Effects of variation in cushion thickness on the sit-to-stand motion of elderly people

This study was done to investigate whether cushion thickness affected elderly people during the sit-to-stand motion (STS motion). Fourteen elderly subjects aged 79 or over were recruited from the outpatients at a rehabilitation clinic. Their STS motions were evaluated and analyzed using a digital video camera and analyzing software. As the thickness of the cushion increased, it was difficult to identify the pelvic movement during STS motion, although the trunk was inclined more anteriorily and the load to the knee extensors was greater. Furthermore, three of the fourteen subjects had difficulties performing STS motion when the pelvis was contoured by a thick cushion. These results suggests that if an older person has a knee extensor strength below an appropriate level and/or the cushion thickness is enough large to contour the subject's pelvis, the risk of falling during STS motion is higher.