Automatic Scoring of Chair Sit-to-Stand Test Using a Smartphone

Chair sit to stand tests (CST) are widely used in clinical settings to measure endurance, balance and lower extremity muscle strength. It also allows clinicians to predict falls and cognitive decline in older adults. The current CST measurements are done manually using a timer. The manual CST measurements can be imprecise (often leading to high inter-rater variability), and they ignore what kinematics strategies participants use to stand up and sit back on the chair. In this study, we present a smartphone based automatic CST analysis system. The system has the ability of generating a CST score, and perform cycle by cycle motion analysis. To achieve this, it employs two XGBoost classifiers one for recognising who is taking the test and which chair rising strategy they use. This information is then used to adapt its algorithms for more accurate CST score predictions. The performance of the system was tested on 30 participants including three demographics group (healthy young, healthy adult and Parkinson’s) who were using two different chair rising strategies (flexion and momentum transfer). Overall, the system had above 95% classification accuracy, and the mean absolute difference between predicted and actual CST cycle completion time was less than 60 ms (<10% considering that the average cycle completion time was above 1 s). These results are highly encouraging towards developing a new smartphone-based gait and balance assessment tool that can be used in outdoor settings.