Synergies and end-effector kinematics in upper limb movements


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    When humans perform movements repeatedly, they are never completely the same. This is possible because many degrees of freedom (DOF) of the human motor system are involved when performing a motor action. In most cases, the number of DOF involved exceeds the minimum necessary to complete the motor task at hand. This results in many possible solutions for a given task, which is the so-called redundancy problem. To coordinate these redundant degrees of freedom (DOF), synergies are often proposed. A synergy is defined as the temporary linking of DOF into task-specific units. Kay (1988) described the emergence of a synergy as the first step of a two-step constraining process due to the interactions amongst environment, organism, and task constraints. In the second step, the constraints act on the synergy, resulting in the specific behavior. This two-step process was examined by looking at the influence of task constraints on synergies, on end-effector kinematics, and on both levels concurrently. The first step of the two-step process was assessed using the uncontrolled manifold analysis of joint angle variability and the second step was assessed using end-effector kinematics. The results revealed that task constraints influenced synergies and end-effector kinematics independently. More importantly, the results of both synergy and end-effector level demonstrated that some constraints are mainly involved in the first step of the process, whereas other constraints mainly influence the second step of the process. This suggests that a two-step process is at play to coordinate the redundant DOF.
    Originele taal-2English
    KwalificatieDoctor of Philosophy
    Toekennende instantie
    • Rijksuniversiteit Groningen
    • Bongers, Raoul, Supervisor
    • Bootsma, Reinoud J., Supervisor, Externe Persoon
    • Otten, Bert, Supervisor
    Datum van toekenning6-nov.-2019
    Plaats van publicatie[Groningen]
    Gedrukte ISBN's978-94-034-1924-4
    Elektronische ISBN's978-94-034-1925-1
    StatusPublished - 2019


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