scholarly journals Human Muscle Synergy Analysis to Approach the Understanding of Brain Control Algorithm

2021 ◽  
Author(s):  
Fereidoun Nowshiravan Rahatabad ◽  
Parisa Rangraz
Keyword(s):  
Control Algorithm ◽  
Functional Unit ◽  
Recurrence Plot ◽  
Human Muscle ◽  
Muscle Synergy ◽  
Hand Movements ◽  
Muscle Synergies ◽  
Emg Signal ◽  
Random Motions ◽  
Non Negative Matrix Factorization

Purpose: Muscle synergy is a functional unit that coordinates the activity of a number of muscles. In this study, the extraction of muscle synergies in three types of hand movements in the horizontal plane is investigated. Materials and Methods: So, after constructing the tracking pattern of three signals, by LabVIEW, the Electromyography (EMG) signal from six muscles of hand was recorded. Then time-constant muscle synergies and their activity curves from the recorded EMG signals were extracted using Non-negative Matrix Factorization (NMF) method. Results: Comparison of these patterns showed that the non-random motions’ synergies were more similar than the random motions among different individuals. It was observed that in all movements, the similarity of the synergies in one cluster was greater than the similarity of their corresponding activation curves. Conclusion: The results showed that the complexity of the recurrence plot in random movement is greater than that of the other movements.

scholarly journals On the Reliability and Repeatability of Surface Electromyography Factorization by Muscle Synergies in Daily Life Activities

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Juri Taborri ◽  
Eduardo Palermo ◽  
Zaccaria Del Prete ◽  
Stefano Rossi
Keyword(s):  
Activity Patterns ◽  
Intraclass Correlation ◽  
Nonnegative Matrix ◽  
Cosine Similarity ◽  
Muscle Synergy ◽  
Coefficient Of Determination ◽  
Muscle Synergies ◽  
Daily Life Activities ◽  
Research Fields ◽  
Emg Signal

Muscle synergy theory is a new appealing approach for different research fields. This study is aimed at evaluating the robustness of EMG reconstruction via muscle synergies and the repeatability of muscle synergy parameters as potential neurophysiological indices. Eight healthy subjects performed walking, stepping, running, and ascending and descending stairs’ trials for five repetitions in three sessions. Twelve muscles of the dominant leg were analyzed. The “nonnegative matrix factorization” and “variability account for” were used to extract muscle synergies and to assess EMG goodness reconstruction, respectively. Intraclass correlation was used to quantify methodology reliability. Cosine similarity and coefficient of determination assessed the repeatability of the muscle synergy vectors and the temporal activity patterns, respectively. A 4-synergy model was selected for EMG signal factorization. Intraclass correlation was excellent for the overall reconstruction, while it ranged from fair to excellent for single muscles. The EMG reconstruction was found repeatable across sessions and subjects. Considering the selection of neurophysiological indices, the number of synergies was not repeatable neither within nor between subjects. Conversely, the cosine similarity and coefficient of determination values allow considering the muscle synergy vectors and the temporal activity patterns as potential neurophysiological indices due to their similarity both within and between subjects. More specifically, some synergies in the 4-synergy model reveal themselves as more repeatable than others, suggesting focusing on them when seeking at the neurophysiological index identification.

Consistency of muscle synergies during pedaling across different mechanical constraints

2011 ◽  
Vol 106 (1) ◽  
pp. 91-103 ◽  
Author(s):  
François Hug ◽  
Nicolas A. Turpin ◽  
Antoine Couturier ◽  
Sylvain Dorel
Keyword(s):  
Neural Control ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Mechanical Constraints ◽  
Relative Contribution ◽  
Lower Limb Muscles ◽  
Emg Patterns ◽  
Mean Variance ◽  
Relative Weighting ◽  
Non Negative Matrix Factorization

The purpose of the present study was to determine whether muscle synergies are constrained by changes in the mechanics of pedaling. The decomposition algorithm used to identify muscle synergies was based on two components: “muscle synergy vectors,” which represent the relative weighting of each muscle within each synergy, and “synergy activation coefficients,” which represent the relative contribution of muscle synergy to the overall muscle activity pattern. We hypothesized that muscle synergy vectors would remain fixed but that synergy activation coefficients could vary, resulting in observed variations in individual electromyographic (EMG) patterns. Eleven cyclists were tested during a submaximal pedaling exercise and five all-out sprints. The effects of torque, maximal torque-velocity combination, and posture were studied. First, muscle synergies were extracted from each pedaling exercise independently using non-negative matrix factorization. Then, to cross-validate the results, muscle synergies were extracted from the entire data pooled across all conditions, and muscle synergy vectors extracted from the submaximal exercise were used to reconstruct EMG patterns of the five all-out sprints. Whatever the mechanical constraints, three muscle synergies accounted for the majority of variability [mean variance accounted for (VAF) = 93.3 ± 1.6%, VAF muscle > 82.5%] in the EMG signals of 11 lower limb muscles. In addition, there was a robust consistency in the muscle synergy vectors. This high similarity in the composition of the three extracted synergies was accompanied by slight adaptations in their activation coefficients in response to extreme changes in torque and posture. Thus, our results support the hypothesis that these muscle synergies reflect a neural control strategy, with only a few timing adjustments in their activation regarding the mechanical constraints.

