Figure 1

(a) Schematic of 10 Functional Gait Assessment (FGA) tasks: (1) ‘gait on a level surface’, (2) ‘change in gait speed’, (3) ‘gait with horizontal head turns’, (4) ‘gait with vertical head turns’, (5) ‘gait and pivot turn’, (6) ‘step over obstacle’, (7) ‘gait with narrow base of support’, (8) ‘gait with eyes closed’, (9) ‘ambulating backwards’, and (10) ‘steps’ (b) Subjects’ head motion during FGA was recorded using a MEMS sensor attached to their head which comprises three linear accelerometers (recording linear accelerations along the fore-aft, interaural, and vertical axes) and three gyroscopes (recording angular velocity about pitch, roll, and yaw). (c) Asymmetry measures defined as 1) ‘step time asymmetry’, estimated from the time intervals between vertical acceleration peaks for each leg's heel strike was calculated and 2) ‘step length asymmetry’, estimated as the integration of the positive vertical accelerations following heel strike of each leg was calculated. (d) Variability and range of motion were quantified for each of the six axes of head motion as the average of the standard deviation and magnitude of the signal across gait cycles in each task.