Differential use and control of mono- and biarticular muscles

Abstract

Most purposive movements are multi-joint actions in which specific patterns of joint moments are necessary to achieve the required segmental accelerations and to exert the appropriate direction and magnitude of force on the environment. Both human and animal studies suggest that mono- and biarticular muscles have different roles in these complex movements. Monoarticular muscles appear to show simple flexor or extensor activation patterns closely related to the required joint displacements, whereas biarticular muscles often exhibit complex multiple bursts of activity aimed at a fine-regulation of the distribution of net moments over the joints of the limb. Different patterns of activation of mono- and biarticular muscles have been observed during natural movements and in response to sudden perturbations or peripheral afferent inputs. Evidence is provided that the control of mono- and biarticular muscles is based on different processes and different sources of information. Monoarticular muscles may be more rigidly grouped into simple flexor or extensor synergies, whereas biarticular muscle activity may be more flexibly sculpted by motion-related feedback from peripheral afferents. Little is known about where and how the integration between perceptual information and the control of net joint moment is realized.