Viability of Myocontrolled Assistive Technology from a Motor Coordination Perspective

PURPOSE: Current-day rehabilitation often uses myocontrolled assistive technology (AT) in upper limb prostheses or electric wheelchairs. Myocontrol is the control of AT through electromyography (EMG) signals derived from the action potentials produced by the muscles (the myosignals). Since myocontrolled AT often lacks functionality, its viability is critically examined using insights of motor coordination. METHODS: This is a position paper following the style of a narrative review focusing on upper-limb prosthetics. The strategy employed is to take knowledge of motor coordination in the natural situation (i.e., no AT used), and examine whether the requirements of the myosignal in this natural situation meets the requirements of myocontrolled AT. RESULTS: In upper-limb prosthetics myosignals of muscles in the stump are used to control a prosthetic arm/hand system using direct control or via pattern recognition. For both types of control the myosignals need to be accurate regarding movement intent and consistent over repetitions of the same intent. Motor coordination knowledge is used to asses this notions’ viability. First, myocontrol assumes the myosignal to drive the movements. However, muscle activations compensate for external forces. Hence, myosignals have a different role than assumed in myocontrol. Second, myocontrol requires myosignals to be consistent over repetitions. However, due to the abundance of muscles in natural task performance myosignals can be variable over repetitions of performing the same task. DISCUSSION: These insights into natural motor coordination reveal that myosignals might have properties that differ from what is required for good myocontrol. It will be discussed whether exploiting motor coordination principles related to the abundance of muscles in the detection algorithms of myocontrolled AT could improve functionality. CONCLUSION: Myocontrolled AT might be improved when taken into account knowledge of motor coordination.