On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs
Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist–antagonist (AA) muscle pairs may provide insight...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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Frontiers Research Foundation
2016
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| Online Access: | http://hdl.handle.net/1721.1/100567 |
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| author | Hirai, Hiroaki Miyazaki, Fumio Naritomi, Hiroaki Koba, Keitaro Oku, Takanori Uno, Kanna Uemura, Mitsunori Nishi, Tomoki Kageyama, Masayuki Krebs, Hermano Igo |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering Hirai, Hiroaki Miyazaki, Fumio Naritomi, Hiroaki Koba, Keitaro Oku, Takanori Uno, Kanna Uemura, Mitsunori Nishi, Tomoki Kageyama, Masayuki Krebs, Hermano Igo |
| author_sort | Hirai, Hiroaki |
| collection | MIT |
| description | Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist–antagonist (AA) muscle pairs may provide insight into such transformations, especially for a reference frame in the muscle space. In this study, we examined the AA concept using the following explanatory variables: the AA ratio, which is related to the equilibrium-joint angle, and the AA sum, which is associated with joint stiffness. We formulated muscle synergies as a function of AA sums, positing that muscle synergies are composite units of mechanical impedance. The AA concept can be regarded as another form of the equilibrium-point (EP) hypothesis, and it can be extended to the concept of EP-based synergies. We introduce, here, a novel tool for analyzing the neurological and motor functions underlying human movements and review some initial insights from our results about the relationships between muscle synergies, endpoint stiffness, and virtual trajectories (time series of EP). Our results suggest that (1) muscle synergies reflect an invariant balance in the co-activation of AA muscle pairs; (2) each synergy represents the basis for the radial, tangential, and null movements of the virtual trajectory in the polar coordinates centered on the specific joint at the base of the body; and (3) the alteration of muscle synergies (for example, due to spasticity or rigidity following neurological injury) results in significant distortion of endpoint stiffness and concomitant virtual trajectories. These results indicate that muscle synergies (i.e., the balance of muscle mechanical impedance) are essential for motor control. |
| first_indexed | 2024-09-23T10:09:35Z |
| format | Article |
| id | mit-1721.1/100567 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:09:35Z |
| publishDate | 2016 |
| publisher | Frontiers Research Foundation |
| record_format | dspace |
| spelling | mit-1721.1/1005672022-09-30T19:17:04Z On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs Hirai, Hiroaki Miyazaki, Fumio Naritomi, Hiroaki Koba, Keitaro Oku, Takanori Uno, Kanna Uemura, Mitsunori Nishi, Tomoki Kageyama, Masayuki Krebs, Hermano Igo Massachusetts Institute of Technology. Department of Mechanical Engineering Krebs, Hermano Igo Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist–antagonist (AA) muscle pairs may provide insight into such transformations, especially for a reference frame in the muscle space. In this study, we examined the AA concept using the following explanatory variables: the AA ratio, which is related to the equilibrium-joint angle, and the AA sum, which is associated with joint stiffness. We formulated muscle synergies as a function of AA sums, positing that muscle synergies are composite units of mechanical impedance. The AA concept can be regarded as another form of the equilibrium-point (EP) hypothesis, and it can be extended to the concept of EP-based synergies. We introduce, here, a novel tool for analyzing the neurological and motor functions underlying human movements and review some initial insights from our results about the relationships between muscle synergies, endpoint stiffness, and virtual trajectories (time series of EP). Our results suggest that (1) muscle synergies reflect an invariant balance in the co-activation of AA muscle pairs; (2) each synergy represents the basis for the radial, tangential, and null movements of the virtual trajectory in the polar coordinates centered on the specific joint at the base of the body; and (3) the alteration of muscle synergies (for example, due to spasticity or rigidity following neurological injury) results in significant distortion of endpoint stiffness and concomitant virtual trajectories. These results indicate that muscle synergies (i.e., the balance of muscle mechanical impedance) are essential for motor control. Japan Society for the Promotion of Science. Grants-in-aid for Scientific Research (KAKENHI) (Grant 24360096) Japan Society for the Promotion of Science. Grants-in-aid for Scientific Research (KAKENHI) (Grant 15H03949) 2016-01-04T13:30:58Z 2016-01-04T13:30:58Z 2015-11 2015-05 Article http://purl.org/eprint/type/JournalArticle 2296-4185 http://hdl.handle.net/1721.1/100567 Hirai, Hiroaki, Fumio Miyazaki, Hiroaki Naritomi, Keitaro Koba, Takanori Oku, Kanna Uno, Mitsunori Uemura, Tomoki Nishi, Masayuki Kageyama, and Hermano Igo Krebs. “On the Origin of Muscle Synergies: Invariant Balance in the Co-Activation of Agonist and Antagonist Muscle Pairs.” Frontiers in Bioengineering and Biotechnology 3 (November 24, 2015). en_US http://dx.doi.org/10.3389/fbioe.2015.00192 Frontiers in Bioengineering and Biotechnology Creative Commons Attribution http://creativecommons.org/licenses/by/4.0/ application/pdf Frontiers Research Foundation Frontiers Research Foundation |
| spellingShingle | Hirai, Hiroaki Miyazaki, Fumio Naritomi, Hiroaki Koba, Keitaro Oku, Takanori Uno, Kanna Uemura, Mitsunori Nishi, Tomoki Kageyama, Masayuki Krebs, Hermano Igo On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title | On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title_full | On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title_fullStr | On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title_full_unstemmed | On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title_short | On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs |
| title_sort | on the origin of muscle synergies invariant balance in the co activation of agonist and antagonist muscle pairs |
| url | http://hdl.handle.net/1721.1/100567 |
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