Ting - 2007 - Neuromechanics of muscle synergies for posture and movement

Citation

Ting LH, McKay JL. Neuromechanics of muscle synergies for posture and movement. Current Opinion in Neurobiology. 2007 Dec;17(6):622-628. DOI

10 Word Summary

Neural constraints on postural tasks are explained by muscle synergies.

Abstract

Recent research suggests that the nervous system controls muscles by activating flexible combinations of muscle synergies to produce a wide repertoire of movements. Muscle synergies are like building blocks, defining characteristic patterns of activation across multiple muscles that may be unique to each individual, but perform similar functions. The identification of muscle synergies has strong implications for the organization and structure of the nervous system, providing a mechanism by which task-level motor intentions are translated into detailed, low-level muscle activation patterns. Understanding the complex interplay between neural circuits and biomechanics that give rise to muscle synergies will be crucial to advancing our understanding of neural control mechanisms for movement.

Notes

• Muscle synergy - an element from which complex muscle activation patterns are constructed to produce a wide range of motor behaviors.
  • A vector specifying a pattern of relative levels of muscle activation.
• Muscle synergies are directionally tuned to CoM motion.
  • Cats have postural synergies correlated to hind-limb force direction.
• Changes to configuration affect reflexes, proprioception, etc, but synergies are conserved.
• Muscle synergies are likely partially innate and partially learned.
  • Anatomic and physical constraints are likely the reason for this?
  • Plasticity of nervous system allows for learning of new synergies.
• Synergy number is likely the bottleneck for motor efficiency.
• Modeling can help to define the "solution space" afforded by a particular theory, such as the idea of muscle synergies.
• Muscle synergies may help to encode "task-level" variables, obviating the requirement of directly controlling low-level variables such as individual joints.
• Muscle synergies predict a neural constraint observed in experimentally recorded forces of cat hindlimbs during postural tasks.
• There may be a neurological cost to employing many different synergies.