Employing muscular and stability synergies to perform a desired task

Selection of muscle activation pattern to reach a specific goal by considering the complexities of neuromuscular system and the way it overcomes these complications, is of researchers􀂶interest in motor control. One proposed solutionfor resolving thesecomplexities is the concept of simple module (synergies) that the combination of them leads to more complex activities. In the present work, the existence and arrangement of synergies in the lumbar spine are proved. For this purpose, a model with 18-muscles in level L4-L5 is utilized in the static condition. In order to obtaina muscular and stability synergies, muscle activation, which are obtained by exerting moments in 2D and 3D spaces and angular stiffness to the model,are used. The results show that six muscular synergies suffice to be able to reach any point in the moment space. Also, three stability synergies can reconstruct a part of joint angular stiffness space. In addition, the obtained muscular synergies are robust against changes in the amplitude of exerted moment. In this study, it is shown that one can generates any task involves producing determined moment and angular stiffness in the joint, by combining muscular and stability synergies together.