Pilot study on quantitative assessment of muscle imbalance: Differences of muscle synergies, equilibrium-point trajectories, and endpoint stiffness in normal and pathological upper-limb movements

Oku, Tatsuo; Uno, Kanna; Nishi, Tomoki; Kageyama, Masayuki; Phatiwuttipat, Pipatthana; Koba, Keitaro; Yamashita, Yuto; Murakami, Kenta; Uemura, Mamoru; Hirai, Hiroaki; Miyazaki, Fumio

doi:10.1109/embc.2014.6944942

Cited by 3 publications

(3 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The physics-based approach is a powerful way to reverse engineer the control mechanism underlying the neuromusculoskeletal system in the dynamic environment. For more details on muscle synergies based on the AA concept, refer also to our recent publications (Koba et al, 2014 ; Oku et al, 2014 , 2015 ; Uno et al, 2014 ).…”

Section: Discussionmentioning

confidence: 99%

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs

Hirai

Miyazaki

Koba

et al. 2015

Front. Bioeng. Biotechnol.

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs

Hirai

Miyazaki

Koba

et al. 2015

Front. Bioeng. Biotechnol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…We found that muscle activities during upper limb reaching movements by healthy subjects are represented by three invariant functional synergies [9]. Moreover, the muscle synergies and endpoint stiffness of the reaching movement in a post-stroke subject were different from those of a healthy subject [10]. However, the examined motor tasks were limited to simple reaching movements, and our muscle synergy analysis has not been validated by comparison with conventional mechanical perturbation method in post-stroke subjects.…”

Section: Introductionmentioning

confidence: 89%

A feasibility study to assess intralimb coordination in stroke rehabilitation: two indices of mechanical impedance by coactivation of agonist muscles

Oku

Uno

Nishi³

et al. 2015

2015 IEEE International Conference on Rehabilitation Robotics (ICORR)

Self Cite

View full text Add to dashboard Cite

Stroke rehabilitation requires intralimb coordination to achieve natural movement after recovery. Focusing on mechanical impedance by the coactivation of agonist muscles, we performed two experiments to assess the intralimb coordination of a post-stroke subject using two indices of the endpoint stiffness and muscle synergies. The results of the first experiment showed that the endpoint stiffness of a post-stroke subject during posture maintenance estimated from muscle synergy analysis resembled that estimated from the mechanical perturbation method. Based on the validity of proposed muscle synergy analysis shown in the first experiment, the results of the second experiment revealed that muscle activities of both the post-stroke and healthy subjects are composed of three muscle synergies in the circle-tracing task. These muscle synergies were invariant despite being determined from time-variant muscle activities; muscle synergies of the post-stroke subject before rehabilitation were different from those of the healthy subject. In addition, the muscle synergies of the post-stroke subject after rehabilitation resembled those of the healthy subject. It is assumed that the post-stroke subject regained appropriate muscle synergies (i.e., the balance of mechanical impedance) after rehabilitation. This study tested the feasibility for practical uses in the assessment, diagnosis, and interventions for stroke rehabilitation using two indices of muscle synergies and endpoint stiffness.

show abstract

“…The physics-based approach is a powerful way to reverse engineer the control mechanism underlying the neuromusculoskeletal system in the dynamic environment. For more details on muscle synergies based on the AA concept, refer also to our recent publications (Koba et al, 2014;Oku et al, 2014Oku et al, , 2015Uno et al, 2014).…”

Section: Physics-based Approach To Muscle-synergy Extractionmentioning

confidence: 99%

Applications of Synergies in Human Machine Interfaces

Vinjamuri¹,

Mao²,

Maybhate³

2019

Frontiers Research Topics

View full text Add to dashboard Cite

Application of neural machine interface in individuals with chronic hemiparetic stroke is regarded as a great challenge, especially for classification of the hand opening and grasping during a functional upper extremity movement such as reach-to-grasp. The overall accuracy of classifying hand movements, while actively lifting the paretic arm, is subject to a significant reduction compared to the accuracy when the arm is fully supported. Such a reduction is believed to be due to the expression of flexion synergy, which couples shoulder abduction (SABD) with elbow/wrist and finger flexion, and is common in up to 60% of the stroke population. Little research has been done to develop methods to reduce the impact of flexion synergy on the classification of hand opening and grasping. In this study, we proposed a novel approach to classify hand opening and grasping in the context of the flexion synergy using a wavelet coherence-based filter. We first identified the frequency ranges where the coherence between the SABD muscle and wrist/finger flexion muscles is significant in each participant, and then removed the synergy-induced electromyogram (EMG) component with a subject-specific and muscle-specific coherence-based filter. The new approach was tested in 21 stroke individuals with moderate to severe motor impairments. Employing the filter, 14 participants gained improvement in classification accuracy with a range of 0.1 to 14%, while four showed 0.3 to 1.2% reduction. The remaining three participants were excluded from comparison due to the lack of significant coherence, thus no filters were applied. The improvement in classification accuracy is significant (p = 0.017) when the SABD loading equals 50% of the maximal torque. Our findings suggest that the coherence-based filters can reduce the impact of flexion synergy by removing the synergy-induced EMG component and have the potential to improve the overall classification accuracy of hand movements in individuals with poststroke flexion synergy.

show abstract

Pilot study on quantitative assessment of muscle imbalance: Differences of muscle synergies, equilibrium-point trajectories, and endpoint stiffness in normal and pathological upper-limb movements

Cited by 3 publications

References 9 publications

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs

On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs

A feasibility study to assess intralimb coordination in stroke rehabilitation: two indices of mechanical impedance by coactivation of agonist muscles

Applications of Synergies in Human Machine Interfaces

Contact Info

Product

Resources

About