The relationship of lower limb and trunk movements in sit-to-stand performed by the young and elderly

Abstract

[Purpose] In sit-to-stand, the center of gravity (COG) is transferred from the buttocks to the narrow base of support of the feet, and raising the COG to the standing position is an action with a large dynamic demand, in which the motion of the trunk becomes important for COG transfer. The purpose of this study was to clarify, using young and elderly subjects, how the anterior movement of the trunk (split into trunk and pelvis segments) and lower limb joint movements influence the sit-to-stand action. [Method] Using a 3D motion analysis system and a force plate, we derived the angles of greatest trunk flexion (TA) and pelvic anterior inclination (PA), the fastest speed of center of mass motion (VCM), the absolute angles of the trunk and pelvis segments (TAA and PAA) and the relative angle of the trunk segment to the pelvis (RA) at the moment of buttocks lift-off, as well as the hip and knee joint moments at maximum extension (HM and KM). To find the differences between the actions of the young and the elderly we calculated the correlations between these items. [Results] For the young persons, we found significant negative correlations between KM and TA and RA of maximum flexion, and for the elderly, we found significant negative correlations between KM and TA and PA. In addition, despite the absence of differences in time taken for sit-to-stand, VCM in the forward direction of the elderly was faster than that of the young. [Conclusion] These results suggest the elderly use anterior inclination, and trunk and pelvis flexion to raise the speed of the center of mass (COM) in the forward direction to enable them to raise their COM, whereas the young use anterior inclination of the trunk segment to enable them to raise their COM.