Muscles have only 2 functions - CONTRACT and RELAX - that's it! If you should lose voluntary control over those 2 functions you lose voluntary control over the result of those functions. Your MOVEMENT! The impulses which signal your muscles to contract and relax come from the Motor Cortex (one half of the Sensory Motor Cortex). So the problem of SENSORY MOTOR AMNESIA is not a structural problem in the muscles but a neurological event in your brain.