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"Force-velocity"

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https://www.readbyqxmd.com/read/28632047/reliability-and-magnitude-of-mechanical-variables-assessed-from-unconstrained-and-constrained-loaded-countermovement-jumps
#1
Amador García-Ramos, Slobodan Jaric, Alejandro Pérez-Castilla, Paulino Padial, Belén Feriche
This study aimed to (1) assess the reliability of the force, velocity, and power output variables measured by a force plate and a linear velocity transducer (LVT) for both the unconstrained and constrained loaded countermovement jump (CMJ), and (2) examine the effect of both the CMJ type and the measurement method on the magnitudes of the same variables. Twenty-three men were tested on the free CMJ and the CMJ constrained by a Smith machine. Maximum values of force, velocity, and power were recorded by a force plate and by a LVT attached to a bar loaded by 17, 30, 45, 60, and 75 kg...
February 24, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28605252/a-simple-method-for-assessing-upper-limb-force-velocity-profile-in-bench-press
#2
Abderrahmane Rahmani, Pierre Samozino, Jean-Benoit Morin, Baptiste Morel
PURPOSE: 1) to analyze the reliability and validity of a field computation method based on easy-to-measure data to assess the mean force (F̄) and velocity (v̄) produced during a ballistic bench press movement; and 2) to verify that the force-velocity profile (F-v) obtained with multiple loaded trials is accurately described. METHODS: Twelve participants performed ballistic bench press against various lifted mass from 30 to 70% of their body mass. For each trial, F̄ and v̄ were determined from an accelerometer (sampling rate: 500Hz; reference method) and a simple computation method based on upper limb mass, barbell flight height and push-off distance...
June 12, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28605214/influence-of-reactive-strength-index-modified-on-force-and-power-time-curves
#3
John J McMahon, Paul A Jones, Timothy J Suchomel, Jason Lake, Paul Comfort
PURPOSE: The reactive strength index modified (RSImod) has been recently identified and validated as a method of monitoring countermovement jump (CMJ) performance. The kinetic and kinematic mechanisms that optimize a higher RSImod score are, however, currently unknown. The purpose of this study, therefore, was to compare entire CMJ force-, power-, velocity- and displacement-time curves (termed temporal phase analysis) of athletes who achieve high versus low RSImod scores. METHODS: Fifty-three professional male rugby league players performed three maximal effort CMJs on a force platform and variables of interest were calculated via forward dynamics...
June 12, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28584973/from-single-muscle-fiber-to-whole-muscle-mechanics-a-finite-element-model-of-a-muscle-bundle-with-fast-and-slow-fibers
#4
Lorenzo Marcucci, Carlo Reggiani, Arturo N Natali, Piero G Pavan
Muscles exhibit highly complex, multi-scale architecture with thousands of muscle fibers, each with different properties, interacting with each other and surrounding connective structures. Consequently, the results of single-fiber experiments are scarcely linked to the macroscopic or whole muscle behavior. This is especially true for human muscles where it would be important to understand of how skeletal muscles disorders affect patients' life. In this work, we developed a mathematical model to study how fast and slow muscle fibers, well characterized in single-fiber experiments, work and generate together force and displacement in muscle bundles...
June 5, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28579649/a-viscoactive-constitutive-modeling-framework-with-variational-updates-for-the-myocardium
#5
A V S Ponnaluri, L E Perotti, D B Ennis, W S Klug
We present a constitutive modeling framework for contractile cardiac mechanics by formulating a single variational principle from which incremental stress-strain relations and kinetic rate equations for active contraction and relaxation can all be derived. The variational framework seamlessly incorporates the hyperelastic behavior of the relaxed and contracted tissue along with the rate - and length - dependent generation of contractile force. We describe a three-element, Hill-type model that unifies the active tension and active deformation approaches...
February 1, 2017: Computer Methods in Applied Mechanics and Engineering
https://www.readbyqxmd.com/read/28573027/operating-length-and-velocity-of-human-m-vastus-lateralis-fascicles-during-vertical-jumping
#6
Maria Elissavet Nikolaidou, Robert Marzilger, Sebastian Bohm, Falk Mersmann, Adamantios Arampatzis
Humans achieve greater jump height during a counter-movement jump (CMJ) than in a squat jump (SJ). However, the crucial difference is the mean mechanical power output during the propulsion phase, which could be determined by intrinsic neuro-muscular mechanisms for power production. We measured M. vastus lateralis (VL) fascicle length changes and activation patterns and assessed the force-length, force-velocity and power-velocity potentials during the jumps. Compared with the SJ, the VL fascicles operated on a more favourable portion of the force-length curve (7% greater force potential, i...
