ABSTRACT
Recently the unique functional characteristics of bi-articular muscles have been revealed by means of EMG kinesiological analysis and control engineering analysis. A two-joint limb link mechanism provided with one antagonistic pair of bi-articular muscles passing over two adjacent joints as well as two antagonistic pairs of mono-articular muscles at both end joints could control output forces exerted at the end point of the link mechanism in an arbitral direction with only a single input command signal informing the desired direction. The output force distribution of the limb link mechanism with three pairs of six muscles showed a hexagonal shape, whereas the link mechanism without the paired bi-articular muscles and only with the two pairs of mono-articular muscles showed a tetragonal shape. Configurational characteristics of the hexagonal output force distribution indicated that an individual functionally different effective muscular strength can be evaluated from the output force values of four designated points on the output force distribution line. Such a limb link mechanism could also dissolve contact tasks in order to maintain postural stability. Clinical applications utilizing the unique control properties of bi- articular muscles may shed light on future rehabilitation medicine therapies.