Biomechanical characteristics of high- and low-frequency trunk acceleration upon gait initiation related to balance ability in community-dwelling elderly people: a cross-sectional study.

Although trunk acceleration during walking is widely used as a measure of stability, few studies have focused on sensitive postural control in community-dwelling elderly people to detect components related to balance ability during gait initiation. This study aimed to clarify the biomechanical characteristics of movement and sensitive postural control related to balance ability, focusing on high- and low-frequency components of trunk acceleration during gait initiation. Healthy older participants were divided into two groups (high-performance older people [Older(H)], n = 11; age, 76.2 ± 3.3 years, and low-performance older people [Older(L)], n = 17; age, 75.8 ± 3.2 years) based on the Timed Up and Go Test time related to balance ability while walking at their chosen speed. Trunk acceleration data were obtained from an accelerometer on the L3-4 level spinous process. The gait velocity was measured at the first step using a motion capture system. The acceleration data were separated into high- and low-frequency components, and the root mean square was calculated. The level of significance was set at 5%. For the high-frequency component, the root mean square of acceleration in Older(L) was significantly lower than that of Older(H) in the mediolateral direction (p = 0.019) and correlated with gait velocity (r = 0.415; p < 0.001). For the low-frequency component, the root mean square of acceleration in Older(L) was significantly lower than that of Older(H) in the vertical (p = 0.034) and anteroposterior direction (p = 0.039). The results suggest that low- and high-frequency components of trunk acceleration can reveal biomechanical characteristics in community-dwelling elderly people.