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https://www.readbyqxmd.com/read/27913559/physical-activity-as-intervention-for-age-related-loss-of-muscle-mass-and-function-protocol-for-a-randomised-controlled-trial-the-lisa-study
#1
Christian Skou Eriksen, Ellen Garde, Nina Linde Reislev, Cathrine Lawaetz Wimmelmann, Theresa Bieler, Andreas Kraag Ziegler, Anne Theil Gylling, Kasper Juel Dideriksen, Hartwig Roman Siebner, Erik Lykke Mortensen, Michael Kjaer
INTRODUCTION: Physical and cognitive function decline with age, accelerating during the 6th decade. Loss of muscle power (force×velocity product) is a dominant physical determinant for loss of functional ability, especially if the lower extremities are affected. Muscle strength training is known to maintain or even improve muscle power as well as physical function in older adults, but the optimal type of training for beneficial long-term training effects over several years is unknown...
December 2, 2016: BMJ Open
https://www.readbyqxmd.com/read/27896682/methods-of-power-force-velocity-profiling-during-sprint-running-a-narrative-review
#2
REVIEW
Matt R Cross, Matt Brughelli, Pierre Samozino, Jean-Benoit Morin
The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting...
November 28, 2016: Sports Medicine
https://www.readbyqxmd.com/read/27864330/three-dimensional-stochastic-model-of-actin-myosin-binding-in-the-sarcomere-lattice
#3
Srboljub M Mijailovich, Oliver Kayser-Herold, Boban Stojanovic, Djordje Nedic, Thomas C Irving, Michael A Geeves
The effect of molecule tethering in three-dimensional (3-D) space on bimolecular binding kinetics is rarely addressed and only occasionally incorporated into models of cell motility. The simplest system that can quantitatively determine this effect is the 3-D sarcomere lattice of the striated muscle, where tethered myosin in thick filaments can only bind to a relatively small number of available sites on the actin filament, positioned within a limited range of thermal movement of the myosin head. Here we implement spatially explicit actomyosin interactions into the multiscale Monte Carlo platform MUSICO, specifically defining how geometrical constraints on tethered myosins can modulate state transition rates in the actomyosin cycle...
December 2016: Journal of General Physiology
https://www.readbyqxmd.com/read/27824440/nonlinear-response-of-inertial-tracers-in-steady-laminar-flows-differential-and-absolute-negative-mobility
#4
A Sarracino, F Cecconi, A Puglisi, A Vulpiani
We study the mobility and the diffusion coefficient of an inertial tracer advected by a two-dimensional incompressible laminar flow, in the presence of thermal noise and under the action of an external force. We show, with extensive numerical simulations, that the force-velocity relation for the tracer, in the nonlinear regime, displays complex and rich behaviors, including negative differential and absolute mobility. These effects rely upon a subtle coupling between inertia and applied force that induces the tracer to persist in particular regions of phase space with a velocity opposite to the force...
October 21, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27806673/sprint-performance-and-mechanical-outputs-computed-with-an-iphone-app-comparison-with-existing-reference-methods
#5
Natalia Romero-Franco, Pedro Jiménez-Reyes, Adrián Castaño-Zambudio, Fernando Capelo-Ramírez, Juan José Rodríguez-Juan, Jorge González-Hernández, Francisco Javier Toscano-Bendala, Víctor Cuadrado-Peñafiel, Carlos Balsalobre-Fernández
The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al...
November 3, 2016: European Journal of Sport Science
https://www.readbyqxmd.com/read/27705034/the-high-pull-exercise-a-comparison-between-a-versapulley-flywheel-device-and-the-free-weight
#6
F Javier Núñez, Luis J Suarez-Arrones, Paul Cater, Alberto Mendez-Villanueva
The aim of this study was to examine the kinematics and kinetics (force, velocity and acceleration) and blood lactate concentration of the Versapulley (VP) device in comparison with free weight (FW) exercise at a similar external load. Fifteen rugby players randomly performed two training sessions of 6 sets of 6 repetitions with 20 s of recovery in between sets of the high pull exercise with the VP and the FW. Both training sessions were separated by 72 h. Barbell displacement (cm.), peak velocity (m/s), peak acceleration (m/s(2)), mean propulsive velocity (m/s), mean propulsive acceleration (m/s(2)), propulsive phase (%), mean and maximal force (Newtons) were continuously recorded during each repetition...
September 6, 2016: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/27676816/hamstring-injury-prevention-contributions-of-biomechanics
#7
Pascal Edouard, Pierre Samozino, Romain Slotala, Jurdan Mendiguchia, Jean-Benoit Morin
Hamstring muscle injury is the main injury related to athletics, but also other sports including acceleration and sprints, with important consequences (time loss of sport and re-injury risk). In a prevention approach, a better knowledge of risk factors and mechanisms of these lesions seem relevant, and it can pass through a better understanding of the biomechanical and muscular determinants of performance in sprint and acceleration. The ability to produce a horizontal force on the ground [i.e. orienting the total push backward (or ground force reaction forward)], and to do so despite the increase in running speed, is an important determinant of sprint performance...
