scholarly journals Effect of Task Failure on Intermuscular Coherence Measures in Synergistic Muscles

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Anna Margherita Castronovo ◽  
Cristiano De Marchis ◽  
Maurizio Schmid ◽  
Silvia Conforto ◽  
Giacomo Severini
Keyword(s):  
Muscle Synergy ◽  
Motor Tasks ◽  
Task Failure ◽  
Leg Extension ◽  
The Face ◽  
Intermuscular Coherence ◽  
Synergistic Muscles

The term “task failure” describes the point when a person is not able to maintain the level of force required by a task. As task failure approaches, the corticospinal command to the muscles increases to maintain the required level of force in the face of a decreased mechanical efficacy. Nevertheless, most motor tasks require the synergistic recruitment of several muscles. How this recruitment is affected by approaching task failure is still not clear. The increase in the corticospinal drive could be due to an increase in synergistic recruitment or to overlapping commands sent to the muscles individually. Herein, we investigated these possibilities by combining intermuscular coherence and synergy analysis on signals recorded from three muscles of the quadriceps during dynamic leg extension tasks. We employed muscle synergy analysis to investigate changes in the coactivation of the muscles. Three different measures of coherence were used. Pooled coherence was used to estimate the command synchronous to all three muscles, pairwise coherence the command shared across muscle pairs and residual coherence the command peculiar to each couple of muscles. Our analysis highlights an overall decrease in synergistic command at task failure and an intensification of the contribution of the nonsynergistic shared command.

Intermuscular coherence contributions in synergistic muscles during pedaling

2015 ◽  
Vol 233 (6) ◽  
pp. 1907-1919 ◽  
Author(s):  
Cristiano De Marchis ◽  
Giacomo Severini ◽  
Anna Margherita Castronovo ◽  
Maurizio Schmid ◽  
Silvia Conforto
Keyword(s):  
Intermuscular Coherence ◽  
Synergistic Muscles

Men Exhibit Greater Pain Pressure Thresholds and Times to Task Failure but Not Performance Fatigability Following Self-Paced Exercise

2021 ◽  
pp. 003151252110350
Author(s):  
Karina Noboa ◽  
Joshua Keller ◽  
Kipp Hergenrader ◽  
Terry Housh ◽  
John Paul Anders ◽  
...  
Keyword(s):  
Sex Differences ◽  
Perceived Exertion ◽  
Rating Of Perceived Exertion ◽  
Muscle Size ◽  
Maximal Voluntary Isometric Contraction ◽  
Cross Sectional ◽  
Task Failure ◽  
Leg Extension ◽  
Pressure Threshold ◽  
Pain Pressure Threshold

The purpose of the current study was to determine if, and to what extent, sex differences in performance fatigability after a sustained, bilateral leg extension, anchored to a moderate rating of perceived exertion (RPE), could be attributed to muscle size, muscular strength, or pain pressure threshold (PPT) in young, healthy adults. Thirty adults (men: n = 15, women: n = 15) volunteered to complete a sustained leg extension task anchored to RPE = 5 (10-point OMNI scale) as well as pretest and posttest maximal voluntary isometric contraction (MVIC) trials. The fatigue-induced decline in MVIC force was defined as performance fatigability. We used muscle cross-sectional area (mCSA) to quantify muscle size and a dolorimeter to assess PPT. The sustained task induced fatigue such that both men and women exhibited significant ( p < 0.05) decreases in MVIC force from pretest to posttest ( M = 113.3, SD =24.2 kg vs. M = 98.3, SD = 23.1 kg and M = 73.1, SD =14.5 kg vs. M = 64.1, SD = 16.2 kg, respectively), with no significant sex differences in performance fatigability (grand M = 12.6, SD =10.6%). Men, however, exhibited significantly ( p < 0.05) longer time to task failure (TTF) than women ( M = 166.1, SD =83.0 seconds vs. M = 94.6, SD =41.7) as well as greater PPT ( M = 5.9, SD = 2.2 kg vs. M = 3.4, SD =1.1 kg). The only significant predictor of performance fatigability was PPT. In conclusion, differences in PPT, at least in part, mediate variations in TTF during self-paced exercise anchored to a specific RPE and resulting in performance fatigability.

scholarly journals TRAINING AND IMPROVING BILLIARD TECHNIQUE IN STUDENTS WITH RESPECT TO THE SEQUENCE OF SOLUTIONS TO MOTOR TASKS IN THE NERVOUS SYSTEM

2020 ◽  
Vol 20 (3) ◽  
pp. 79-87
Author(s):  
R Gimazov ◽  
S Jenanyan
Keyword(s):  
Nervous System ◽  
Experimental Method ◽  
Objective Assessment ◽  
Muscle Synergy ◽  
Control Group ◽  
Vertical Position ◽  
Muscle Coordination ◽  
Competitive Performance ◽  
Motor Tasks ◽  
Experimental Group

