Optimized scoring tool to quantify the functional performance during the sit-to-stand transition with a magneto-inertial measurement unit

Background. Sit-to-stand is used as a qualitative test to evaluate functional performance, especially to detect fall risks and frail individuals. The use of various quantitative criteria would enable a better understanding of musculoskeletal deficits and movement strategy modifications. This quantification was proven possible with a magneto-inertial unit which provides a compatible wearable device for clinical routine motion analysis. Methods: Sit-to-stand movements were recorded using a single magneto-inertial measurement unit fixed on the chest for 74 subjects in three groups healthy young, healthy senior and frail. MIMU data was used to compute 15 spatiotemporal, kinematic and energetic parameters. Nonparametric statistical test showed a significant influence of age and frailness. After reducing the number of parameters by a principal component analysis, an AgingScore and a FrailtyScore were computed. Findings: The fraction of variance explained by the first principal component was 77.48 +/- 2.80% for principal component analysis with healthy young and healthy senior groups, and 74.94 +/- 2.24% with healthy and frail senior groups. By receiver operating characteristic curve analysis of this score, we were able to refine the analysis to differentiate between healthy young and healthy senior subjects as well as healthy senior and frail subjects. By radar plot of the most discriminate parameters, the motion's strategy could be characterized and be used to detect premature functional deficit or frail subjects. Interpretation: Sit-to-stand measured by a single magneto-inertial unit and dedicated post processing is able to quantify subjects musculoskeletal performance and will allow longitudinal investigation of aging population.