scholarly journals Is the Neuromuscular Organization of Throwing Unchanged in Virtual Reality? Implications for Upper Limb Rehabilitation

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1495
Author(s):  
Emilia Scalona ◽  
Juri Taborri ◽  
Darren Richard Hayes ◽  
Zaccaria Del Prete ◽  
Stefano Rossi ◽  
...  
Keyword(s):  
Virtual Reality ◽  
Healthy Subjects ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Virtual Reality Environment ◽  
Upper Limb Rehabilitation ◽  
Deceleration Phase ◽  
Research Challenge ◽  
Limb Rehabilitation ◽  
Non Negative Matrix Factorization

Virtual reality (VR) is an appealing approach for increasing the engagement and attention of patients during rehabilitation. Understanding how motor control changes in real vs. virtual scenarios is a research challenge in terms of validating its administration. This study evaluates muscle synergies when subjects conduct throwing tasks in virtual reality. Seventeen healthy subjects performed 20 throws both in a virtual environment and in real one as they threw a ball with both dominant and nondominant arms. The electromyography (EMG) signals of 11 muscles of the upper limbs were recorded. Non-negative matrix factorization was used to extract muscle synergies. The cosine similarity was computed to assess the consistence of muscle synergy organization between virtual and real tasks. The same parameter was used to establish the inter-subject similarity. A three-synergy model was selected as the most likely. No effects of virtual reality and arm side on neuromuscular organization were found. Forearm muscles, not necessary for ball holding and release, were comprised in the activation synergies in the virtual reality environment. Finally, the synergies were consistent across subjects, especially during the deceleration phase. Results are encouraging for the application of virtual reality to complement conventional therapy, improve engagement, and facilitate objective measurements of pathology progression.

Complexity-Based Analysis of the Relation between Human Muscle Reaction and Walking Path

2020 ◽  
Vol 19 (03) ◽  
pp. 2050025 ◽  
Author(s):  
Shahul Mujib Kamal ◽  
Sue Sim ◽  
Rui Tee ◽  
Visvamba Nathan ◽  
Hamidreza Namazi
Keyword(s):  
Fractal Dimension ◽  
Statistical Analysis ◽  
Fractal Theory ◽  
Contact Point ◽  
Fractal Dimensions ◽  
Human Muscle ◽  
Physiological Signals ◽  
Eeg Signal ◽  
Leg Muscles ◽  
Emg Signal

Legs are the contact point of humans during walking. In fact, leg muscles react when we walk in different conditions (such as different speeds and paths). In this research, we analyze how walking path affects leg muscles’ reaction. In fact, we investigate how the complexity of muscle reaction is related to the complexity of path of movement. For this purpose, we employ fractal theory. In the experiment, subjects walk on different paths that have different fractal dimensions and then we calculate the fractal dimension of Electromyography (EMG) signals obtained from both legs. The result of our analysis showed that the complexity of EMG signal increases with the increment of complexity of path of movement. The conducted statistical analysis also supported the result of analysis. The method of analysis used in this research can be further applied to find the relation between complexity of path of movement and other physiological signals of humans such as respiration and Electroencephalography (EEG) signal.

Strategies that simplify the control of quadrupedal stance. II. Electromyographic activity

1988 ◽  
Vol 60 (1) ◽  
pp. 218-231 ◽  
Author(s):  
J. M. Macpherson
Keyword(s):  
Muscle Synergy ◽  
Muscle Synergies ◽  
Electromyographic Activity ◽  
Supporting Surface ◽  
Force Vector ◽  
Tuning Curves ◽  
Hindlimb Muscles ◽  
Vector Generation ◽  
High Level ◽  
Selection Of

