Effect analysis of seat height on sit-to-stand movement stability in healthy young adults

Studying the stability of sit-to-stand (STS) could provide a foundation for clinicians when guiding rehabilitation training. The influence of the seat height on STS stability is unclear. The primary goal of this paper was to identify the position of the center of pressure (COP) and the lower limb joint angles during STS movement from different seat heights in order to analyze the relationship between joint angle and COP and understand the influence of seat height on stability during the STS movement. Thirty young volunteers participated in this experiment. The COP offset in the anterior–posterior direction (COP [ap]) and the change in distance of the COP and the center of gravity (COP–COG) were analyzed and compared. The results indicated that seat height has a significant effect on COP at Extension phase (Phase III [p = 0.045]), and COP–COG at the time when the buttocks are about to leave the seat (T1 [p = 0.01]). The stability of STS from the low seat was better than from the high seat. The lower limb joint angles at the time when the hip joint angle reaches its maximum value (T3) and COP (ap) during Phase III were negatively correlated, while lower limb joint angles at the time when the buttocks are about to leave the seat (T1) and COP–COG at the time when the buttocks are about to leave the seat (T1) were positively correlated. The ankle joint angle had more influence than other lower limb joints on STS stability at the time when the buttocks are about to leave the seat (T1).