Analysis of motor units activity to study stiffness modulation in humans

Finding a control method for variable stiffness myoelectric prostheses, which outperforms all others, is still an open topic in research. In this work, the technique of Motor Units decomposition of EMG signals is investigated in order to extract the neural information content transmitted through motor neurons in the form of Motor Units Spike Trains. The hypothesis is that there is a certain co-ordination between the Central Nervous System and Motor Units, which can be detected by coherence analysis of the Cumulative Spike Trains extracted from a pair of antagonistic muscles, and which allows an exclusive signal for stiffness control to be found. This hypothesis is tested with a pilot study by analyzing the EMG signals recorded from the biceps and triceps muscles of a healthy subject during tasks that involve varying the stiffness of the elbow joint.