions, the postural strategy, and the muscle synergy were compared between groups. The COP and COM data were low-pass filtered with a zero-lag, second-order Butterworth filter with a cut-off frequency of 10Hz. The postural strategy during the maximum COP-shift was classified based on Nashner’s three postural strategies. The muscle synergy was identified by an exploratory factor analysis with the principal factor. Results: The maximum COP-shift in the posterior direction decreased significantly in the elderly group compared with the young group. The COMdisplacement in the anterior and posterior direction in the elderly group was significantly smaller than that in the young group. The vertical position of the COM in elders lowered significantly compared with that in youths. Although both group used the hip strategy during the forward COP-shift, the suspensory strategy was more preferred in the elderly group compared with the young group during the backward COP-shift. Factor analysis indicated that the dorsal and ventral muscle groups were involved in the COP-shift. The contributor of postural muscles during the COP-shift differed between the groups. Conclusion(s): This study showed that the vertical postural adjustment was affected by aging, suggesting that the antigravity control may be important to control posture and movement. Implications:Our findings suggest that it may be possible to develop the intervention of physical therapy on neurological rehabilitation (e.g., Stroke, Parkinson disease, SCD and MS).