September 2016: Annals of Physical and Rehabilitation Medicine
https://www.readbyqxmd.com/read/27669187/muscle-specific-effective-mechanical-advantage-and-joint-impulse-in-weightlifting
#8
Kristof Kipp, Chad Harris
Lifting greater loads during weightlifting exercises may theoretically be achieved through increasing the magnitudes of net joint impulses or manipulating the joints' effective mechanical advantage (EMA). The purpose of this study was to investigate muscle-specific EMA and joint impulse as well as impulse-momentum characteristics of the lifter-barbell system across a range of external loads during the execution of the clean. Collegiate-level weightlifters performed sub-maximal cleans at 65, 75, and 85% of their 1-repetition maximum (1-RM) while data from a motion analysis system and a force plate were used to calculate lifter-barbell system impulse and velocity, as well as net extensor impulse generated at the hip, knee, and ankle joints and the EMA of the gluteus maximus, hamstrings, quadriceps, and triceps surae muscles...
September 21, 2016: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/27618131/the-high-pull-exercise-a-comparison-between-a-versapulley-flywheel-device-and-the-free-weight
#9
F Javier Núñez, Luis J Suarez-Arrones, Paul Cater, Alberto Mendez-Villanueva
The aim of this study was to examine the kinematics and kinetics (force, velocity and acceleration) and blood lactate concentration of the Versapulley (VP) device in comparison with free weight (FW) exercise at a similar external load. Fifteen rugby players randomly performed two training sessions of 6 sets of 6 repetitions with 20 s of recovery in between sets of the high pull exercise with the VP and the FW. Both training sessions were separated by 72 h. Barbell displacement (cm.), peak velocity (m/s), peak acceleration (m/s2), mean propulsive velocity (m/s), mean propulsive acceleration (m/s2), propulsive phase (%), mean and maximal force (Newtons) were continuously recorded during each repetition...
September 6, 2016: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/27582260/bilateral-deficit-in-maximal-force-production
#10
Jakob Škarabot, Neil Cronin, Vojko Strojnik, Janne Avela
The bilateral deficit phenomenon, characterized by a reduction in the amount of force from a single limb during maximal bilateral actions, has been shown in various movement tasks, contraction types and different populations. However, bilateral deficit appears to be an inconsistent phenomenon, with high variability in magnitude and existence, and seems to be plastic, as bilateral facilitation has also been shown to occur. Furthermore, many mechanisms underlying this phenomenon have been proposed over the years, but still remain largely unknown...
August 31, 2016: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/27577950/1rm-prediction-a-novel-methodology-based-on-the-force-velocity-and-load-velocity-relationships
#11
Pietro Picerno, Danilo Iannetta, Stefania Comotto, Marco Donati, Fabrizio Pecoraro, Mounir Zok, Giorgio Tollis, Marco Figura, Carlo Varalda, Davide Di Muzio, Federica Patrizio, Maria Francesca Piacentini
PURPOSE: This study aimed to evaluate the accuracy of a novel approach for predicting the one-repetition maximum (1RM). The prediction is based on the force-velocity and load-velocity relationships determined from measured force and velocity data collected during resistance-training exercises with incremental submaximal loads. 1RM was determined as the load corresponding to the intersection of these two curves, where the gravitational force exceeds the force that the subject can exert...
October 2016: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/27548784/acute-kinematic-and-kinetic-adaptations-to-wearable-resistance-during-sprint-acceleration
#12
Paul Macadam, Kim D Simperingham, John B Cronin
Wearable resistance (WR) in the form of weighted vests and shorts enables movement specific sprint running to be performed under load. The purpose of this study was to determine the acute changes in kinematics and kinetics when an additional load equivalent to 3% body mass (BM) was attached to the anterior or posterior surface of the lower limbs during sprint running. Nineteen male rugby athletes (age: 19.7 ± 2.3 years; body mass: 96.1 ± 16.5 kg; height: 181 ± 6.5 cm) volunteered to participate in the study...
August 18, 2016: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/27541062/a-simple-method-for-assessment-of-muscle-force-velocity-and-power-producing-capacities-from-functional-movement-tasks
#13
Milena Z Zivkovic, Sasa Djuric, Ivan Cuk, Dejan Suzovic, Slobodan Jaric
A range of force (F) and velocity (V) data obtained from functional movement tasks (e.g., running, jumping, throwing, lifting, cycling) performed under variety of external loads have typically revealed strong and approximately linear F-V relationships. The regression model parameters reveal the maximum F (F-intercept), V (V-intercept), and power (P) producing capacities of the tested muscles. The aim of the present study was to evaluate the level of agreement between the routinely used "multiple-load model" and a simple "two-load model" based on direct assessment of the F-V relationship from only 2 external loads applied...
