On the relationship between muscle synergies and redundant degrees of freedom in musculoskeletal systems

Reza Sharif Razavian, Borna Ghannadi, John McPhee

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

It has been suggested that the human nervous system controls motions in the task (or operational) space. However, little attention has been given to the separation of the control of the task-related and task-irrelevant degrees of freedom. Aim: We investigate how muscle synergies may be used to separately control the task-related and redundant degrees of freedom in a computational model. Approach: We generalize an existing motor control model, and assume that the task and redundant spaces have orthogonal basis vectors. This assumption originates from observations that the human nervous system tightly controls the task-related variables, and leaves the rest uncontrolled. In other words, controlling the variables in one space does not affect the other space; thus, the actuations must be orthogonal in the two spaces. We implemented this assumption in the model by selecting muscle synergies that produce force vectors with orthogonal directions in the task and redundant spaces. Findings: Our experimental results show that the orthogonality assumption performs well in reconstructing the muscle activities from the measured kinematics/dynamics in the task and redundant spaces. Specifically, we found that approximately 70% of the variation in the measured muscle activity can be captured with the orthogonality assumption, while allowing efficient separation of the control in the two spaces. Implications: The developed motor control model is a viable tool in real-time simulations of musculoskeletal systems, as well as model-based control of bio-mechatronic systems, where a computationally efficient representation of the human motion controller is needed.

Original languageEnglish (US)
Article number23
JournalFrontiers in Computational Neuroscience
Volume13
DOIs
StatePublished - Apr 12 2019
Externally publishedYes

Keywords

  • Fast control
  • Feedback control
  • Motor control
  • Muscle synergy
  • Orthogonal basis vectors
  • Redundant motion
  • Task space
  • Uncontrolled manifold

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Cellular and Molecular Neuroscience

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