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Muscle coordination analysis by time-varying muscle synergy extraction during cycling across various mechanical conditions

Esmaeili Javad, Maleki Ali

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 1

90--99

EN

Central nervous system (CNS) uses the combination of a small number of motor primitives, named muscle synergies, for simplification of motor control in human movement. The aim of this study was to investigate the muscle coordination in both leg muscles during pedaling by time-varying muscle synergy extraction. Twenty healthy subjects performed three 6-min cycling tasks over a range of rotational speed (40, 50, and 60 rpm) and resistant torque (3, 5, and 7 N/M). Surface electromyography signals were recorded during pedaling from eight muscles of the right and left lower limbs. We extracted four time-varying muscle synergies from sEMG patterns. Mean and standard deviation of the quality of the signal reconstruction (R2) for all subjects was obtained 0.9328 ± 0.0120. We investigated the similarity of muscle synergies during cycling across various mechanical conditions. We found the high degrees of similarity (>0.85) among the sets of time-varying muscle synergies across mechanical conditions and also across subjects. Our results show that the same motor control strategies for cycling are used by all subjects in various mechanical conditions.

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Input error analysis of an EMG-driven muscle model of the plantar flexors

de Oliviera L.F., Menegaldo L.L.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 2

75-81

EN

EMG is a useful tool for quantifying muscle forces and studying motor control strategies. However, the relationship between EMG and muscle force is not trivial, and depends in part on muscle dynamics. This work has the following objectives: the first, to find muscle excitations and partial joint torque contribution patterns in isometric plantar flexions, considering low and medium/high contractions. The second, to correlate such patterns with an EMG-driven muscle model error, indirectly assessed by the associate joint torques. Individual muscle contributions were calculated using the model driven by the measured EMG and compared to the total joint torque from dynamometric measurements. Thirteen young males performed a protocol with low and medium/high intensities contractions. Input functions were the normalized EMG of each triceps surae and tibialis anterior muscles. RMS error was calculated between the measured and estimated torque curves. The trends observed were: the order of individual muscle contributions to the total torque (SOL, GM, GL) was different from the order of the contraction intensities (GM, SOL, GL); the model was more accurate for medium/high contractions; the worst estimations occurred when excitation input signals found from EMG were underestimated. Possible causes for such errors and improvement suggestions are addressed.

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Force-Velocity Characteristics of Individual Human Skeletal Muscles: TBCIat and TBCIong. Outline of the Method

Kornecki S., Siemieński A.

International Journal of Occupational Safety and Ergonomics

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1998

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Vol. 4, No. 1

75--83

EN

The aim of the work is to outline a procedure of finding force-velocity (F-V) characteristics (F = f(V)) of individual skeletal muscles of the human locomotor system. The presentation is based on an example concerning extensors of the elbow joint: the lateral and long heads of triceps brachii (TBCIat and TBCIong). The experimental part of the procedure involves a natural movement of using the upper extremity to push an external object of variable, adjustable load, engaging both the elbow and shoulder joint. Five men aged 23 took part in the experiment. Their task was to push the handle of a physical pendulum whose moment of inertia could be adjusted within the range of 58 kg ∙ m2-450 kg ∙ m2, so as to give it maximum angular velocity. During each trial the movement of the trunk, of the upper extremity and of the pendulum was video recorded and the force applied with the hand to the handle of the pendulum was measured. In order to find the F-V characteristics a simulation model SHOULDER was used, which is capable of solving the synergy problem for muscles of the arm and the shoulder girdle. It was found that despite considerable dispersion of experimental points the respective regression lines revealed a clear tendency of decreasing muscle force for increased shortening velocity of the monoarticular head (TBCIat) and of increasing muscle force for increased lengthening velocity of the Particular head (TBCIong) of the triceps brachii muscle.