ResPubID20211, Optotrak, accelerometers, gait analysis, gyroscopes, motion measurement, optoelectronic devices, acceleration, feet, gyroscopes, legged locomotion, trajectory, optotrak certus, distal foot rotation, falling risk, foot clearance, foot rotation direction, gait initiation strategies, inertial measurement units, inertial sensor data, motion analysis applications, optoelectronic motion analysis system, sensor noise, toe-off, vertical acceleration