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.

Strategies that simplify the control of quadrupedal stance. I. Forces at the ground

1988 ◽  
Vol 60 (1) ◽  
pp. 204-217 ◽  
Author(s):  
J. M. Macpherson
Keyword(s):  
Horizontal Plane ◽  
Center Of Mass ◽  
Area Under The Curve ◽  
Lateral Force ◽  
Polar Coordinates ◽  
Polar Coordinate System ◽  
Dependent Manner ◽  
Supporting Surface ◽  
Force Vector ◽  
Tuning Curves

1. Postural reactions were studied in six cats subjected to small, linear translations of the supporting surface in each of 16 different directions in the horizontal plane. Directions were specified in a polar coordinate system, with posterior translations being 0 degrees and leftward translations, 90 degrees. The data consisted of the forces exerted by each paw of the cat against the ground, measured in three orthogonal directions, vertical (z-axis), longitudinal (y-axis), and lateral (x-axis). 2. The force traces were analyzed by measuring the area under the curve during the postural reaction and dividing by the time of integration to give an average change in force. These values were normalized and plotted against direction of translation in polar coordinates, to give force tuning curves. The longitudinal and lateral force components were combined to generate force vectors in the horizontal plane. 3. Every cat responded to the platform translations with the same, simple strategy in which each hindlimb actively produced a correction force vector in one of only two possible directions. Participation of the forelimbs in the horizontal plane correction was not obligatory. While the direction of each hindlimb force vector was invariant, the amplitude was modulated according to the direction of platform movement. The resultant force vector, that acts through the center of mass of the animal, was in a direction opposite to the platform movement and directly opposed the perturbation. By this strategy, the cat was able to correct for destabilizing movements of the supporting surface in any direction in the horizontal plane. 4. It is concluded that the generation of forces between the paws and the ground is a high-level parameter that is controlled by the nervous system in a task-dependent manner. By using the strategy of restricting these forces to a set of two direction-invariant vectors, the problem of maintaining stance in the face of horizontal plane disturbances is greatly simplified.

EMG Responses to Maintain Stance During Multidirectional Surface Translations

1998 ◽  
Vol 80 (4) ◽  
pp. 1939-1950 ◽  
Author(s):  
Sharon M. Henry ◽  
Joyce Fung ◽  
Fay B. Horak
Keyword(s):  
Postural Control ◽  
Lower Limb ◽  
Maximal Activity ◽  
Erector Spinae ◽  
Muscle Synergy ◽  
Trunk Muscles ◽  
Electromyographic Activity ◽  
Dependent Manner ◽  
Tuning Curves ◽  
Perturbation Direction

Henry, Sharon M., Joyce Fung, and Fay B. Horak. EMG responses to maintain stance during multidirectional surface translations. J. Neurophysiol. 80: 1939–1950, 1998. To characterize muscle synergy organization underlying multidirectional control of stance posture, electromyographic activity was recorded from 11 lower limb and trunk muscles of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. The latency and amplitude of muscle responses were quantified for each perturbation direction. Tuning curves for each muscle were examined to relate the amplitude of the muscle response to the direction of surface translation. The latencies of responses for the shank and thigh muscles were constant, regardless of perturbation direction. In contrast, the latencies for another thigh [tensor fascia latae (TFL)] and two trunk muscles [rectus abdominis (RAB) and erector spinae (ESP)] were either early or late, depending on the perturbation direction. These three muscles with direction-specific latencies may play different roles in postural control as prime movers or as stabilizers for different translation directions, depending on the timing of recruitment. Most muscle tuning curves were within one quadrant, having one direction of maximal activity, generally in response to diagonal surface translations. Two trunk muscles (RAB and ESP) and two lower limb muscles (semimembranosus and peroneus longus) had bipolar tuning curves, with two different directions of maximal activity, suggesting that these muscle can play different roles as part of different synergies, depending on translation direction. Muscle tuning curves tended to group into one of three regions in response to 12 different directions of perturbations. Two muscles [rectus femoris (RFM) and TFL] were maximally active in response to lateral surface translations. The remaining muscles clustered into one of two diagonal regions. The diagonal regions corresponded to the two primary directions of active horizontal force vector responses. Two muscles (RFM and adductor longus) were maximally active orthogonal to their predicted direction of maximal activity based on anatomic orientation. Some of the muscles in each of the synergic regions were not anatomic synergists, suggesting a complex central organization for recruitment of muscles. The results suggest that neither a simple reflex mechanism nor a fixed muscle synergy organization is adequate to explain the muscle activation patterns observed in this postural control task. Our results are consistent with a centrally mediated pattern of muscle latencies combined with peripheral influence on muscle magnitude. We suggest that a flexible continuum of muscle synergies that are modifiable in a task-dependent manner be used for equilibrium control in stance.

