Subtask Segmentation of the L Test Using Smartphone Inertial Measurement Units

The L Test of Functional Mobility is used in rehabilitation to assess an individual’s mobility status and dynamic balance. Segmenting subtasks of functional mobility tests can allow clinicians to further identify problematic movements and fall risk for an individual. This research evaluated a rule-based method for L Test subtask segmentation. Twenty able-bodied participants completed five L test trials with a smartphone attached to a belt at their posterior pelvis. A custom-designed walk test app collected accelerometer, gyroscope, and magnetometer data. Smartphone video recordings of each trial were used to determine subtask timing ground truth. A novel segmentation algorithm was developed and attained 97.9% accuracy, 98.5% specificity, and 86.1% sensitivity for stand-up; 94.6% accuracy, 96.2% specificity, and 72.9% sensitivity for sit-down; and 90.8% accuracy, 96.4% sensitivity, and 70.9% specificity for all turns. These experimental results show that the algorithm has potential for use in subtask segmentation of the L Test and should be further assessed on individuals with mobility disabilities.