scholarly journals Force production capacity and functional reflex activity in young and elderly men

2010 ◽  
Vol 22 (5-6) ◽  
pp. 374-382 ◽  
Author(s):  
Urs Granacher ◽  
Markus Gruber ◽  
Albert Gollhofer
Keyword(s):  
Production Capacity ◽  
Force Production ◽  
Reflex Activity ◽  
Elderly Men

Force-length relation of isometric sarcomeres in fixed-end tetani

1993 ◽  
Vol 264 (1) ◽  
pp. C19-C26 ◽  
Author(s):  
A. Horowitz ◽  
G. H. Pollack
Keyword(s):  
Sarcomere Length ◽  
Production Capacity ◽  
Force Production ◽  
Length Change ◽  
Optical Diffraction ◽  
Tetanic Force ◽  
End Conditions ◽  
Linear Force ◽  
Fixed End

The higher force observed in fixed-end tetani relative to sarcomere-isometric tetani is commonly attributed to sarcomere length inhomogeneity; sarcomeres in the end regions of the fiber shorten extensively at the expense of the central sarcomeres. By shortening, these sarcomeres supposedly attain higher force production capacity and can thus account for the extra force. However, the fibers could also contain sarcomeres that stay isometric throughout most of the tetanic force plateau. If such sarcomeres undergo slight shortening before their isometric phase, their force-length relation should be elevated (A. Horowitz, H. P. M Wussling, and G. H. Pollack. Biophys. J. 63: 3-17, 1992). These sarcomeres may therefore account for the higher force in fixed-end tetani. To test this possibility, single frog semitendinosus fibers were tetanized under fixed-end conditions. Sarcomere length change during the tetanus was measured at different locations along the fiber by optical diffraction. Fibers stretched to average sarcomere lengths between 2.2 and 3.2 microns contained sarcomeres that, except for some initial shortening during the early part of the tetanus, remained isometric. These sarcomeres were located between the ends and the central region of the fibers. Their force-length relation was higher than the linear force-length relation based on sarcomere length clamps by an average of 14% between sarcomere lengths of 2.4-3.2 microns. Thus slight (1-5%) shortening may explain the relatively higher fixed-end force-length relation.

A Dynamic Escape Problem of Molecular Motors

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Dean Culver ◽  
Bryan Glaz ◽  
Samuel Stanton
Keyword(s):  
Molecular Motors ◽  
Binding Sites ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Three Dimensional ◽  
Production Capacity ◽  
Force Production ◽  
Actin Binding ◽  
Three Dimensional Model ◽  
Thermal Agitation

Abstract Animal skeletal muscle exhibits very interesting behavior at near-stall forces (when the muscle is loaded so strongly that it can barely contract). Near this physical limit, the myosin II proteins may be unable to reach advantageous actin binding sites through simple attractive forces. It has been shown that the advantageous utilization of thermal agitation is a likely source for an increased force-production capacity and reach in myosin-V (a processing motor protein), and here we explore the dynamics of a molecular motor without hand-over-hand motion including Brownian motion to show how local elastic energy well boundaries may be overcome. We revisit a spatially two-dimensional mechanical model to illustrate how thermal agitation can be harvested for useful mechanical work in molecular machinery inspired by this biomechanical phenomenon without rate functions or empirically inspired spatial potential functions. Additionally, the model accommodates variable lattice spacing, and it paves the way for a full three-dimensional model of cross-bridge interactions where myosin II may be azimuthally misaligned with actin binding sites. With potential energy sources based entirely on realizable components, this model lends itself to the design of artificial, molecular-scale motors.

scholarly journals Sprint Specificity of Isolated Hamstring-Strengthening Exercises in Terms of Muscle Activity and Force Production

