Synchronous Bimanual Movements Performed by Homologous and Non-Homologous Muscles

Synchrony of bimanual wrist movements by 12 normal Ss was compared when homologous muscles (e.g., left and right wrist flexors) and when non-homologous muscles (e.g., left flexors and right extensors) were simultaneously active. Movements of the two limbs were less synchronous and more variable in the non-homologous condition. These data imply the existence of an unitary coupling mechanism which facilitates simultaneous action of homologous muscles of the upper limbs.