Average force obtained from the impulse or from the mechanical work?

2021 ◽  
Vol 56 (5) ◽  
pp. 053006
Author(s):  
F Ribas ◽  
J A Espinosa ◽  
F Lusquiños
Keyword(s):  
Mechanical Work ◽  
Average Force

scholarly journals The high energetic cost of rapid force development in cyclic muscle contraction

2020 ◽  
Author(s):  
Tim J. van der Zee ◽  
Arthur D. Kuo
Keyword(s):  
Metabolic Rate ◽  
Muscle Contraction ◽  
Muscle Force ◽  
Force Production ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Average Force ◽  
Force Development ◽  
The Cost

AbstractMuscles consume metabolic energy for active movement, particularly when performing mechanical work or producing force. Less appreciated is the cost for activating and deactivating muscle quickly, which adds considerably to the overall cost of cyclic force production (Chasiotis et al., 1987). But the cost relative to mechanical work, which features in many movements, is unknown. We therefore tested whether fast activation-deactivation is costly compared to performing work or producing isometric force. We hypothesized that metabolic cost would increase with a proposed measure termed force-rate (rate of increase in muscle force) in cyclic tasks, separate from mechanical work or average force level. We tested humans (N = 9) producing cyclic knee extension torque against an isometric dynamometer (torque 22 N-m, cyclic waveform frequencies 0.5 – 2.5 Hz), while also quantifying the force and work of muscle fascicles against series elasticity (with ultrasonography), along with metabolic rate through respirometry. Net metabolic rate increased by more than fourfold (10.5 to 46.7 W) with waveform frequency. At high frequencies, the hypothesized force-rate cost accounted for nearly half (41%) of energy expenditure. This exceeded the cost for average force (17%) and was comparable to the cost for shortening work (42%). The energetic cost is explained by a simple first-order model of rate-limiting steps in muscle contraction, primarily crossbridge dynamics. The force-rate cost could contribute substantially to the overall cost of movements that require cyclic muscle activation, such as locomotion.Summary statementThe energetic cost of isometric muscle force production during cyclic muscle contraction increases sharply with cycle frequency and in proportion to the rate of force development

scholarly journals The high energetic cost of rapid force development in muscle

2021 ◽  
pp. jeb.233965
Author(s):  
Tim J. van der Zee ◽  
Arthur D. Kuo
Keyword(s):  
Metabolic Rate ◽  
Muscle Activation ◽  
Muscle Force ◽  
Force Production ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Average Force ◽  
Rate Of Increase ◽  
The Cost

Muscles consume metabolic energy for active movement, particularly when performing mechanical work or producing force. Less appreciated is the cost for activating muscle quickly, which adds considerably to the overall cost of cyclic force production (Chasiotis et al., 1987). But the cost magnitude relative to mechanical work, which features in many movements, is unknown. We therefore tested whether fast activation is costly compared to performing work or producing isometric force. We hypothesized that metabolic cost would increase with a proposed measure termed force-rate (rate of increase in muscle force) in cyclic tasks, separate from mechanical work or average force level. We tested humans (N=9) producing cyclic knee extension torque against an isometric dynamometer (torque 22 N-m, cyclic waveform frequencies 0.5 – 2.5 Hz), while also quantifying quadriceps muscle force and work against series elasticity (with ultrasonography), along with metabolic rate through respirometry. Net metabolic rate increased by more than fourfold (10.5 to 46.7 W) with waveform frequency. At high frequencies, the hypothesized force-rate cost accounted for nearly half (40%) of energy expenditure. This exceeded the cost for average force (17%) and was comparable to the cost for shortening work (43%). The force-rate cost is explained by additional active calcium transport necessary for producing forces at increasing waveform frequencies, due to rate-limiting dynamics of force production. The force-rate cost could contribute substantially to the overall cost of movements that require cyclic muscle activation, such as locomotion.