August 19, 2016: Journal of Sports Sciences
https://www.readbyqxmd.com/read/27537408/the-maximal-mechanical-capabilities-of-leg-extensors-muscles-to-generate-velocity-and-power-improve-at-altitude
#14
Amador García-Ramos, Igor Štirn, Paulino Padial, Javier Argüelles-Cienfuegos, Blanca De la Fuente, Vojko Strojnik, Belén Feriche
This study aimed (a) to analyze the effect of an acute exposure to terrestrial altitude on the force-velocity relationship parameters (maximum force [F0)], maximum velocity [V0)], and maximum power [P0)]) during a loaded squat jump (SJ), and (b) to compare unloaded SJ and countermovement jump (CMJ) performance between sea level and altitude conditions. Seventeen international swimmers were tested at sea level (295 m asl) and 7 days later at terrestrial altitude (2320 m asl) during their first 24 hours of altitude exposure...
August 16, 2016: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/27493196/modeling-age-related-changes-in-muscle-tendon-dynamics-during-cyclical-contractions-in-the-rat-gastrocnemius
#15
Nicole Danos, Natalie C Holt, Gregory S Sawicki, Emanuel Azizi
Efficient muscle-tendon performance during cyclical tasks is dependent on both active and passive mechanical tissue properties. Here we examine whether age-related changes in the properties of muscle-tendon units (MTUs) compromise their ability to do work and utilize elastic energy storage. We empirically quantified passive and active properties of the medial gastrocnemius muscle and material properties of the Achilles tendon in young (~6 mos) and old (~32 mos) rats. We then used these properties in computer simulations of a Hill-type muscle model in series with a Hookean spring...
August 4, 2016: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27492179/in-vitro-assays-to-determine-skeletal-muscle-physiologic-function
#16
Justin E Sperringer, Robert W Grange
In vitro muscle contractile function assays are important to characterize the differences between different muscle types (e.g., slow vs. fast), between a diseased and non-diseased muscle, or importantly, to demonstrate the efficacy of a muscle treatment such as a drug, an overexpressed transgene, or knockout of a specific gene. Fundamental contractile properties can be assessed by twitch, tetanic, force-frequency, force-velocity, and fatigue assays. Many of these assays are conducted with the muscle at a constant length, e...
2016: Methods in Molecular Biology
https://www.readbyqxmd.com/read/27472485/a-model-of-muscle-contraction-based-on-the-langevin-equation-with-actomyosin-potentials
#17
Youjiro Tamura, Akira Ito, Masami Saito
We propose a muscle contraction model that is essentially a model of the motion of myosin motors as described by a Langevin equation. This model involves one-dimensional numerical calculations wherein the total force is the sum of a viscous force proportional to the myosin head velocity, a white Gaussian noise produced by random forces and other potential forces originating from the actomyosin structure and intra-molecular charges. We calculate the velocity of a single myosin on an actin filament to be 4.9-49 μm/s, depending on the viscosity between the actomyosin molecules...
July 29, 2016: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/27417976/adding-stiffness-to-the-foot-modulates-soleus-force-velocity-behaviour-during-human-walking
#18
Kota Z Takahashi, Michael T Gross, Herman van Werkhoven, Stephen J Piazza, Gregory S Sawicki
Previous studies of human locomotion indicate that foot and ankle structures can interact in complex ways. The structure of the foot defines the input and output lever arms that influences the force-generating capacity of the ankle plantar flexors during push-off. At the same time, deformation of the foot may dissipate some of the mechanical energy generated by the plantar flexors during push-off. We investigated this foot-ankle interplay during walking by adding stiffness to the foot through shoes and insoles, and characterized the resulting changes in in vivo soleus muscle-tendon mechanics using ultrasonography...
2016: Scientific Reports
https://www.readbyqxmd.com/read/27415305/actin-filaments-growing-against-a-barrier-with-fluctuating-shape
#19
Raj Kumar Sadhu, Sakuntala Chatterjee
We study force generation by a set of parallel actin filaments growing against a nonrigid obstacle, in the presence of an external load. The filaments polymerize by either moving the whole obstacle, with a large energy cost, or by causing local distortion in its shape which costs much less energy. The nonrigid obstacle also has local thermal fluctuations due to which its shape can change with time and we describe this using fluctuations in the height profile of a one-dimensional interface with Kardar-Parisi-Zhang dynamics...
June 2016: Physical Review. E
https://www.readbyqxmd.com/read/27414690/sprint-acceleration-mechanics-in-master-athletes
#20
Patricia D Pantoja, Eduardo Saez de Villarreal, Jeanick Brisswalter, Leonardo A Peyré-Tartaruga, Jean-Benoit Morin
PURPOSE: The best sprint performances are usually reached between the ages of 20 and 30; however even in well-trained individuals, performance continues to decrease with age. While this inevitable decrease in performance has been related to reductions in muscular force, velocity and power capabilities, these measures have not been assessed in the specific context of sprinting. The aim of this study was to investigate the mechanical outputs of sprinting acceleration among Masters sprinters to better understand the mechanical underpinnings of the age-related decrease in sprint performance...
July 12, 2016: Medicine and Science in Sports and Exercise
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