May 2017: Royal Society Open Science
https://www.readbyqxmd.com/read/28552929/correlations-between-somatic-features-anteroposterior-spinal-curvatures-and-trunk-muscle-strength-in-schoolchildren
#7
Katarzyna Barczyk-Pawelec, Wioletta Dziubek, Jerzy R Piechura, Krystyna Rożek
BACKGROUND: Evaluation of body posture and strength of spinal muscles in children during their progressive ontogenesis is significant for the evaluation of their physical health condition and physical fitness. It is also a reference point in a process of control and medical care. PURPOSE: The aim if this study was to evaluate correlation between the selected features of somatic body structure, shape of anteroposterior spinal curves and force-velocity (FV) parameters of trunk muscles in school children...
2017: Acta of Bioengineering and Biomechanics
https://www.readbyqxmd.com/read/28530478/validity-of-a-linear-velocity-transducer-for-testing-maximum-vertical-jumps
#8
Alejandro Pérez-Castilla, Belén Feriche, Slobodan Jaric, Paulino Padial, Amador García-Ramos
This study aimed to examine the validity of mechanical variables obtained by a linear velocity transducer from the unconstrained and constrained squat jump (SJ). Twenty-three men were tested on the unconstrained SJ and the SJ constrained by a Smith machine. Maximum values of force, velocity, and power were simultaneously recorded both by a linear velocity transducer attached to a bar of mass of 17, 30, 45, 60 and 75 kg and by a force plate. Linear velocity transducer generally overestimated the outcomes measured as compared to the force plate, particularly in unconstrained SJ...
May 22, 2017: Journal of Applied Biomechanics
https://www.readbyqxmd.com/read/28507191/lowering-metabolic-rate-mitigates-muscle-atrophy-in-western-fence-lizards
#9
J Balaban, E Azizi
Extended periods of skeletal muscle disuse can cause a significant loss of contractile proteins, which compromises the ability to generate force, mechanical work or power, thus compromising locomotor performance. Several hibernating organisms can resist muscle atrophy despite months of inactivity. This resistance has been attributed to a reduction in body temperature and metabolic rate and activation of physiological pathways that counteract pathways of protein degradation. However, in these systems such strategies are not mutually exclusive and the effects of these mechanisms can be difficult to separate...
May 15, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28501023/force-velocity-relationship-of-leg-muscles-assessed-with-motorized-treadmill-tests-two-velocity-method
#10
Slobodanka Dobrijevic, Vladimir Ilic, Sasa Djuric, Slobodan Jaric
Linear regression models applied on force (F) and velocity (V) data obtained from loaded multi-joint functional movement tasks have often been used to assess mechanical capacities of the tested muscles. The present study aimed to explore the properties of the F-V relationship of leg muscles exerting the maximum pulling F at a wide range of V on a standard motorized treadmill. Young and physically active male and female subjects (N=13+15) were tested on their maximum pulling F exerted horizontally while walking or running on a treadmill set to 8 different velocities (1...
July 2017: Gait & Posture
https://www.readbyqxmd.com/read/28475551/evaluation-of-muscle-mechanical-capacities-through-the-two-load-method-optimization-of-the-load-selection
#11
Alejandro Pérez-Castilla, Slobodan Jaric, Belén Feriche, Paulino Padial, Amador García-Ramos
Recent research has revealed that the force-velocity relationship obtained from the 'two-load method' (i.e., functional movements tested against just 2 external loads) could be a feasible method for the selective assessment of muscle force, velocity, and power-producing capacities. The study investigated the reliability and concurrent validity of the outcomes of the two-load method observed from (1) farther vs. closer data points (20-70%1RM, 30-60%1RM, and 40-50%1RM), and (2) force-biased (50-70%1RM) vs. velocity-biased (20-40%1RM) data points...
April 25, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28469742/muscle-force-velocity-relationships-observed-in-four-different-functional-tests
#12
Milena Z Zivkovic, Sasa Djuric, Ivan Cuk, Dejan Suzovic, Slobodan Jaric
The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force-velocity relationship modeling...
February 2017: Journal of Human Kinetics
https://www.readbyqxmd.com/read/28462115/therapeutic-potential-of-eccentric-exercises-for-age-related-muscle-atrophy
#13
REVIEW
Jae-Young Lim
Recent studies have focused on evidence-based interventions to prevent mobility decline and enhance physical performance in older adults. Several modalities, in addition to traditional strengthening programs, have been designed to manage age-related functional decline more effectively. In this study, we reviewed the current relevant literatures to assess the therapeutic potential of eccentric exercises for age-related muscle atrophy (sarcopenia). Age-related changes in human skeletal muscle, and their relationship with physical performance, are discussed with reference to in vitro physiologic and human biomechanics studies...
September 2016: Integr Med Res
https://www.readbyqxmd.com/read/28338423/assessment-of-leg-muscles-mechanical-capacities-which-jump-loading-and-variable-type-provide-the-most-reliable-outcomes
#14
Amador García-Ramos, Belén Feriche, Alejandro Pérez-Castilla, Paulino Padial, Slobodan Jaric
This study aimed to explore the strength of the force-velocity (F-V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F0], slope [a], maximum velocity [V0], and maximum power [P0]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75 kg loads. The maximum and averaged values of F and V were obtained for the F-V relationship modelling...