COMPARATIVE ANALYSIS OF THE PHYSICAL PERFORMANCE VARIABILITY IN ATHLETES OF DIFFERENT BIORHYTHMOTYPES

2020 ◽  
pp. 5-10
Keyword(s):  
Comparative Analysis ◽  
Physical Performance ◽  
Mechanical Work ◽  
Performance Variability ◽  
Metabolic Systems ◽  
Account Planning

The variability of physical performance in representatives of various biorhythmotypes at different times of the day was studied. It has been revealed that the efficiency of metabolic systems during hours of functional optimum makes it possible to carry out large (by volume and power) physical loads, which indicates greater efficiency of mechanical work in the corresponding period. Taking these circumstances into account, planning of training loads avoids the effect of overtraining and leads to an increase in the overall level of physical performance

scholarly journals Levosimendan, milrinone and dobutamine in acute experimental pulmonary embolism

2021 ◽  
Vol 10 (Supplement_1) ◽  
Author(s):  
MD Lyhne ◽  
SJ Dragsbaek ◽  
JV Hansen ◽  
JG Schultz ◽  
A Andersen ◽  
...  
Keyword(s):  
Pulmonary Embolism ◽  
Acute Pulmonary Embolism ◽  
Cardiovascular Effects ◽  
Right Heart Catheterization ◽  
Mechanical Work ◽  
Heart Catheterization ◽  
Funding Sources ◽  
Mean Pulmonary Arterial Pressure ◽  
Acute Pe ◽  
Rv Function

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Laerdal Foundation for Acute Medicine, Novo Nordisk Foundation Background/Introduction: Acute pulmonary embolism (PE) is a frequent condition in acute cardiac care and is potentially fatal. Cause of death is right ventricular (RV) failure due to increased RV afterload from both pulmonary vascular obstruction and vasoconstriction. Inodilators are interesting drugs of choice as they may improve RV function and lower its afterload. Purpose We aimed to investigate the cardiovascular effects of three clinically relevant inodilators: levosimendan, milrinone and dobutamine in acute PE. Methods We conducted a randomized, blinded, animal study using 18 female pigs. Animals received large autologous PE until doubling of baseline mean pulmonary arterial pressure and were randomized to four logarithmically increasing doses of each inodilator. Effects were evaluated with bi-ventricular pressure-volume loop recordings, right heart catheterization and blood gas analyses. Results Induction of PE increased RV afterload and pulmonary pressure (p < 0.05) causing RV dysfunction. Levosimendan and milrinone showed beneficial hemodynamic profiles by lowering RV pressures and volume (p < 0.001) and improved RV function and cardiac output (p < 0.05) without increasing RV mechanical work. Dobutamine increased RV pressure and function (p < 0.01) but at a cost of increased mechanical work at the highest doses, showing an adverse hemodynamic profile. See Figure. Conclusion(s): In a porcine model of acute PE, levosimendan and milrinone reduced RV afterload and improved RV function, whereas dobutamine at higher doses increased RV afterload and RV mechanical work. The study motivates clinical testing of inodilators in patients with acute PE and RV dysfunction. Abstract Figure. Inodilators in acute pulmonary embolism

Stability and performance of the EnSite Precision cardiac mapping system for electrophysiology mapping and ablation procedures: results from the EnSite Precision observational study

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
D Lin ◽  
B Glover ◽  
J Colley ◽  
B Thibault ◽  
C.M Steinberg ◽  
...  
Keyword(s):  
Observational Study ◽  
Real World ◽  
Cardiac Electrophysiology ◽  
Median Number ◽  
System Stability ◽  
Cardiac Mapping ◽  
Average Force ◽  
Mapping System ◽  
Respiratory Change ◽  
Electrophysiology Mapping

Abstract Background The EnSite Precision™ Cardiac Mapping System is a catheter navigation and mapping system capable of displaying the three-dimensional (3D) position of conventional and sensor enabled electrophysiology catheters, as well as displaying cardiac electrical activity as waveform traces and dynamic 3-D maps of cardiac chambers. Objective The EnSite Precision™ Observational Study was designed to quantify and characterize the use of the EnSite Precision™ Cardiac Mapping System for mapping and ablation of cardiac arrhythmias in a real-world environment and to evaluate procedural and subsequent clinical outcomes. Methods 1065 patients were enrolled at 38 centers in the U.S. and Canada between 2017–2018. Eligible subjects were adults undergoing a cardiac electrophysiology mapping and radiofrequency ablation procedures using the EnSite Precision™ System. Results Of 989 patients who completed the protocol, a geometry was created in 936 (94.7%). Most initial maps were created using Automap (n=545, 67.0%) or a combination of Automap and manually mapping (n=151, 18.6%). Median time to create an initial map was 9.0 min (IQR 5.0–15.0), with a median number of used mapping points per minute of 92.7 (IQR 30.0–192.0). During ablation, AutoMark was used in 817 (82.6%) of procedures. The most frequent metrics for lesion color were Impedance Drop or Impedance Drop Percent (45.5% combined), time (23.9%) and average force (14.2%). At Canadian sites where LSI was an option, it was used as the color metric in 87 (45.8%) of cases (10.6% overall). The EnSite System was stable throughout 79.7% (n=788 of 989) of procedures. Factors affecting stability were respiratory change (n=88 of 989, 8.9%), patient movement (n=73, 7.4%), CS Positional Reference dislodgement (n=32, 3.2%), and cardioversion (n=19, 1.9%). Conscious sedation was used in 189 (19.1%) of patients. Acute success was reached based on the pre-defined endpoints for the procedure in 97.4% (n=963) of cases. Conclusion In a real-world study analysis, the EnSite Precision™ mapping system was associated with a high prevalence of acute procedural success, low mapping times, and high system stability. Funding Acknowledgement Type of funding source: None

