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https://www.readbyqxmd.com/read/28901373/kinesin-and-dynein-mechanics-measurement-methods-and-research-applications
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
https://www.readbyqxmd.com/read/28860175/skeletal-muscle-contractile-properties-in-a-novel-murine-model-for-limb-girdle-muscular-dystrophy-2i
#7
Jordan D Rehwaldt, Buel D Rodgers, David C Lin
Limb-girdle muscular dystrophy (LGMD) 2i results from mutations in fukutin-related protein and aberrant α-dystroglycan glycosylation. Although this significantly compromises muscle function and ambulation, the comprehensive characteristics of contractile dysfunction are unknown. We therefore quantified the in situ contractile properties of the medial gastrocnemius in young adult P448L mice, an affected muscle and novel model of LGMD2i, respectively. Maximal twitch force, tetanic force and power normalized to physiological cross-sectional area were significantly smaller in P448L mice, compared to sex-matched wild-type mice...
August 31, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/28828076/effects-of-cluster-sets-and-rest-redistribution-on-mechanical-responses-to-back-squats-in-trained-men
#8
James J Tufano, Jenny A Conlon, Sophia Nimphius, Lee E Brown, Alex Petkovic, Justin Frick, G Gregory Haff
Eight resistance-trained men completed three protocols separated by 48-96 hours. Each protocol included 36 repetitions with the same rest duration, but the frequency and length of rest periods differed. The cluster sets of four (CS4) protocol included 30 s of rest after the 4th, 8th, 16th, 20th, 28th, and 32nd repetition in addition to 120 s of rest after the 12th and 24th repetition. For the other two protocols, the total 420 s rest time of CS4 was redistributed to include nine sets of four repetitions (RR4) with 52...
September 2017: Journal of Human Kinetics
https://www.readbyqxmd.com/read/28768340/a-novel-two-velocity-method-for-elaborate-isokinetic-testing-of-knee-extensors
#9
Vladimir Grbic, Sasa Djuric, Olivera M Knezevic, Dragan M Mirkov, Aleksandar Nedeljkovic, Slobodan Jaric
Single outcomes of standard isokinetic dynamometry tests do not discern between various muscle mechanical capacities. In this study, we aimed to (1) evaluate the shape and strength of the force-velocity relationship of knee extensors, as observed in isokinetic tests conducted at a wide range of angular velocities, and (2) explore the concurrent validity of a simple 2-velocity method. Thirteen physically active females were tested for both the peak and averaged knee extensor concentric force exerted at the angular velocities of 30°-240°/s recorded in the 90°-170° range of knee extension...
September 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28758518/allometric-scaling-of-power-force-velocity-ergometry-profiles-in-men
#10
Hamdi Jaafar
AIM: To examine the appropriate magnitude of allometric scaling of the force-velocity relationship according to body dimensions and to establish normative data for the power-force-velocity relationship for active men. SUBJECTS AND METHODS: Ninety-seven participants completed a force-velocity test on a Monark cycle ergometer. Allometric exponents and percentile ranks were established for maximal power (Pmax), maximal force (F0) and maximal velocity (V0). RESULTS: The mean (± SD) of Pmax, F0 and V0 were 1114...
July 31, 2017: Annals of Human Biology
https://www.readbyqxmd.com/read/28752950/cell-protrusion-and-retraction-driven-by-fluctuations-in-actin-polymerization-a-two-dimensional-model
#11
Gillian L Ryan, Danielle Holz, Sawako Yamashiro, Daisuke Taniguchi, Naoki Watanabe, Dimitrios Vavylonis
Animal cells that spread onto a surface often rely on actin-rich lamellipodial extensions to execute protrusion. Many cell types recently adhered on a two-dimensional substrate exhibit protrusion and retraction of their lamellipodia, even though the cell is not translating. Travelling waves of protrusion have also been observed, similar to those observed in crawling cells. These regular patterns of protrusion and retraction allow quantitative analysis for comparison to mathematical models. The periodic fluctuations in leading edge position of XTC cells have been linked to excitable actin dynamics using a one-dimensional model of actin dynamics, as a function of arc-length along the cell...