2021 ◽  
Vol 2 ◽  
Author(s):  
Caroline Prince ◽  
Jean-Benoît Morin ◽  
Jurdan Mendiguchia ◽  
Johan Lahti ◽  
Kenny Guex ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Production Capacity ◽  
Force Production ◽  
Electromyographic Activity ◽  
Horizontal Force ◽  
Hamstring Muscle ◽  
Strengthening Exercises ◽  
Hip Flexion ◽  
Production Capacities ◽  
Hip Extension

To train hamstring muscle specifically to sprint, strengthening programs should target exercises associated with horizontal force production and high levels of hamstring activity. Therefore, the objectives of this study were to analyze the correlation between force production capacities during sprinting and hamstring strengthening exercises, and to compare hamstring muscle activity during sprinting and these exercises. Fourteen track and field regional level athletes performed two maximal 50-m sprints and six strengthening exercises: Nordic hamstring exercises without and with hip flexion, Upright-hip-extension in isometric and concentric modalities, Standing kick, and Slide-leg-bridge. The sprinting horizontal force production capacity at low (F0) and high (V0) speeds was computed from running velocity data. Hamstring muscle performances were assessed directly or indirectly during isolated exercises. Hamstring muscle electromyographic activity was recorded during all tasks. Our results demonstrate substantially large to very large correlations between V0 and performances in the Upright-hip-extension in isometric (rs = 0.56; p = 0.040), Nordic hamstring exercise without hip flexion (rs = 0.66; p = 0.012) and with 90° hip flexion (rs = 0.73; p = 0.003), and between F0 and Upright-hip-extension in isometric (rs = 0.60; p = 0.028) and the Nordic hamstring exercise without hip flexion (rs = 0.59; p = 0.030). However, none of the test exercises activated hamstring muscles more than an average of 60% of the maximal activation during top-speed sprinting. In conclusion, training programs aiming to be sprint-specific in terms of horizontal force production could include exercises such as the Upright-hip-extension and the Nordic hamstring exercise, in addition to maximal sprinting activity, which is the only exercise leading to high levels of hamstring muscle activity.

scholarly journals Association between rapid force production by the plantar flexors and balance performance in elderly men and women

AGE ◽  
2016 ◽  
Vol 38 (5-6) ◽  
pp. 475-483 ◽  
Author(s):  
Ryoichi Ema ◽  
Megumi Saito ◽  
Shunsuke Ohki ◽  
Hirokazu Takayama ◽  
Yosuke Yamada ◽  
...  
Keyword(s):  
Force Production ◽  
Plantar Flexors ◽  
Balance Performance ◽  
Elderly Men ◽  
Men And Women

scholarly journals Does Living and Working in a Hot Environment Induce Clinically Relevant Changes in Immune Function and Voluntary Force Production Capacity?

2014 ◽  
Vol 52 (3) ◽  
pp. 235-239 ◽  
Author(s):  
Wade KNEZ ◽  
Olivier GIRARD ◽  
Sebastien RACINAIS ◽  
Andrew WALSH ◽  
Nadia GAOUA ◽  
...  
Keyword(s):  
Immune Function ◽  
Production Capacity ◽  
Force Production ◽  
Hot Environment

Leg extensor muscle voluntary isometric force production capacity in children with spastic diplegia

2012 ◽  
Vol 15 ◽  
pp. 48
Author(s):  
Mati Pääsuke ◽  
Krista Kuresson ◽  
Helena Gapeyeva ◽  
Jaan Ereline ◽  
Tatjana Kums ◽  
...  
Keyword(s):  
Isometric Force ◽  
Production Capacity ◽  
Force Production ◽  
Extensor Muscle ◽  
Spastic Diplegia ◽  
Isometric Force Production

Maximal and explosive force production capacity and balance performance in men of different ages

1999 ◽  
Vol 79 (3) ◽  
pp. 260-267 ◽  
Author(s):  
M. Izquierdo ◽  
X. Aguado ◽  
R. Gonzalez ◽  
J. L. L�pez ◽  
K. H�kkinen
Keyword(s):  
Production Capacity ◽  
Force Production ◽  
Balance Performance ◽  
Different Ages ◽  
Explosive Force
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