1. This study tested the hypothesis that muscle synergies underlie the invariance in the direction of corrective forces observed following stance perturbations in the horizontal plane. Electromyographic activity was recorded from selected forelimb and hindlimb muscles of cats subjected to horizontal translations of the supporting surface in 16 different directions. The responses of muscles were quantified for each perturbation, and tuning curves were constructed that related the amplitude of muscle response to the direction of platform movement. 2. Muscle tuning curves tended to group into one of two regions, corresponding to the two directions of force vectors. A few muscles showed clearly different recruitment patterns. The same direction of correction force vector was produced by different patterns of muscle activity, and the particular EMG pattern depended on the direction of platform movement. Therefore a simple muscle synergy organization could not account for the invariance in force vector generation. 3. It is concluded that there is a hierarchy of control in the maintenance of stance in which the vector of force exerted against the ground is a high level, task-dependent controlled variable and the selection of muscles to activate in order to produce the vector is controlled at a lower level. It is proposed that muscles are controlled using a modified synergy strategy. In this scheme, a synergy is not simply a fixed group of muscles, constrained to act as a unit. Rather, muscles are organized as a task-dependent synergy that is tuned or modified as needed by the addition or subtraction of other muscles.

scholarly journals Muscle Synergies Reliability in the Power Clean Exercise

2020 ◽  
Vol 5 (4) ◽  
pp. 75
Author(s):  
Paulo D. G. Santos ◽  
João R. Vaz ◽  
Paulo F. Correia ◽  
Maria J. Valamatos ◽  
António P. Veloso ◽  
...  
Keyword(s):  
Nonnegative Matrix Factorization ◽  
Nonnegative Matrix ◽  
Human Movement ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Complex Task ◽  
Muscle Coordination ◽  
High Similarity ◽  
Strength Tests ◽  
Power Clean

Muscle synergy extraction has been utilized to investigate muscle coordination in human movement, namely in sports. The reliability of the method has been proposed, although it has not been assessed previously during a complex sportive task. Therefore, the aim of the study was to evaluate intra- and inter-day reliability of a strength training complex task, the power clean, assessing participants’ variability in the task across sets and days. Twelve unexperienced participants performed four sets of power cleans in two test days after strength tests, and muscle synergies were extracted from electromyography (EMG) data of 16 muscles. Three muscle synergies accounted for almost 90% of variance accounted for (VAF) across sets and days. Intra-day VAF, muscle synergy vectors, synergy activation coefficients and individual EMG profiles showed high similarity values. Inter-day muscle synergy vectors had moderate similarity, while the variables regarding temporal activation were still strongly related. The present findings revealed that the muscle synergies extracted during the power clean remained stable across sets and days in unexperienced participants. Thus, the mathematical procedure for the extraction of muscle synergies through nonnegative matrix factorization (NMF) may be considered a reliable method to study muscle coordination adaptations from muscle strength programs.

scholarly journals Sensorimotor feedback based on task-relevant error robustly predicts temporal recruitment and multidirectional tuning of muscle synergies

2013 ◽  
Vol 109 (1) ◽  
pp. 31-45 ◽  
Author(s):  
Seyed A. Safavynia ◽  
Lena H. Ting
Keyword(s):  
Sagittal Plane ◽  
Balance Control ◽  
Center Of Mass ◽  
The Body ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Muscle Coordination ◽  
Initial State ◽  
Sensorimotor Feedback ◽  
Task Level

We hypothesized that motor outputs are hierarchically organized such that descending temporal commands based on desired task-level goals flexibly recruit muscle synergies that specify the spatial patterns of muscle coordination that allow the task to be achieved. According to this hypothesis, it should be possible to predict the patterns of muscle synergy recruitment based on task-level goals. We demonstrated that the temporal recruitment of muscle synergies during standing balance control was robustly predicted across multiple perturbation directions based on delayed sensorimotor feedback of center of mass (CoM) kinematics (displacement, velocity, and acceleration). The modulation of a muscle synergy's recruitment amplitude across perturbation directions was predicted by the projection of CoM kinematic variables along the preferred tuning direction(s), generating cosine tuning functions. Moreover, these findings were robust in biphasic perturbations that initially imposed a perturbation in the sagittal plane and then, before sagittal balance was recovered, perturbed the body in multiple directions. Therefore, biphasic perturbations caused the initial state of the CoM to differ from the desired state, and muscle synergy recruitment was predicted based on the error between the actual and desired upright state of the CoM. These results demonstrate that that temporal motor commands to muscle synergies reflect task-relevant error as opposed to sensory inflow. The proposed hierarchical framework may represent a common principle of motor control across motor tasks and levels of the nervous system, allowing motor intentions to be transformed into motor actions.

