Mechanism Of Force Production Research Articles

The impact of general and/or specific warm-up on power and velocity during squat and bench-press training

The study aimed to compare the effects of two warm-up strategies on mechanical force production during bench press and squat resistance training sessions. Twenty-six trained male subjects (24.37±5.83years, 75.48±12.12kg, 1.74±0.07m) performed a squat or bench press resistance training session after a specific warm-up (SWU) or general warm-up followed by a specific warm-up (GSWU). The SWU included 2x6 repetitions at 32% and 64% of the maximal load (1RM), respectively. The GSWU included 10 minutes of treadmill running (70% of heart rate reserve) followed by SWU. The resistance training session consisted of 3x6 with a load of 80% 1RM. Mechanical (mean propulsive velocity, mean propulsive power and velocity loss), physiological [heart rate (HR), blood lactate concentration], and psychophysiological variables (rating of perceived exertion) were evaluated. In the bench press and squat resistance training sessions, no differences were found in the mechanical and psychophysiological variables. When performing the bench press, the GSWU caused an increased HR response after warm-up (100.00±16.93bpm vs. 110.57±9.69bpm, p=0.03; ES=0.65, moderate effect). GSWU or SWU can both be used as preparatory activities for bench press and squat resistance training performance without related restrictions. These findings may be helpful for professionals to provide appropriate warm-up strategies to maximize resistance training. Keywords: Pre-exercise, Strength, T-Force, Velocity, Physiology, Resistance Training

A low-cost 2-D sarcomere model to demonstrate titin-related mechanisms for force production.

Given the recently proposed three-filament theory of muscle contraction, we present a low-cost physical sarcomere model aimed at illustrating the role of titin in the production of active force in skeletal muscle. With inexpensive materials, it is possible to illustrate actin-myosin cross-bridge interactions between the thick and thin filaments and demonstrate the two different mechanisms by which titin is thought to contribute to active and passive muscle force. Specifically, the model illustrates how titin, a molecule with springlike properties, may increase its stiffness by binding free calcium upon muscle activation and reducing its extensible length by attaching itself to actin, resulting in the greater force-generating capacity after an active than a passive elongation that has been observed experimentally. The model is simple to build and manipulate, and demonstration to high school students was shown to result in positive perception and improved understanding of the otherwise complex titin-related mechanisms of force production in skeletal and cardiac muscles.NEW & NOTEWORTHY Our physical sarcomere model illustrates not only the classic view of muscle contraction, the sliding filament and cross-bridge theories, but also the newly discovered role of titin in force regulation, called the three-filament theory. The model allows for easy visualization of the role of titin in muscle contraction and aids in explaining complex muscle properties that are not captured by the traditional cross-bridge theory.

Analysis of Stator-Slot and Pole-Pair Combinations in a Two-Degree-of-Freedom Split-Stator Induction Machine Based on Motion Coupling Model

2-degree-of-freedom split-stator induction machine (2DoFSSIM) exhibits high integration and material utilization for 2DoF motions, but the attractive topologies are difficult to determine due to exciting two different magnetic fields and two-directional motions. This paper investigates the helical motion coupling effect of rotary and linear motion parts, then the influence of stator-slot and pole-pair combinations on three motion characteristics is analyzed. Based on the proposed motion coupling model, the resistant torque and force production mechanism is revealed. It can be concluded that the output torque, force, and helical motion coupling effect are dominantly determined by the magnetic loading and pole-pair number of two motion parts. However, there is a tradeoff in choosing the pole-pair number to get the 2DoFSSIMs with high output performances and low helical motion coupling effect. Then, the stator-slot and pole-pair combinations selection method is proposed, and the topologies with attractive performances are chosen at different geometric diameters. Finally, the finite element analysis and experimental results are given to validate the proposed technique. <list list-type="simple" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <list-item> 2-degree-of-freedom split-stator induction machine, motion coupling model, helical motion. </list-item> </list>

Measuring and modeling forces generated by microtubules.