July 28, 2017: Cytoskeleton
https://www.readbyqxmd.com/read/28685862/sprint-mechanics-evaluation-using-inertial-sensor-based-technology-a-laboratory-validation-study
#12
Igor Setuain, Pablo Lecumberri, Juha P Ahtiainen, Antti A Mero, Keijo Häkkinen, Mikel Izquierdo
Advances in micro-electromechanical systems have turned magnetic inertial measurement units (MIMUs) into a suitable tool for vertical jumping biomechanical evaluation. Thus, the presented study aimed to determine if appropriate reliability and agreement reports could also be obtained when analysing 20m sprint mechanics. Four bouts of 20 m sprints were evaluated to determine if the data provided by a MIMU placed at the lumbar spine could reliably assess sprint mechanics and to examine the validity of the MIMU sensor compared to force plate recordings...
July 7, 2017: Scandinavian Journal of Medicine & Science in Sports
https://www.readbyqxmd.com/read/28678768/effects-of-lower-limb-strength-training-on-agility-repeated-sprinting-with-changes-of-direction-leg-peak-power-and-neuromuscular-adaptations-of-soccer-players
#13
Mehréz Hammami, Yassine Negra, François Billaut, Souhail Hermassi, Roy J Shephard, Mohamed Souhaiel Chelly
We examined the effects on explosive muscular performance of incorporating 8 weeks strength training into the preparation of junior male soccer players, allocating subjects between an experimental group (E, n=19) and a matched control group (C, n=12). Controls maintained their regular training program, but the experimental group replaced a part of this schedule by strength training. Performance was assessed using running times (5m, 10m, 20m, 30 and 40m), a sprint test with 180° turns (S180°), a 9-3-6-3-9 m sprint with backward and forward running (SBF), a 4 x 5 m sprint test with turns, repeated shuttle sprinting, repeated changes of direction, squat (SJ) and counter-movement (CMJ) jumping, back half-squatting, and a force-velocity test...
January 24, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28657791/selective-changes-on-the-mechanical-capacities-of-lower-body-muscles-after-a-cycle-ergometer-sprint-training-against-heavy-and-light-resistances
#14
Amador García-Ramos, Alejandro Torrejón, Alejandro Pérez-Castilla, Antonio J Morales-Artacho, Slobodan Jaric
PURPOSE: This study explored the feasibility of the linear force-velocity (F-V) modelling approach to detect selective changes of the F-V parameters (i.e., maximum force [F0], maximum velocity [V0], F-V slope [a], and maximum power [P0]) following a sprint training program. METHODS: Twenty-seven men were randomly assigned to a heavy load group (HLG), light load group (LLG), or control group (CG). The training sessions (6 weeks × 2 sessions per week) comprised performing eight maximal effort sprints against either heavy (HLG) or light (LLG) resistances in the leg cycle ergometer exercise...
June 28, 2017: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/28639444/comparison-of-shuttle-and-straight-repeated-sprint-ability-tests-and-their-relationship-to-anthropometrics-and-explosive-muscular-performance-of-lower-limb-in-elite-handball-players
#15
Souhail Hermassi, René Schwesig, Rainer Wollny, Georg Fieseler, Roland van den Tillaar, Jaime Fernandez-Fernandez, Roy J Shephard, Mohamed S Chelly
BACKGROUND: This study assessed inter-relationships between shuttle and straight repeated-sprint ability tests and the relationship of each measure to anthropometric and explosive lower limb performance data in elite handball players. METHODS: Twenty-two elite male handball players (18.9 ± 0.2 years; body mass: 83.3 ± 1.1 kg, height: 1.79 ± 2.30 m, body fat: 12.8 ± 0.2%) completed tests that included a lower limb force-velocity test of peak power (Wpeak), jumping ability (squat and counter-movement jumps; SJ, CMJ), 1 repetition maximum (1-RM) half back squat, average sprint velocity over 5 m (V-5 m), peak velocity between 25-30 m (Vmax), and Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1), and anthropometric determinations of cross-sectional areas and muscle volumes for leg and thigh muscles...
June 21, 2017: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/28632047/reliability-and-magnitude-of-mechanical-variables-assessed-from-unconstrained-and-constrained-loaded-countermovement-jumps
#16
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...
November 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28605252/a-simple-method-for-assessing-upper-limb-force-velocity-profile-in-bench-press
#17
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
#18
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
#19
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
#20
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
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