SBA MCQs for the MRCS Part A

2012 ◽  
Author(s):  
Sri G. Thrumurthy ◽  
Tania Samantha De Silva ◽  
Zia Moinuddin ◽  
Stuart Enoch
Keyword(s):  
Clinical Case ◽  
Multiple Choice ◽  
Surgical Anatomy ◽  
Surgical Patients ◽  
Multiple Choice Questions ◽  
Basic Sciences ◽  
Self Assessment ◽  
High Level ◽  
Factual Recall ◽  
Selection Of

Specifically designed to help candidates revise for the MRCS exam, this book features 350 Single Best Answer multiple choice questions, covering the whole syllabus. Containing everything candidates need to pass the MRCS Part A SBA section of the exam, it focuses intensively on the application of basic sciences (applied surgical anatomy, physiology, and pathology) to the management of surgical patients. The high level of detail included within the questions and their explanations allows effective self-assessment of knowledge and quick identification of key areas requiring further attention. Varying approaches to Single Best Answer multiple choice questions are used, giving effective exam practice and guidance through revision and exam technique. This includes clinical case questions, 'positively-worded' questions, requiring selection of the most appropriate of relatively correct answers; 'two-step' or 'double-jump' questions, requiring several cognitive steps to arrive at the correct answer; as well as 'factual recall' questions, prompting basic recall of facts.

scholarly journals An Algorithm for Choosing the Optimal Number of Muscle Synergies during Walking

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3311
Author(s):  
Riccardo Ballarini ◽  
Marco Ghislieri ◽  
Marco Knaflitz ◽  
Valentina Agostini
Keyword(s):  
Motor Task ◽  
Optimal Number ◽  
The Other ◽  
Simulated Dataset ◽  
Muscle Synergies ◽  
Mean Square ◽  
Real Dataset ◽  
Traditional Approaches ◽  
Selection Of ◽  
Semg Signals

In motor control studies, the 90% thresholding of variance accounted for (VAF) is the classical way of selecting the number of muscle synergies expressed during a motor task. However, the adoption of an arbitrary cut-off has evident drawbacks. The aim of this work is to describe and validate an algorithm for choosing the optimal number of muscle synergies (ChoOSyn), which can overcome the limitations of VAF-based methods. The proposed algorithm is built considering the following principles: (1) muscle synergies should be highly consistent during the various motor task epochs (i.e., remaining stable in time), (2) muscle synergies should constitute a base with low intra-level similarity (i.e., to obtain information-rich synergies, avoiding redundancy). The algorithm performances were evaluated against traditional approaches (threshold-VAF at 90% and 95%, elbow-VAF and plateau-VAF), using both a simulated dataset and a real dataset of 20 subjects. The performance evaluation was carried out by analyzing muscle synergies extracted from surface electromyographic (sEMG) signals collected during walking tasks lasting 5 min. On the simulated dataset, ChoOSyn showed comparable performances compared to VAF-based methods, while, in the real dataset, it clearly outperformed the other methods, in terms of the fraction of correct classifications, mean error (ME), and root mean square error (RMSE). The proposed approach may be beneficial to standardize the selection of the number of muscle synergies between different research laboratories, independent of arbitrary thresholds.

