scholarly journals Stroke impairs the control of isometric forces and muscle activations in the ipsilesional arm

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Laura Pellegrino ◽  
Martina Coscia ◽  
Psiche Giannoni ◽  
Lucio Marinelli ◽  
Maura Casadio
Keyword(s):  
Daily Living ◽  
Isometric Force ◽  
Muscle Synergies ◽  
Behavioral Performance ◽  
Joint Torques ◽  
Efficient Control ◽  
Muscle Activations ◽  
A Minor ◽  
Isometric Forces ◽  
Minor Extent

AbstractStroke often impairs the control of the contralesional arm, thus most survivors rely on the ipsilesional arm to perform daily living activities that require an efficient control of movements and forces. Whereas the ipsilesional arm is often called ‘unaffected’ or ‘unimpaired’, several studies suggested that during dynamic tasks its kinematics and joint torques are altered. Is stroke also affecting the ability of the ipsilesional arm to produce isometric force, as when pushing or pulling a handle? Here, we address this question by analyzing behavioral performance and muscles’ activity when subjects applied an isometric force of 10 N in eight coplanar directions. We found that stroke affected the ability to apply well-controlled isometric forces with the ipsilesional arm, although to a minor extent compared to the contralesional arm. The spinal maps, the analysis of single muscle activities and the organization of muscle synergies highlighted that this effect was mainly associated with abnormal activity of proximal muscles with respect to matched controls, especially when pushing or pulling in lateral directions.

scholarly journals Robustness of muscle synergies underlying three-dimensional force generation at the hand in healthy humans

2012 ◽  
Vol 107 (8) ◽  
pp. 2123-2142 ◽  
Author(s):  
Jinsook Roh ◽  
William Z. Rymer ◽  
Randall F. Beer
Keyword(s):  
Nervous System ◽  
Matrix Factorization ◽  
Isometric Force ◽  
Three Dimensional ◽  
Movement Control ◽  
Force Generation ◽  
Muscle Synergy ◽  
Muscle Synergies ◽  
Healthy Humans ◽  
Isometric Forces

Previous studies using advanced matrix factorization techniques have shown that the coordination of human voluntary limb movements may be accomplished using combinations of a small number of intermuscular coordination patterns, or muscle synergies. However, the potential use of muscle synergies for isometric force generation has been evaluated mostly using correlational methods. The results of such studies suggest that fixed relationships between the activations of pairs of muscles are relatively rare. There is also emerging evidence that the nervous system uses independent strategies to control movement and force generation, which suggests that one cannot conclude a priori that isometric force generation is accomplished by combining muscle synergies, as shown in movement control. In this study, we used non-negative matrix factorization to evaluate the ability of a few muscle synergies to reconstruct the activation patterns of human arm muscles underlying the generation of three-dimensional (3-D) isometric forces at the hand. Surface electromyographic (EMG) data were recorded from eight key elbow and shoulder muscles during 3-D force target-matching protocols performed across a range of load levels and hand positions. Four synergies were sufficient to explain, on average, 95% of the variance in EMG datasets. Furthermore, we found that muscle synergy composition was conserved across biomechanical task conditions, experimental protocols, and subjects. Our findings are consistent with the view that the nervous system can generate isometric forces by assembling a combination of a small number of muscle synergies, differentially weighted according to task constraints.

Methodology to Customize Maximal Isometric Forces for Hill-Type Muscle Models

2017 ◽  
Vol 33 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Fabien Dal Maso ◽  
Mickaël Begon ◽  
Maxime Raison
Keyword(s):  
Muscle Force ◽  
Biceps Brachii ◽  
Isometric Force ◽  
Force Estimation ◽  
Triceps Brachii ◽  
Joint Torques ◽  
Musculoskeletal Models ◽  
Flexion Extension ◽  
Isometric Forces ◽  
Maximal Isometric Force

One approach to increasing the confidence of muscle force estimation via musculoskeletal models is to minimize the root mean square error (RMSE) between joint torques estimated from electromyographic-driven musculoskeletal models and those computed using inverse dynamics. We propose a method that reduces RMSE by selecting subsets of combinations of maximal voluntary isometric contraction (MVIC) trials that minimize RMSE. Twelve participants performed 3 elbow MVIC in flexion and in extension. An upper-limb electromyographic-driven musculoskeletal model was created to optimize maximum muscle stress and estimate the maximal isometric force of the biceps brachii, brachialis, brachioradialis, and triceps brachii. Maximal isometric forces were computed from all possible combinations of flexion-extension trials. The combinations producing the smallest RMSE significantly reduced the normalized RMSE to 7.4% compared with the combination containing all trials (9.0%). Maximal isometric forces ranged between 114–806 N, 64–409 N, 236–1511 N, and 556–3434 N for the brachii, brachialis, brachioradialis, and triceps brachii, respectively. These large variations suggest that customization is required to reduce the difference between models and actual participants’ maximal isometric force. While the smallest previously reported RMSE was 10.3%, the proposed method reduced the RMSE to 7.4%, which may increase the confidence of muscle force estimation.

