Quantifying Y Balance Test performance with multiple and single inertial sensors

A growing body of evidence has highlighted that inertial sensor data can increase the sensitivity and clinical utility of the Y Balance Test, a commonly used clinical dynamic balance assessment. While early work has demonstrated the value of a single lumbar worn inertial sensor in quantifying dynamic balance control, no research has investigated if alternative (shank) or combined (lumbar and shank) sensor mounting locations may improve the assessments discriminant capabilities. Determining the optimal sensor set-up is crucial to ensuring minimal cost and maximal utility for clinical users The aim of this cross-sectional study was to investigate if single or multiple inertial sensors, mounted on the lumbar spine and/or shank could differentiate young (18-40 years [n = 41]) and middle-aged (40-65 years [n = 42]) adults, based on dynamic balance performance. Random-forest classification highlighted that a single lumbar sensor could classify age-related differences in performance with an accuracy of 79% (sensitivity = 81%; specificity = 78%). The amalgamation of shank and lumbar data did not significantly improve the classification performance (accuracy = 73-77%; sensitivity = 71-76%; specificity = 73-78%). Jerk magnitude root-mean-square consistently demonstrated predictor importance across the three reach directions: posteromedial (rank 1), anterior (rank 3) and posterolateral (rank 6).