scholarly journals Photodynamic Therapy Combined with Antibiotics or Antifungals against Microorganisms That Cause Skin and Soft Tissue Infections: A Planktonic and Biofilm Approach to Overcome Resistances

2021 ◽  
Vol 14 (7) ◽  
pp. 603
Author(s):  
Vanesa Pérez-Laguna ◽  
Isabel García-Luque ◽  
Sofía Ballesta ◽  
Antonio Rezusta ◽  
Yolanda Gilaberte
Keyword(s):  
Photodynamic Therapy ◽  
Soft Tissues ◽  
Combined Treatment ◽  
Resistance Pattern ◽  
Antimicrobial Photodynamic Therapy ◽  
Antimicrobial Drugs ◽  
Bacteria And Fungi ◽  
High Level ◽  
Selection Of

The present review covers combination approaches of antimicrobial photodynamic therapy (aPDT) plus antibiotics or antifungals to attack bacteria and fungi in vitro (both planktonic and biofilm forms) focused on those microorganisms that cause infections in skin and soft tissues. The combination can prevent failure in the fight against these microorganisms: antimicrobial drugs can increase the susceptibility of microorganisms to aPDT and prevent the possibility of regrowth of those that were not inactivated during the irradiation; meanwhile, aPDT is effective regardless of the resistance pattern of the strain and their use does not contribute to the selection of antimicrobial resistance. Additive or synergistic antimicrobial effects in vitro are evaluated and the best combinations are presented. The use of combined treatment of aPDT with antimicrobials could help overcome the difficulty of fighting high level of resistance microorganisms and, as it is a multi-target approach, it could make the selection of resistant microorganisms more difficult.

GIS Based Multi-Criteria decision support system and machine learning for Hospital Site Selection case study Oran - Algeria

2022 ◽  
Vol 14 (1) ◽  
pp. 0-0
Keyword(s):  
Site Selection ◽  
Decision Makers ◽  
Analysis Method ◽  
Automatic Learning ◽  
Hospital Site ◽  
Set Up ◽  
High Level ◽  
Selection Of ◽  
The Ideal

The selection of hospital sites is one of the most important choice a decision maker has to take so as to resist the pandemic. The decision may considerably affect the outbreak transmission in terms of efficiency , budget, etc. The main targeted objective of this study is to find the ideal location where to set up a hospital in the willaya of Oran Alg. For this reason, we have used a geographic information system coupled to the multi-criteria analysis method AHP in order to evaluate diverse criteria of physiological positioning , environmental and economical. Another objective of this study is to evaluate the advanced techniques of the automatic learning . the method of the random forest (RF) for the patterning of the hospital site selection in the willaya of Oran. The result of our study may be useful to decision makers to know the suitability of the sites as it provides a high level of confidence and consequently accelerate the power to control the COVID19 pandemic.

scholarly journals Electromyographic activity from human laryngeal, pharyngeal, and submental muscles during swallowing

1999 ◽  
Vol 86 (5) ◽  
pp. 1663-1669 ◽  
Author(s):  
A. L. Perlman ◽  
P. M. Palmer ◽  
T. M. McCulloch ◽  
D. J. Vandaele
Keyword(s):  
Muscle Activity ◽  
Total Duration ◽  
Normal Subjects ◽  
Electromyographic Activity ◽  
Surface Electrodes ◽  
Submental Muscles ◽  
Temporal Relationships ◽  
Dependent Change ◽  
Significant Difference ◽  
High Level

