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https://www.readbyqxmd.com/read/29129132/reliability-of-force-velocity-relationships-during-deadlift-high-pull
#1
Wei Lu, Sébastien Boyas, Marc Jubeau, Abderrahmane Rahmani
This study aimed to evaluate the within- and between-session reliability of force, velocity and power performances and to assess the force-velocity relationship during the deadlift high pull (DHP). Nine participants performed two identical sessions of DHP with loads ranging from 30 to 70% of body mass. The force was measured by a force plate under the participants' feet. The velocity of the 'body + lifted mass' system was calculated by integrating the acceleration and the power was calculated as the product of force and velocity...
November 13, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/29126339/the-force-velocity-relationship-in-older-people-reliability-and-validity-of-a-systematic-procedure
#2
Julian Alcazar, Carlos Rodriguez-Lopez, Ignacio Ara, Ana Alfaro-Acha, Asier Mañas-Bote, Amelia Guadalupe-Grau, Francisco Jose García-García, Luis M Alegre
This study compared the reliability and validity of different protocols evaluating the force-velocity (F-V) relationship and muscle power in older adults. Thirty-one older men and women (75.8±4.7 years) underwent two F-V tests by collecting the mean and peak force and velocity data exerted against increasing loads until one repetition maximum (1RM) was achieved in the leg press exercise. Two attempts per load were performed, with a third attempt when F-V points deviated from the linear F-V regression equation...
November 10, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/29125040/reliability-of-horizontal-force-velocity-power-profiling-during-short-sprint-running-accelerations-using-radar-technology
#3
Kim David Simperingham, John B Cronin, Simon N Pearson, Angus Ross
Radar technology can be used to perform horizontal force-velocity-power profiling during sprint-running. The aim of this study was to determine the reliability of radar-derived profiling results from short sprint accelerations. Twenty-seven participants completed three 30 m sprints (intra-day analysis), and nine participants completed the testing session on four separate days (inter-day analysis). The majority of radar-derived kinematic and kinetic descriptors of short sprint performance had acceptable intra-day and inter-day reliability [intraclass correlation coefficient (ICC) ≥ 0...
November 10, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/29101912/effect-of-hip-joint-angle-on-concentric-knee-extension-torque
#4
Ryoichi Ema, Taku Wakahara, Yasuo Kawakami
This study tested the hypothesis that the effect of hip joint angle on concentric knee extension torque depends on knee joint angle during a single knee extension task. Twelve men performed concentric knee extensions in fully extended and 80° flexed hip positions with maximal effort. The angular velocities were set at 30° s(-1) and 180° s(-1). The peak torque and torques attained at 30°, 50°, 70° and 90° (anatomical position = 0°) of the knee joint were compared between the two hip positions...
October 26, 2017: Journal of Electromyography and Kinesiology
https://www.readbyqxmd.com/read/29093684/porcine-stomach-smooth-muscle-force-depends-on-history-effects
#5
André Tomalka, Mischa Borsdorf, Markus Böl, Tobias Siebert
The stomach serves as food reservoir, mixing organ and absorption area for certain substances, while continually varying its position and size. Large dimensional changes during ingestion and gastric emptying of the stomach are associated with large changes in smooth muscle length. These length changes might induce history-effects, namely force depression (FD) following active muscle shortening and force enhancement (FE) following active muscle stretch. Both effects have impact on the force generating capacity of the stomach, and thus functional relevance...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/29089109/explosive-lower-limb-extension-mechanics-an-on-land-vs-in-water-exploratory-comparison
#6
Brice Guignard, Jessy Lauer, Pierre Samozino, Luis Mourão, João Paulo Vilas-Boas, Annie Hélène Rouard
During a horizontal underwater push-off, performance is strongly limited by the presence of water, inducing resistances due to its dense and viscous nature. At the same time, aquatic environments offer a support to the swimmer with the hydrostatic buoyancy counteracting the effects of gravity. Squat jump is a vertical terrestrial push-off with a maximal lower limb extension limited by the gravity force, which attracts the body to the ground. Following this observation, we characterized the effects of environment (water vs...
October 25, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29076192/regional-variation-in-the-mechanical-properties-and-fibre-type-composition-of-the-rat-extensor-digitorum-longus-muscle
#7
Roger W P Kissane, Stuart Egginton, Graham N Askew
Fibre type composition is heterogeneous and distribution varies spatially in many muscles, indicating there may be regional variation in recruitment and mechanical output. The rat extensor digitorum longus muscle is composed of predominantly fast-twitch fibres, and exhibits a gradient in phenotype, resulting in oxidative medial (areal composition 24.3% Type I/IIa) and glycolytic lateral (92.4% Type IIx/IIb) compartments. Here, we investigated the variation in mechanical performance between the medial and lateral compartments during isometric, isotonic and cyclical contractions...
