Influence of aging and physical frailty of elderly people on the biomechanical characteristics of trunk and lower extremities of sit to stand motion

Abstract

The purpose of this study was to obtain new findings on an effective physical therapy approach to sit-to-stand (STS) motion by clarifying aging- and physical frailty-related changes in kinematic and kinetic characteristics of trunk and lower limbs of elderly people. The subjects were 17 healthy young people, 12 healthy elderly people, and 12 pre-frail elderly people. STS measurements were carried out using a three-dimensional motion analyzer (VICON MX) and ground reaction force plates (AMTI). Furthermore, the moments of the obtained hip, knee and ankle joints were summed to calculate the support moment. In the healthy elderly group, the maximum flexion angle of the trunk was significantly smaller than that in the healthy young group. There was no significant difference between the three groups in terms of the maximum flexion angle of the hip and ankle joint. In the pre-frail elderly group, the maximum flexion moment of the trunk and the hip joint was significantly lower than that of the healthy young group and the healthy elderly group, and the integral value of the extension moment and peak extension moment of the knee joint was significantly higher. Moreover, the ratio of the hip joint extension moment to the support moment was significantly lower than that in the healthy young group and the healthy elderly group, and the ratio of the knee joint extension moment to the support moment was significantly higher. It was suggested that age-related changes occur earlier in trunk movement than lower limb movement. It was also suggested that the absolute value of the kinetic data of the trunk and hip joint during STS motion declines due to the physical frailty of the elderly and that the absolute value of the kinetic data of the knee joint increases to compensate for this physical frailty.