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A comparison of four approaches to evaluate the sit-to-stand movementThe sit-to-stand test (STS) is a simple test of function in older people that can identify people at risk of falls. The aim of this study was to develop two novel methods of evaluating performance in the STS using a low-cost RGB camera and another an instrumented chair containing load cells in the seat of the chair to detect center of pressure movements and ground reaction forces. The two systems were compared to a Kinect and a force plate. Twenty-one younger subjects were tested when performing two 5STS movements at self-selected slow and normal speeds while 16 older fallers were tested when performing one 5STS at a self-selected pace. All methods had acceptable limits of agreement with an expert for total STS time for younger subjects and older fallers, with smaller errors observed for the chair (-0.18 ± 0.17 s) and force plate (-0.19 ± 0.79 s) than for the RGB camera (-0.30 ± 0.51 s) and the Kinect (-0.38 ± 0.50 s) for older fallers. The chair had the smallest limits of agreement compared to the expert for both younger and older participants. The new device was also able to estimate movement velocity, which could be used to estimate muscle power during the STS movement. Subsequent studies will test the device against opto-electronic systems, incorporate additional sensors, and then develop predictive equations for measures of physical function.
A pilot study to detect balance impairment in older adults using an instrumented one-leg stance testThe aim of this study was to investigate whether parameters from an instrumented one-leg stance on a force plate test could provide relevant information related to fall risk in older people. Twenty-five community dwelling older people and 25 young subjects performed a one-leg stance while standing on a force plate, with parameters related to transferring weight onto one leg and postural sway in singe-leg stance evaluated. Older participants were classified as being at risk of falling if their performance did not meet one of the previously-established cut-offs for the Five Times Sit-To-Stand and Timed-Up-and-Go tests. Eleven older participants were classified as having a risk of falls. The only significant difference between groups during the weight transfer phase was in the mediolateral displacement, with the fall risk group having less sway than the other groups, signifying a more precautionary approach. With respect to postural sway, both the younger subjects and the no fall risk group stabilised sufficiently to decrease their sway compared to initial values after four and six seconds, respectively. In contrast, the fall risk group was unable to stabilise during the one-leg stance, and continued to sway throughout the 10-sec recording period. These findings suggest that the normal one-leg stance test might not be suitable to detect fall risk. In contrast, an instrumented version of the test could provide valuable additional information that could identify risk of falling in older people.