The Characteristics of Sit-to-stand Movement in Infants Aged 1 Year : A Preliminary Study

Sit-to-stand (STS) movement requires coordinated movement of multiple body segments. However, the kinematic characteristics of STS movement in infants have not been fully clarified. The purpose of this study was to assess the kinematic characteristics of STS movement in infants. Six infants aged 12 to 14 months and 6 adults aged 21 to 22 years old took part in this study. In order to assess STS movement, a motion analysis system consisted of 2 cameras was used. STS movement data which included the duration from initial point to hip off the seat (Phase I) of STS movement and angular movement of each joint (trunk, hip, knee, and ankle) were collected. To compare the sampled data, Mann-Whitney U-test was used. Statistical significance was set at P<0.05. The duration time of Phase I of the infant group significantly increased compared with that of the adult group (P<0.05). The transitional trunk angular movement significantly decreased in the infant group compared with that of the adult group (P<0.05). On the other hand, the transitional hip and ankle angular movement significantly increased in the infant group compared with that of the adult group (P<0.05). These findings suggest that the pattern of STS movement in the infants is characterized by not only less trunk inclination, but also less hip flexion motion and more ankle dorsiflexion. These observed movements exemplify how infants are able to stand from sitting position independently.