Balance Training via Multimodal Biofeedback

We have previously demonstrated that vibrotactile feedback of trunk motion significantly improves balance stability in individuals with vestibular deficits and older adults. Recently we have developed a Mobile Instrument for Motion Instruction and Correction (MIMIC) that enables an expert (i.e. physical therapist) to map his/her movements to a trainee (i.e. patient) in a hands-free fashion. MIMIC comprises an Expert Module (EM) and a Trainee Module (TM). Both the EM and TM are composed of six degree-of-freedom inertial measurement units (IMUs), microcontrollers, and batteries. The TM also has an array of vibrating actuators that provides the user with vibrotactile instructional cues. The expert dons the EM, and his/her relevant body position is computed by an algorithm based on an extended Kalman filter that provides asymptotic state estimation. The captured expert body motion information is transmitted wirelessly to the trainee, and based on the computed difference between the expert and trainee motion, directional instructions are displayed via vibrotactile stimulation to the skin. The trainee is instructed to move in the direction of the vibration sensation until the vibration is eliminated. In a proof-of-concept study, five healthy young subjects were instructed to replicate recorded expert anteriorposterior trunk tilt motion using the aforementioned device with vibrotactile, visual, or combined vibrotactile and visual instructional cues. Preliminary results showed that expert-subject cross-correlation values were maximized and time delays and average position errors were minimized when a 0.5 degree position error threshold and proportional plus half derivative control signal of the angle difference between the expert and subject were used. Subjects had significantly reduced position error when replicating the expert motion with combined vibrotactile and visual instructional cues compared to visual instructional cues alone, and slightly reduced error compared to vibrotactile cues alone