The durations and temporal relationships of electromyographic activity from the submental complex, superior pharyngeal constrictor, cricopharyngeus, thyroarytenoid, and interarytenoid muscles were examined during swallowing of saliva and of 5- and 10-ml water boluses. Bipolar, hooked-wire electrodes were inserted into all muscles except for the submental complex, which was studied with bipolar surface electrodes. Eight healthy, normal, subjects produced five swallows of each of three bolus volumes for a total of 120 swallows. The total duration of electromyographic activity during the pharyngeal stage of the swallow did not alter with bolus condition; however, specific muscles did show a volume-dependent change in electromyograph duration and time of firing. Submental muscle activity was longest for saliva swallows. The interarytenoid muscle showed a significant difference in duration between the saliva and 10-ml water bolus. Finally, the interval between the onset of laryngeal muscle activity (thyroarytenoid, interarytenoid) and of pharyngeal muscle firing patterns (superior pharyngeal constrictor onset, cricopharyngeus offset) decreased as bolus volume increased. The pattern of muscle activity associated with the swallow showed a high level of intrasubject agreement; the presence of somewhat different patterns among subjects indicated a degree of population variance.

scholarly journals Corrosion of carbon steel components in the French high-level waste programme: evolution of disposal concept and selection of materials

2017 ◽  
Vol 52 (sup1) ◽  
pp. 17-24 ◽  
Author(s):  
Didier Crusset ◽  
Valérie Deydier ◽  
Sophia Necib ◽  
Jean-Marie Gras ◽  
Pierre Combrade ◽  
...  
Keyword(s):  
Carbon Steel ◽  
High Level Waste ◽  
High Level ◽  
Selection Of

scholarly journals SELECTION OF SHAPE AND DIMENSIONS OF SUPPORT ELEMENT OF PAIRED ORTHOGONAL WALKING MOVER

2021 ◽  
pp. 12-16
Author(s):  
V. V. Arykantsev ◽  
V. V. Chernyshev ◽  
N. G. Sharonov
Keyword(s):  
Bearing Capacity ◽  
Contact Area ◽  
Optimal Size ◽  
Supporting Surface ◽  
Walking Machine ◽  
Size And Shape ◽  
Support Element ◽  
Supporting Element ◽  
Selection Of

The paper describes the principle of choosing the optimal size and shape of the supporting element of a walking machine, provided that the maximum possible contact area with the supporting surface is provided for moving on snow or soils with a low bearing capacity. The study was carried out for an orthogonal walking propulsion device, but it can also be used for walking mechanisms of other types.

scholarly journals FEATURES OF ADVENTURE TOURISM AND PROSPECTS FOR ITS DEVELOPMENT IN RUSSIA

2017 ◽  
Vol 11 (3) ◽  
pp. 51-58
Author(s):  
Татьяна Никонова ◽  
Tatyana Nikonova ◽  
Валерия ГУСАРОВА ◽  
Valeriya GUSAROVA ◽  
Ольга Пережогина ◽  
...  
Keyword(s):  
Healthy Lifestyle ◽  
Transport Infrastructure ◽  
Extreme Sports ◽  
Professional Background ◽  
Adventure Tourism ◽  
Tourist Infrastructure ◽  
High Level ◽  
Negative Factors ◽  
Selection Of

In the last few years, the development of adventure tourism as a kind of active tourism initiatives, tourism firms have become more visible. Adventuretourism (adventure tourism) is different in originality and unusual variety of tours. It includes exotic travel, extreme sports, a specific move connected with risk and danger to life. In this regard, the article highlights the criterion of the differences of adventure tourism from other types of active travel. The authors point out the the main reasons for the popularity of adventure tourism of the article, among which are following: healthy lifestyle popularization, prestige of the activity of the pleasure, the desire of the modern tourist for new experiences and the rush of emotion, the possibility of self-realization, improving credibility and promotion in society through adventure tourism, including with help of social networks. Taking into account the growing popularity of adventure tourism in the world, the authors of the article analyzes the factors of Russia’s competitiveness for the adventure tourism development. It is revealed that strengths are rail transport infrastructure and a high level of health and hygiene. The article admits that now the development of adventure tourism in Russia is constrained by a number of negative factors to be overcome. Among them are the lack of a comprehensive look at the geography of Russia from the standpoint of the selection of adventure territories, the unsatisfactory level of tourist infrastructure of adventure, poor range and low quality of ser- vices adventure tourism, weak professional background of the staff.

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