Aim. The paper aims to compare the effectiveness of training of billiard players, who follow the program of sports school, and those, who participate in the experiment for improving billiard technique based on the sequence of solutions to motor tasks in the nervous system. Materials and methods. The experiment involved control and experimental groups of young males and females of 8 people each with sports skills from 1st junior category to a candidate for master of sport in billiards. For an objective assessment of billiard skills acquisition a force platform was used to study muscle coordination and neural regulation of vertical position (patent № 2547991 and № 2547992, Russia). Results. At the beginning of the experiment, two groups were equal in competitive performance (Z = 0.866, р = 0.3865). The experimental method allowed athletes to increase a growth rate of kinesthetic sensitivity by 33.5 % (from 0.242 ± 0.08 units to 0.161 ± ± 0.07 units (хaverage ± σ)), muscle synergy – by 56.1 % (from 95.9 ± 31.1 units to 117.6 ± 27.7 units (хaverage ± σ)). In the control group, a deterioration of kinesthetic sensitivity by 6.3 % was recorded (from 0.347 ± 0.12 units to 0.369 ± 0.12 units (хaverage ± σ)), as well as a decrease in muscle synergy by 15.8 % (from 66.4 ± 30.8 units to 55.9 ± 20.1 units (хaverage ± σ)). The analysis of billiard performance is confirmed statistically (Z = –2.252, p = 0.02436) in favor of the experimental group. Conclusion. The results of the study statistically prove the effectiveness of the experimental method of improving billiard technique based on the sequence of solutions to motor tasks in the nervous system. The coach's support of natural biological sequence when solving motor tasks in the nervous system allowed the experimental group to double its competitive performance compared to the control group.

Why do people believe in a zero-sum economy?

2018 ◽  
Vol 41 ◽  
Author(s):  
Samuel G. B. Johnson
Keyword(s):  
Perspective Taking ◽  
Evolutionary Model ◽  
Everyday Experience ◽  
Coalitional Psychology ◽  
The Face ◽  
Zero Sum

AbstractZero-sum thinking and aversion to trade pervade our society, yet fly in the face of everyday experience and the consensus of economists. Boyer & Petersen's (B&P's) evolutionary model invokes coalitional psychology to explain these puzzling intuitions. I raise several empirical challenges to this explanation, proposing two alternative mechanisms – intuitive mercantilism (assigning value to money rather than goods) and errors in perspective-taking.

Mars: was There an Ancient Eden?

1997 ◽  
Vol 161 ◽  
pp. 203-218 ◽  
Author(s):  
Tobias C. Owen
Keyword(s):  
Positive Answer ◽  
Biogenic Elements ◽  
Habitable Zones ◽  
The Face ◽  
The Origin Of Life ◽  
Early Mars ◽  
Favorable Conditions ◽  
Open Question ◽  
Rocky Planets ◽  
Impact Erosion

AbstractThe clear evidence of water erosion on the surface of Mars suggests an early climate much more clement than the present one. Using a model for the origin of inner planet atmospheres by icy planetesimal impact, it is possible to reconstruct the original volatile inventory on Mars, starting from the thin atmosphere we observe today. Evidence for cometary impact can be found in the present abundances and isotope ratios of gases in the atmosphere and in SNC meteorites. If we invoke impact erosion to account for the present excess of129Xe, we predict an early inventory equivalent to at least 7.5 bars of CO2. This reservoir of volatiles is adequate to produce a substantial greenhouse effect, provided there is some small addition of SO2(volcanoes) or reduced gases (cometary impact). Thus it seems likely that conditions on early Mars were suitable for the origin of life – biogenic elements and liquid water were present at favorable conditions of pressure and temperature. Whether life began on Mars remains an open question, receiving hints of a positive answer from recent work on one of the Martian meteorites. The implications for habitable zones around other stars include the need to have rocky planets with sufficient mass to preserve atmospheres in the face of intensive early bombardment.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

The glycomes of Caenorhabditis elegans and other model organisms

2002 ◽  
Vol 69 ◽  
pp. 117-134 ◽  
Author(s):  
Stuart M. Haslam ◽  
David Gems ◽  
Howard R. Morris ◽  
Anne Dell
Keyword(s):  
Caenorhabditis Elegans ◽  
Current Knowledge ◽  
Structural Data ◽  
Model Organisms ◽  
Entire Genome ◽  
C Elegans ◽  
The Face ◽  
Area Of Concern ◽  
Nematode Worm

There is no doubt that the immense amount of information that is being generated by the initial sequencing and secondary interrogation of various genomes will change the face of glycobiological research. However, a major area of concern is that detailed structural knowledge of the ultimate products of genes that are identified as being involved in glycoconjugate biosynthesis is still limited. This is illustrated clearly by the nematode worm Caenorhabditis elegans, which was the first multicellular organism to have its entire genome sequenced. To date, only limited structural data on the glycosylated molecules of this organism have been reported. Our laboratory is addressing this problem by performing detailed MS structural characterization of the N-linked glycans of C. elegans; high-mannose structures dominate, with only minor amounts of complex-type structures. Novel, highly fucosylated truncated structures are also present which are difucosylated on the proximal N-acetylglucosamine of the chitobiose core as well as containing unusual Fucα1–2Gal1–2Man as peripheral structures. The implications of these results in terms of the identification of ligands for genomically predicted lectins and potential glycosyltransferases are discussed in this chapter. Current knowledge on the glycomes of other model organisms such as Dictyostelium discoideum, Saccharomyces cerevisiae and Drosophila melanogaster is also discussed briefly.

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