The validity of an accelerometer-based method for estimating fluidity in the sit-to-walk task in a community setting

[Purpose] Fluidity in the sit-to-walk task has been quantitatively measured with three-dimensional motion analysis system. The purpose of this study was to determine the validity of an accelerometer-based method for estimating fluidity in community-dwelling elderly individuals. [Subjects and Methods] Seventeen community-dwelling elderly females performed a sit-to-walk task. The motion was recorded by an accelerometer, a three-dimensional motion analysis system and a foot pressure sensor simultaneously. The timings of events determined from the acceleration waveform were compared to the timings determined from the three-dimensional motion analysis data (task onset, maximum trunk inclination) or foot pressure sensor data (first heel strike). Regression analysis was used to estimate the fluidity index from the duration between events. [Results] The characteristics of the acceleration waveform were similar to those previously reported in younger adults. Comparisons of event timings from accelerometer and motion analysis system data indicated no systematic bias. Regression analysis showed that the duration from maximum trunk inclination to the first heel strike was the best predictor of fluidity index. [Conclusion] An accelerometer-based method using the duration between characteristic events may be used to precisely and conveniently assess fluidity in a sit-to-walk task in a community setting.