Acceleration driven adaptive filter to remove motion artifact from EMG recordings in Whole Body Vibration

Whole Body Vibration training is more and more utilized in sport medicine to enhance athletic performance and training; recently, vibration treatment is being also used for therapy and rehabilitation for patients affected by different pathologies. It is also worth mention that excessive vibrations can be hazardous. The treatment is based on the hypothesis that under some circumstances vibration loads induce specific responses from the neuromuscular system; some clinical evidences suggest mechanical and metabolic reaction. Usually, vibrations are transmitted by means of a platform oscillating at different frequencies (10-80Hz) to patient body; mainly, limb muscles are involved. Many studies about the subject employ surface EMG recordings to evaluate muscle activity during vibration training. On electrodes, this condition generates large motion artifact at the vibration frequency. To get rid of such artifact an adaptive filter was designed: accelerometers placed onto platform or directly on muscles provide an error signal shape to be cancelled from the raw EMG. In particular, surface EMG have been recorded from leg quadriceps muscles of volunteers during whole body vibration therapy sessions at different oscillating frequency. A standard RLS adaptive filter have been used to cancel the motion artifact from EMG in real-time. Results show the effective cancellations of the vibration frequency from the raw EMG; the RMS value of the cleaned EMG results lower than that unprocessed in some cases up to 50%.