scholarly journals Upper-Limb Isometric Force Feasible Set: Evaluation of Joint Torque-Based Models

Biomechanics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 102-117
Author(s):  
Nasser Rezzoug ◽  
Vincent Hernandez ◽  
Philippe Gorce
Keyword(s):  
Upper Limb ◽  
Isometric Force ◽  
Joint Torque ◽  
Force Distribution ◽  
Prediction Errors ◽  
Feasible Set ◽  
Joint Torques ◽  
Motor Abilities ◽  
Capacity Evaluation ◽  
Measured Force

A force capacity evaluation for a given posture may provide better understanding of human motor abilities for applications in sport sciences, rehabilitation and ergonomics. From data on posture and maximum isometric joint torques, the upper-limb force feasible set of the hand was predicted by four models called force ellipsoid, scaled force ellipsoid, force polytope and scaled force polytope, which were compared with a measured force polytope. The volume, shape and force prediction errors were assessed. The scaled ellipsoid underestimated the maximal mean force, and the scaled polytope overestimated it. The scaled force ellipsoid underestimated the volume of the measured force distribution, whereas that of the scaled polytope was not significantly different from the measured distribution but exhibited larger variability. All the models characterized well the elongated shape of the measured force distribution. The angles between the main axes of the modelled ellipsoids and polytopes and that of the measured polytope were compared. The values ranged from 7.3° to 14.3°. Over the entire surface of the force ellipsoid, 39.7% of the points had prediction errors less than 50 N; 33.6% had errors between 50 and 100 N; and 26.8% had errors greater than 100N. For the force polytope, the percentages were 56.2%, 28.3% and 15.4%, respectively.

Factors affecting the future of the Scottish hydrometric network

1987 ◽  
Vol 78 (4) ◽  
pp. 269-274 ◽  
Author(s):  
T. Poodle
Keyword(s):  
Data Acquisition ◽  
Computer Systems ◽  
Economic Recession ◽  
Data Standards ◽  
Factors Affecting ◽  
Economic Climate ◽  
A Minor ◽  
The Cost ◽  
Minor Extent

ABSTRACTThe Scottish Hydrometric Network consists of a number of river gauging stations which have been located at sites considered suitable to provide long term flow records. Economic recession has placed some stress on the gauging programme, and has given rise to extensive closures of gauging stations in England and, to a minor extent so far, in Scotland. The way in which the network became established provides a mixture of strengths and weaknesses which could have unpredictable consequences in an adverse economic climate. Changing technology provides some opportunity to reduce the cost of data acquisition and improve the deployment of manpower, while maintaining data standards. In these changing circumstances, particularly with extensive use of computer systems, it is important that standards are established for data returned to the Water Archive and that the network is not allowed to degenerate by default.

Postactivation Potentiation of Force Is Independent of H-Reflex Excitability

2008 ◽  
Vol 3 (2) ◽  
pp. 219-231 ◽  
Author(s):  
Matthew J. Hodgson ◽  
David Docherty ◽  
E. Paul Zehr
Keyword(s):  
Isometric Force ◽  
Plantar Flexion ◽  
Force Production ◽  
H Reflex ◽  
Postactivation Potentiation ◽  
Neural Excitability ◽  
Reflex Excitability ◽  
Before And After ◽  
History Of ◽  
A Minor

The contractile history of muscle can potentiate electrically evoked force production. A link to voluntary force production, related in part to an increase in reflex excitability, has been suggested.Purpose:Our purpose was to quantify the effect of postactivation potentiation on voluntary force production and spinal H-reflex excitability during explosive plantar fexion actions.Methods:Plantar flexor twitch torque, soleus H-reflex amplitudes, and the rate of force development of explosive plantar fexion were measured before and after 4 separate conditioning trials (3 × 5 s maximal contractions).Results:Twitch torque and rate of force production during voluntary explosive plantar flexion were significantly increased (P < .05) while H-reflex amplitudes remained unchanged. Although twitch torque was significantly higher after conditioning, leading to a small increase in the rate of voluntary force production, this was unrelated to changes in reflex excitability.Conclusion:We conclude that postactivation potentiation may result in a minor increase in the rate of voluntary isometric force production that is unrelated to neural excitability.

Cupressus arizonica (Arizona cypress).

2021 ◽  
Author(s):  
Sylvan Kaufman
Keyword(s):  
New World ◽  
Erosion Control ◽  
Economic Importance ◽  
Christmas Trees ◽  
Cupressus Arizonica ◽  
A Minor ◽  
Minor Extent

Abstract At present, in the New World, C. arizonica and its varieties are of low economic importance, but they are sometimes cut for fenceposts, fuelwood and lumber, and recently they have become popular as Christmas trees. By contrast, the Arizona cypress (C. arizonica var. arizonica) and the smooth cypress (C. arizonica var. glabra) are widespread in Europe and are used for landscaping, erosion control, windbreaks, and to a minor extent for lumber.