October 26, 2017: Experimental Physiology
https://www.readbyqxmd.com/read/29050041/lower-limb-force-velocity-power-capabilities-during-leg-press-and-squat-movements
#8
Johnny Padulo, Gian Mario Migliaccio, Luca Paolo Ardigò, Bruno Leban, Marco Cosso, Pierre Samozino
The aim was to compare lower-limb power, force, and velocity capabilities between squat and leg press movements. Ten healthy sportsmen performed ballistic lower-limb push-offs against 5-to-12 different loads during both the squat and leg press. Individual linear force-velocity and polynomial power-velocity relationships were determined for both movements from push-off mean force and velocity measured continuously with a pressure sensor and linear encoder. Maximal power output, theoretical maximal force and velocity, force-velocity profile and optimal velocity were computed...
October 19, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28976526/cooperative-behavior-of-biased-probes-in-crowded-interacting-systems
#9
Oleg A Vasilyev, Olivier Bénichou, Carlos Mejía-Monasterio, Eric R Weeks, Gleb Oshanin
We study, via extensive numerical simulations, dynamics of a crowded mixture of mutually interacting (with a short-range repulsive potential) colloidal particles immersed in a suspending solvent, acting as a heat bath. The mixture consists of a majority component - neutrally buoyant colloids subject to internal stimuli only, and a minority component - biased probes (BPs) also subject to a constant force. In such a system each of the BPs alters the distribution of the colloidal particles in its vicinity, driving their spatial distribution out of equilibrium...
October 25, 2017: Soft Matter
https://www.readbyqxmd.com/read/28972685/effects-of-manipulating-tetanic-calcium-on-the-curvature-of-the-force-velocity-relationship-in-isolated-rat-soleus-muscles
#10
A M Kristensen, O B Nielsen, K Overgaard
AIM: In dynamically contracting muscles, increased curvature of the force-velocity relationship contributes to the loss of power during fatigue. It has been proposed that fatigue-induced reduction in [Ca(++) ]i causes this increased curvature. However, earlier studies on single fibers have been conducted at low temperatures. Here, we investigated the hypothesis that curvature is increased by reductions in tetanic [Ca(++) ]i in isolated skeletal muscle at near-physiological temperatures...
October 3, 2017: Acta Physiologica
https://www.readbyqxmd.com/read/28965345/relationship-between-force-velocity-profiles-and-1-500-m-ergometer-performance-in-young-rowers
#11
Caroline Giroux, Hugo Maciejewski, Amal Ben-Abdessamie, Frédéric Chorin, Julien Lardy, Sebastien Ratel, Abderrahmane Rahmani
Rowing races require developing high level of force and power output at high contraction velocity. This study determined the force-velocity and power-velocity (F-P-V) profiles of lower and upper limbs of adolescent rowers and their relationships with a 1,500-m rowing ergometer performance. The power developed during the 1,500-m (P1500) was evaluated in fourteen national-level male rowers (age: 15.3±0.6 yrs). F-P-V profiles were assessed during bench pull (BP) and squat jump (SJ) exercises. The theoretical maximal values of force (F0), velocity (V0), power output (Pmax) and the F-V relationship slope (S FV ) were determined...
October 1, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28965339/where-does-the-one-repetition-maximum-exist-on-the-force-velocity-relationship-in-squat
#12
Jean Romain Rivière, Jérémy Rossi, Pedro Jimenez-Reyes, Jean-Benoit Morin, Pierre Samozino
The aim was to determine the position of the one-repetition maximum (1RM) squat point on the force-velocity (F-V) relationship obtained during squat jump (SJ). Ten healthy athletes performed a 1RM squat during which ground reaction force and lower-limb extension velocity were measured, and six loaded SJs to determine individual F-V relationship. The goodness of fit of the linear F-V relationship with or without the 1RM point was tested. The vertical and horizontal coordinates were determined relative to the theoretical maximal force (F0) and the highest loaded SJ (load of 44...
October 1, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28952867/optimal-resistive-forces-for-maximizing-the-reliability-of-leg-muscles-capacities-tested-on-a-cycle-ergometer
#13
Amador García-Ramos, Alejandro Torrejón, Antonio J Morales-Artacho, Alejandro Pérez-Castilla, Slobodan Jaric
This study determined the optimal resistive forces for testing muscle capacities through the standard cycle ergometer test (one resistive force applied) and a recently developed two-point method (two resistive forces used for force-velocity modelling). Twenty-six men were tested twice on maximal sprints performed on a leg cycle ergometer against 5 flywheel resistive forces (R1-R5). The reliability of the cadence and maximum power measured against the 5 individual resistive forces, as well as the reliability of the force-velocity relationship parameters obtained from the selected two-point methods (R1-R2, R1-R3, R1-R4, and R1-R5) were compared...