Information-based analysis of the relation between human muscle reaction and walking path

2020 ◽  
Vol 28 (6) ◽  
pp. 675-684 ◽  
Author(s):  
Shahul Mujib Kamal ◽  
Norazryana Binti Mat Dawi ◽  
Sue Sim ◽  
Rui Tee ◽  
Visvamba Nathan ◽  
...  
Keyword(s):  
Nervous System ◽  
Information Content ◽  
Muscle Activity ◽  
Human Muscle ◽  
Complex Structures ◽  
Entropy Analysis ◽  
Movement Path ◽  
Leg Muscles ◽  
Emg Signal ◽  
Leg Muscle

BACKGROUND: Walking is one of the important actions of the human body. For this purpose, the human brain communicates with leg muscles through the nervous system. Based on the walking path, leg muscles act differently. Therefore, there should be a relation between the activity of leg muscles and the path of movement. OBJECTIVE: In order to address this issue, we analyzed how leg muscle activity is related to the variations of the path of movement. METHOD: Since the electromyography (EMG) signal is a feature of muscle activity and the movement path has complex structures, we used entropy analysis in order to link their structures. The Shannon entropy of EMG signal and walking path are computed to relate their information content. RESULTS: Based on the obtained results, walking on a path with greater information content causes greater information content in the EMG signal which is supported by statistical analysis results. This allowed us to analyze the relation between muscle activity and walking path. CONCLUSION: The method of analysis employed in this research can be applied to investigate the relation between brain or heart reactions and walking path.

scholarly journals Motor Control System for Adaptation of Healthy Individuals and Recovery of Poststroke Patients: A Case Study on Muscle Synergies

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Fady S. Alnajjar ◽  
Juan C. Moreno ◽  
Ken-ichi Ozaki ◽  
Izumi Kondo ◽  
Shingo Shimoda
Keyword(s):  
Motor Control ◽  
Control System ◽  
Motor Recovery ◽  
Muscle Synergy ◽  
Behavioral Adaptation ◽  
Muscle Synergies ◽  
Healthy Individuals ◽  
Familiar Environment ◽  
Motor Control System ◽  
Healthy Participants

Understanding the complex neuromuscular strategies underlying behavioral adaptation in healthy individuals and motor recovery after brain damage is essential for gaining fundamental knowledge on the motor control system. Relying on the concept of muscle synergy, which indicates the number of coordinated muscles needed to accomplish specific movements, we investigated behavioral adaptation in nine healthy participants who were introduced to a familiar environment and unfamiliar environment. We then compared the resulting computed muscle synergies with those observed in 10 moderate-stroke survivors throughout an 11-week motor recovery period. Our results revealed that computed muscle synergy characteristics changed after healthy participants were introduced to the unfamiliar environment, compared with those initially observed in the familiar environment, and exhibited an increased neural response to unpredictable inputs. The altered neural activities dramatically adjusted through behavior training to suit the unfamiliar environment requirements. Interestingly, we observed similar neuromuscular behaviors in patients with moderate stroke during the follow-up period of their motor recovery. This similarity suggests that the underlying neuromuscular strategies for adapting to an unfamiliar environment are comparable to those used for the recovery of motor function after stroke. Both mechanisms can be considered as a recall of neural pathways derived from preexisting muscle synergies, already encoded by the brain’s internal model. Our results provide further insight on the fundamental principles of motor control and thus can guide the future development of poststroke therapies.

scholarly journals Alterations in upper limb muscle synergy structure in chronic stroke survivors

2013 ◽  
Vol 109 (3) ◽  
pp. 768-781 ◽  
Author(s):  
Jinsook Roh ◽  
William Z. Rymer ◽  
Eric J. Perreault ◽  
Seng Bum Yoo ◽  
Randall F. Beer
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Stroke Survivors ◽  
Activation Patterns ◽  
Force Matching ◽  
Muscle Activation Patterns ◽  
Anterior Deltoid ◽  
Arm Function

Previous studies in neurologically intact subjects have shown that motor coordination can be described by task-dependent combinations of a few muscle synergies, defined here as a fixed pattern of activation across a set of muscles. Arm function in severely impaired stroke survivors is characterized by stereotypical postural and movement patterns involving the shoulder and elbow. Accordingly, we hypothesized that muscle synergy composition is altered in severely impaired stroke survivors. Using an isometric force matching protocol, we examined the spatial activation patterns of elbow and shoulder muscles in the affected arm of 10 stroke survivors (Fugl-Meyer <25/66) and in both arms of six age-matched controls. Underlying muscle synergies were identified using non-negative matrix factorization. In both groups, muscle activation patterns could be reconstructed by combinations of a few muscle synergies (typically 4). We did not find abnormal coupling of shoulder and elbow muscles within individual muscle synergies. In stroke survivors, as in controls, two of the synergies were comprised of isolated activation of the elbow flexors and extensors. However, muscle synergies involving proximal muscles exhibited consistent alterations following stroke. Unlike controls, the anterior deltoid was coactivated with medial and posterior deltoids within the shoulder abductor/extensor synergy and the shoulder adductor/flexor synergy in stroke was dominated by activation of pectoralis major, with limited anterior deltoid activation. Recruitment of the altered shoulder muscle synergies was strongly associated with abnormal task performance. Overall, our results suggest that an impaired control of the individual deltoid heads may contribute to poststroke deficits in arm function.

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