July 2017: European Journal of Sport Science
https://www.readbyqxmd.com/read/28328719/predicting-the-maximum-dynamic-strength-in-bench-press-the-high-precision-of-the-bar-velocity-approach
#15
Irineu Loturco, Ronaldo Kobal, José E Moraes, Katia Kitamura, César C Cal Abad, Lucas A Pereira, Fábio Y Nakamura
Loturco, I, Kobal, R, Moraes, JE, Kitamura, K, Cal Abad, CC, Pereira, LA, and Nakamura, FY. Predicting the maximum dynamic strength in bench press: the high precision of the bar velocity approach. J Strength Cond Res 31(4): 1127-1131, 2017-The aim of this study was to determine the force-velocity relationship and test the possibility of determining the 1 repetition maximum (1RM) in "free weight" and Smith machine bench presses. Thirty-six male top-level athletes from 3 different sports were submitted to a standardized 1RM bench press assessment (free weight or Smith machine, in randomized order), following standard procedures encompassing lifts performed at 40-100% of 1RM...
April 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28282405/in-vivo-muscle-force-and-muscle-power-during-near-maximal-frog-jumps
#16
Eng Kuan Moo, Daniel R Peterson, Timothy R Leonard, Motoshi Kaya, Walter Herzog
Frogs' outstanding jumping ability has been associated with a high power output from the leg extensor muscles. Two main theories have emerged to explain the high power output of the frog leg extensor muscles, either (i) the contractile conditions of all leg extensor muscles are optimized in terms of muscle length and speed of shortening, or (ii) maximal power is achieved through a dynamic catch mechanism that uncouples fibre shortening from the corresponding muscle-tendon unit shortening. As in vivo instantaneous power generation in frog hind limb muscles during jumping has never been measured directly, it is hard to distinguish between the two theories...
2017: PloS One
https://www.readbyqxmd.com/read/28253041/load-force-and-power-velocity-relationships-in-the-prone-pull-up-exercise
#17
Mario Muñoz-López, David Marchante, Miguel A Cano-Ruiz, José López Chicharro, Carlos Balsalobre-Fernández
PURPOSE: To analyze the load, force and power-velocity relationships, as well as to determine the load that optimizes power output on the pull-up exercise. METHODS: Eighty-two resistance trained males (Age = 26.8 ± 5.0 yrs.; Pull-up 1RM - normalized per kg of body mass- = 1.5 ± 0.34) performed two repetitions with 4 incremental loads (ranging 70-100%1-RM) in the pull-up exercise while mean propulsive velocity (MPV), force (MPF) and power (MPP) were measured using a linear transducer...
March 2, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28245549/a-rls-svm-aided-fusion-methodology-for-ins-during-gps-outages
#18
Yiqing Yao, Xiaosu Xu
In order to maintain a relatively high accuracy of navigation performance during global positioning system (GPS) outages, a novel robust least squares support vector machine (LS-SVM)-aided fusion methodology is explored to provide the pseudo-GPS position information for the inertial navigation system (INS). The relationship between the yaw, specific force, velocity, and the position increment is modeled. Rather than share the same weight in the traditional LS-SVM, the proposed algorithm allocates various weights for different data, which makes the system immune to the outliers...
February 24, 2017: Sensors
https://www.readbyqxmd.com/read/28223172/a-simple-model-of-cardiac-muscle-for-multiscale-simulation-passive-mechanics-crossbridge-kinetics-and-calcium-regulation
#19
Fyodor A Syomin, Andrey K Tsaturyan
A simple model of cardiac muscle was designed for multiscale simulation of heart mechanics. Relaxed cardiac muscle was described as a transversally isotropic hyperelastic material. Active tension caused by actin-myosin crossbridges depends on the ensemble averaged strain of myosin heads bound to actin. Calcium activation was modeled by Ca(2+) binding to troponin-C. To account for the dependence of troponin affinity for Ca(2+) on myosin heads strongly bound to actin, the kinetics of troponin binding to Ca(2+) in the overlap zone of the thin and thick filaments and outside it were separated...
February 20, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/28202584/comparison-of-human-gastrocnemius-forces-predicted-by-hill-type-muscle-models-and-estimated-from-ultrasound-images
#20
Taylor J M Dick, Andrew A Biewener, James M Wakeling
Hill-type models are ubiquitous in the field of biomechanics, providing estimates of a muscle's force as a function of its activation state and its assumed force-length and force-velocity properties. However, despite their routine use, the accuracy with which Hill-type models predict the forces generated by muscles during submaximal, dynamic tasks remains largely unknown. This study compared human gastrocnemius forces predicted by Hill-type models with the forces estimated from ultrasound-based measures of tendon length changes and stiffness during cycling, over a range of loads and cadences...
May 1, 2017: Journal of Experimental Biology
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