Chapter II. The World Economy

1983 ◽  
Vol 106 ◽  
pp. 26-38
Keyword(s):  
North America ◽  
Industrial Production ◽  
World Economy ◽  
Western Europe ◽  
West Germany ◽  
The Us ◽  
The World ◽  
The Uk ◽  
A Minor ◽  
Minor Extent

The recovery in the OECD area gathered pace in the second quarter, when its total GDP probably increased by as much as 1 per cent. The rise was, however, heavily concentrated in North America and particularly the US. There may well have been a slight fall in Western Europe, where the level of industrial production hardly changed and increases in gross product in West Germany and, to a minor extent, in France were outweighed by falls in Italy and (according to the expenditure measure) the UK.

scholarly journals Tracing the (hidden) spatialities of digital agendas: the case of ‘Digital Hungary’

2019 ◽  
Vol 26 (2) ◽  
pp. 135-150
Author(s):  
Krisztina Varró
Keyword(s):  
Analytical Framework ◽  
Spatial Dimension ◽  
Spatial Development ◽  
Digital Transformation ◽  
A Minor ◽  
Development Trajectories ◽  
Minor Extent

Policies that aim at bringing about a digital transformation (seek to) create the conditions for particular spatial development trajectories. Yet, the understandings, explicit and implicit, of space advanced by digital agendas have remained rather underexposed to date. This paper addresses this gap by developing a Foucauldian-inspired discourse-analytical framework and applies it to the programme of ‘Digital Hungary’. It is argued that policies of digitalisation in Hungary only to a minor extent consider the spatial dimension, and their impact potentially undermines the declared aims of spatial development at different scales.

scholarly journals Bryophytes of the upper reaches of the Western Bug River (Lviv Region, Ukraine)

2020 ◽  
pp. 7-24
Author(s):  
Yura Drach ◽  
Zvenysvala Mamchur
Keyword(s):  
Development Strategy ◽  
Life Forms ◽  
Wetland Ecosystems ◽  
Substrate Preferences ◽  
Ecological Features ◽  
The Development Strategy ◽  
Cold Tolerant ◽  
A Minor ◽  
First Time ◽  
Minor Extent

In the article, the bryophytes of the upper reaches of the Western Bug River, which is physically and geographically located within Male Polissya, partly Roztochia, and to a minor extent in the Gologoro-Voronyatsky denudo-structural hills, have been studied. Based on our survey, a list of the bryophytes has been compiled for the first time. Ecological features, substrate preferences and life forms of the bryophytes have been analysed. According to the ecological features, subheliophytes (30.9%) and hemisciophytes (30.9%) predominate in the spectrum of heliomorphs; mesophytes (29.7%), hygromesophytes (21.2%) and xeromesophytes – in the spectrum of hydromorphs (19.4%); cold-tolerant species (59.4%) – in the spectrum of thermomorphs. Based on the analysis of the substrate preferences of the bryophytes, the following groups were identified: epigeans (116 species), epixils (56 species), epiphytes (46 species), epiliths (43 species), aquatic (22 species). The prevailing life forms are turf (30.3%), rough mat (18.2%), weft (15.2%), tuft (10.3%) and smooth mat (9.7%). 3 species that are officially recognised as rare and 16 species that are recognized as regionally rare have been found. In the group of bryophytes associated with wetland ecosystems, 2 officially rare and 6 regionally rare species were found in the study area. Given the large areas of drained land in Lviv Region, these species are of particular value, especially in the context of conservation of the biodiversity and protection of the valuable natural areas in accordance with the Development Strategy of Lviv Region by 2027.

scholarly journals Lower complexity of motor primitives ensures robust control of high-speed human locomotion

2020 ◽  
Author(s):  
Alessandro Santuz ◽  
Antonis Ekizos ◽  
Yoko Kunimasa ◽  
Kota Kijima ◽  
Masaki Ishikawa ◽  
...  
Keyword(s):  
High Speed ◽  
Muscle Activation ◽  
Human Locomotion ◽  
Muscle Synergies ◽  
Activation Patterns ◽  
Motor Primitives ◽  
Muscle Activation Patterns ◽  
Relative Contribution ◽  
Muscle Activations ◽  
Low Dimensional

AbstractWalking and running are mechanically and energetically different locomotion modes. For selecting one or another, speed is a parameter of paramount importance. Yet, both are likely controlled by similar low-dimensional neuronal networks that reflect in patterned muscle activations called muscle synergies. Here, we investigated how humans synergistically activate muscles during locomotion at different submaximal and maximal speeds. We analysed the duration and complexity (or irregularity) over time of motor primitives, the temporal components of muscle synergies. We found that the challenge imposed by controlling high-speed locomotion forces the central nervous system to produce muscle activation patterns that are wider and less complex relative to the duration of the gait cycle. The motor modules, or time-independent coefficients, were redistributed as locomotion speed changed. These outcomes show that robust locomotion control at challenging speeds is achieved by modulating the relative contribution of muscle activations and producing less complex and wider control signals, whereas slow speeds allow for more irregular control.

Sign in / Sign up

Export Citation Format

Share Document