September 27, 2017: Journal of Applied Biomechanics
https://www.readbyqxmd.com/read/28942558/anomalous-force-velocity-relation-of-driven-inertial-tracers-in-steady-laminar-flows
#14
F Cecconi, A Puglisi, A Sarracino, A Vulpiani
We study the nonlinear response to an external force of an inertial tracer advected by a two-dimensional incompressible laminar flow and subject to thermal noise. In addition to the driving external field F, the main parameters in the system are the noise amplitude [Formula: see text] and the characteristic Stokes time [Formula: see text] of the tracer. The relation velocity vs. force shows interesting effects, such as negative differential mobility (NDM), namely a non-monotonic behavior of the tracer velocity as a function of the applied force, and absolute negative mobility (ANM), i...
September 2017: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/28901373/kinesin-and-dynein-mechanics-measurement-methods-and-research-applications
#15
Zachary Abraham, Emma Hawley, Daniel Hayosh, Victoria Webster-Wood, Ozan Akkus
Motor proteins play critical roles in the normal function of cells and proper development of organisms. Among motor proteins, failings in the normal function of two types of proteins, kinesin and dynein, have been shown to lead many pathologies, including neurodegenerative diseases and cancers. As such, it is critical for researchers to understand the underlying mechanics and behaviors of these proteins, not only to shed light on how failures may lead to disease, but also to guide research towards novel treatment and nanoengineering solutions...
September 13, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/28892463/effect-of-different-velocity-loss-thresholds-during-a-power-oriented-resistance-training-program-on-the-mechanical-capacities-of-lower-body-muscles
#16
Alejandro Pérez-Castilla, Amador García-Ramos, Paulino Padial, Antonio J Morales-Artacho, Belén Feriche
This study compared the effects of two velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles. Twenty men were counterbalanced in two groups (VL10 and VL20) based on their maximum power capacity. Both groups used the same exercises, relative intensity and repetition volume, only differing in the velocity loss threshold of each set (VL10: 10% vs. VL20: 20%). Pre- and post-training assessments included an incremental loading test and a 15-m linear sprint to assess the force- and load-velocity relationships and athletic performance variables, respectively...
September 11, 2017: Journal of Sports Sciences
https://www.readbyqxmd.com/read/28872389/training-related-changes-in-force-power-profiles-implications-for-the-skeleton-start
#17
Steffi L Colyer, Keith A Stokes, James L J Bilzon, Danny Holdcroft, Aki I T Salo
PURPOSE: Athletes' force-power characteristics influence sled velocity during the skeleton start, which is a crucial determinant of performance. This study characterised force-power profile changes across an 18-month period and investigated the associations between these changes and start performance. METHODS: Seven elite- and five talent-squad skeleton athletes' (representing 80% of registered athletes in the country) force-power profiles and dry-land push-track performances were assessed at multiple time-points over two 6-month training periods and one 5-month competition season...
September 5, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28872385/new-records-in-human-power
#18
Thomas Haugen, Gøran Paulsen, Stephen Seiler, Øyvind Sandbakk
Maximal aerobic and anaerobic power are crucial performance determinants in most sports disciplines. Numerous studies have published power data from elite athletes over the years, particularly in runners, cyclists, rowers and cross-country skiers. In this invited review, we define the current "world records" in human upper limits of aerobic and anaerobic power. Currently, V̇O2max values of ~7.5 and 7.0 L·min(-1) in male cross-country (XC) skiers and rowers, respectively, and/or ~90 ml·kg(-1)·min(-1) in XC skiers, cyclists and runners can be described as upper human limits for aerobic power...
September 5, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28865494/implementation-and-validation-of-the-extended-hill-type-muscle-model-with-robust-routing-capabilities-in-ls-dyna-for-active-human-body-models
#19
Christian Kleinbach, Oleksandr Martynenko, Janik Promies, Daniel F B Haeufle, Jörg Fehr, Syn Schmitt
BACKGROUND: In the state of the art finite element AHBMs for car crash analysis in the LS-DYNA software material named *MAT_MUSCLE (*MAT_156) is used for active muscles modeling. It has three elements in parallel configuration, which has several major drawbacks: restraint approximation of the physical reality, complicated parameterization and absence of the integrated activation dynamics. This study presents implementation of the extended four element Hill-type muscle model with serial damping and eccentric force-velocity relation including [Formula: see text] dependent activation dynamics and internal method for physiological muscle routing...
September 2, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28860176/shifting-gears-dynamic-muscle-shape-changes-and-force-velocity-behaviour-in-the-medial-gastrocnemius
#20
Taylor Jessica Marie Dick, James Michael Wakeling
When muscles contract, they bulge in thickness or in width to maintain a (nearly) constant volume. These dynamic shape changes are tightly linked to the internal constraints placed on individual muscle fibres and play a key functional role in modulating the mechanical performance of skeletal muscle by increasing its range of operating velocities. Yet to date, we have a limited understanding of the nature and functional implications of in vivo dynamic muscle shape change under submaximal conditions. This study determined how the in vivo changes in medial gastrocnemius (MG) fascicle velocity, pennation angle, muscle thickness and subsequent muscle gearing varied as a function of force and velocity...
August 31, 2017: Journal of Applied Physiology
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