Distinguishing between stable and unstable sit-to-stand transfers using pressure sensors

The sit-to-stand transfer has been examined in depth using many different methods. Pressure mats and or force plates have been used to partition the transfer into phases. These phases help to identify the beginning and end of the transfer and describe the movement performance, therefore characterizing the transition. The methods of phase breakdown, however, vary depending on the source. In this paper, the objective was to distinguish between a vigorous sit to stand transfer and a slower, less stable sit to stand transfer using a different approach. Ten subjects performed two sit-to-stand transfers each on a hospital mattress, while pressure sensors underneath the mattress gathered movement data. The center of mass was calculated and three features were extracted, then evaluated by a classifier to determine if the features could distinguish between the two movements. Examination of the results determined that two of the three features yielded total accuracy, despite inconsistencies in subject performance. These results suggest that the center of pressure can be used to distinguish between slow, unstable sit-to-stand transfers and vigorous ones. Future work will include the examination of center of pressure in the measurement of balance, as well as the overall assessment of sit-to-stand performance.