scholarly journals Remodeler Catalyzed Nucleosome Repositioning: Influence of Structure and Stability

2020 ◽  
Vol 22 (1) ◽  
pp. 76
Author(s):  
Aaron Morgan ◽  
Sarah LeGresley ◽  
Christopher Fischer
Keyword(s):  
Free Energy ◽  
Dna Replication ◽  
Recent Work ◽  
Chromatin Remodeling ◽  
Chromatin Structure ◽  
Genetic Information ◽  
Molecular Machines ◽  
Mechanical Work ◽  
Eukaryotic Genome ◽  
Hydrolysis Of

The packaging of the eukaryotic genome into chromatin regulates the storage of genetic information, including the access of the cell’s DNA metabolism machinery. Indeed, since the processes of DNA replication, translation, and repair require access to the underlying DNA, several mechanisms, both active and passive, have evolved by which chromatin structure can be regulated and modified. One mechanism relies upon the function of chromatin remodeling enzymes which couple the free energy obtained from the binding and hydrolysis of ATP to the mechanical work of repositioning and rearranging nucleosomes. Here, we review recent work on the nucleosome mobilization activity of this essential family of molecular machines.

scholarly journals Twinning Behavior in Cold-Rolling Ultra-Thin Grain-Oriented Silicon Steel

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 187
Author(s):  
Bo Zhang ◽  
Li Meng ◽  
Guang Ma ◽  
Ning Zhang ◽  
Guobao Li ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Rolling Process ◽  
Silicon Steel ◽  
Mechanical Work ◽  
Area Fraction ◽  
Raw Material ◽  
Rolling Reduction ◽  
Cold Rolling Reduction ◽  
Schmid Factor ◽  
Twinning System

Twinning behaviors in grains during cold rolling have been systematically studied in preparing ultra-thin grain-oriented silicon steel (UTGO) using a commercial glassless grain-oriented silicon steel as raw material. It is found that the twinning system with the maximum Schmid factor and shear mechanical work would be activated. The area fraction of twins increased with the cold rolling reduction. The orientations of twins mainly appeared to be α-fiber (<110>//RD), most of which were {001}<110> orientation. Analysis via combining deformation orientation simulation and twinning orientation calculation suggested that {001}<110> oriented twinning occurred at 40–50% rolling reduction. The simulation also confirmed more {100} <011> oriented twins would be produced in the cold rolling process and their orientation also showed less deviation from ideal {001}<110> orientation when a raw material with a higher content of exact Goss oriented grains was used.

scholarly journals Crystallization of Polymers under the Influence of an External Force Field

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2078
Author(s):  
Rajdeep Singh Payal ◽  
Jens-Uwe Sommer
Keyword(s):  
External Force ◽  
Melting Behavior ◽  
Mechanical Work ◽  
Stem Length ◽  
Heat Of Fusion ◽  
Strong Increase ◽  
Lamellar Thickness ◽  
Equilibrium System ◽  
External Force Field ◽  
Work Done

We simulated the crystallization and melting behavior of entangled polymer melts using molecular dynamics where each chain is subject to a force dipole acting on its ends. This mimics the deformation of chains in a flow field but represents a well-defined equilibrium system in the melt state. Under weak extension within the linear response of the chains, the mechanical work done on the system is about two orders of magnitude smaller as compared with the heat of fusion. As a consequence, thermodynamic and simple arguments following the secondary nucleation model predict only small changes of the crystalline phase. By contrast, an increase of the stem length up to a factor of two is observed in our simulations. On the other hand, the lamellar thickening induced by the external force is proportional to the increase of the entanglement length in the melt prior to crystallization as measured by the primitive path method. While the mechanical work done on the system is only a small perturbation for thermodynamics of polymer crystallization, the change of the primitive path is large. This suggests that a strong increase in the lamellar thickness induced, by external deformation, a topological rather than a thermodynamic origin.

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