Background: Previous studies have consistently reported that decreasing seat height\nincreases the peak hip and knee joint moments; however, these findings may not\napply to biomechanical changes at very low seat heights. The purpose of this study,\ntherefore, was to examine the effect of a large range of seat heights on peak joint\nmoments of the lower limb during a sit-to-stand (STS) movement.\nMethods: Eight healthy young subjects participated in this experiment. Each subject\nwas instructed to stand up from six seat heights (10, 20, 30, 40, 50 and 60 cm). Joint\nmoments were calculated with an inverse dynamics method. The sum of the hip\nand knee joint moments was used as the index to indicate the mechanical load of\nthe STS movement. The effect of seat height on the mechanical load was examined\nwith both analytical and experimental approaches.\nResults: Through the analytical approach, it was revealed that the mechanical load\nof STS movements from low and normal seat heights (10 to 40 cm) always reaches\nits peak at or near the posture in which the thigh is horizontally positioned. This\nfinding indicates that the peak value is invariant between the low and normal seat\nheights. Similar results were also found in the experimental approach. There were\nfew significant differences in the peak mechanical load and the peak hip and knee\njoint moments between the low and normal seat heights, while they differed\nsignificantly between the low and high seat heights.\nConclusions: This study concluded that, while the peak mechanical load and the peak\nhip and knee joint moments increase inversely to seat height within the range of high\nto normal seat height (60 to 40 cm), they are invariant to the change of seat height\nwithin the range of low to normal seat height (10 to 40 cm). These findings are useful\nfor the design of chair, the improvement in the evaluation standard of minimum sit-tostand\nheight tests and the development of new muscular strength test.
Loading....