Tubulins are essential proteins, which are conserved across all eukaryotic species. They polymerize to form microtubules, cytoskeletal components of paramount importance for cellular mechanics. The microtubules combine an extraordinarily high flexural rigidity and a non-equilibrium behavior, manifested in their intermittent assembly and disassembly. These chemically fueled dynamics allow microtubules to generate significant pushing and pulling forces at their ends to reposition intracellular organelles, remodel membranes, bear compressive forces, and transport chromosomes during cell division. In this article, we review classical and recent studies, which have allowed the quantification of microtubule-generated forces. The measurements, to which we owe most of the quantitative information about microtubule forces, were carried out in biochemically reconstituted systems in vitro. We also discuss how mathematical and computational modeling has contributed to the interpretations of these results and shaped our understanding of the mechanisms of force production by tubulin polymerization and depolymerization.

A new crystal structure of a kinesin mutant with greater mechanical output than wild type—identification of a structural element involved in force production

The kinesin-14 Ncd microtubule motor protein plays a central role in division in Drosophila oocytes and early embryos. The motor binds to microtubules and hydrolyzes ATP to produce force and slide microtubules during spindle assembly. The force production mechanism is thought to involve coupling of ATP hydrolysis to small conformational changes in the motor domain that store and release energy, and are amplified by the large rotation of the coiled-coil stalk. However, these changes have not been fully identified.

Unsteady aerodynamics of a model bristled wing in rapid acceleration motion

Tiny insects with bristled wings perform the “rowing” motion: the wings accelerate rapidly from zero-velocity to certain reference velocity at 90° angle-of-attack, and the drag produced in this motion provides the weight-supporting force. A flat-plate wing will produce a large drag in such a motion, but it is unknown whether a bristled wing could do so. Here, we study this problem using numerical simulation and simple model wings. The acceleration is large: the wing translates only about half the wing chord length to reach the reference velocity. The following is shown. The bristled wing can produce a very large unsteady drag peak and large time-averaged drag as a flat-plate wing does; the time-averaged drag is about 2.5 times as large as the quasi-steady value. The force production mechanisms are different between the two wings: for the flat-plate wing, because of the large acceleration, the added-mass and the strong free vorticity in the flow produce a large pressure difference between the windward and leeward surfaces of the plate, resulting in large drag (surface frictional force has negligible contribution). Yet for the bristled wing, although the acceleration of the wing is large, a bristle needs to translate about 80 diameters to reach the reference velocity; thus, the effect of acceleration is very weak. Each bristle operates in a quasi-steady Stokes flow and the large drag of the bristled wing is due to the very large surface pressure and frictional forces on each bristle, generated by the strong viscous effect of the Stokes flow (the drag is equally contributed by the surface pressure and frictional forces).

Flight among the Lilliputians

If you think that fruit flies are tiny, please reconsider. Spectacular radiations of miniaturized beetles, flies and wasps dominate the insect fauna and are characterized by body lengths well below that of the biologist's friend Drosophila melanogaster (∼3 mm). Most remarkably, the smallest flying insect described to date has a length of just 0.16 mm. But just how does flapping flight work at such small scales? The viscous effects of air on a wing increase at smaller sizes and a 1 mm insect moves through the air as would a bumblebee move through mineral oil. Lift forces generated by swirling air around the wing are accordingly impeded given the relative stickiness of the fluid, and alternative mechanisms of force production must be at play. How then do very small insects create the aerodynamic forces necessary to offset body weight and also to generate horizontal thrust to intentionally move about?Xin Cheng and Mao Sun, from Beihang University, China, took on this question by describing the detailed kinematics of forward flight in the tiny wasp Encarsia formosa, which has a wing length of only 0.5 mm. Writing in 1973 in JEB, Torkel Weis-Fogh first described the novel clap-fling aerodynamic mechanism utilized by this species; Cheng and Sun have now built on their earlier computational work on hovering in E. formosa to analyze its forward flight kinematics and associated forces, albeit at the humble airspeed of ∼0.3 m s−1. They identified a distinctive pattern of wing motions very different from that of larger insects (including the fruit fly). First, the wings accelerate backward at very high incidence angles relative to oncoming flow (‘impulsive paddling’), and then close up on the right and left sides while at the same time moving upward. Then in the downstroke, the wings quickly rotate about their posterior edges (which Weis-Fogh referred to as the ‘fling’) and sweep downward and forward, again moving at high incidence angles to the surrounding air.But what do these odd features of wing flapping yield in terms of force production? Cheng and Sun used computer simulations to reveal two means by which the effects of small size and fluid stickiness were largely overcome. Firstly, the fast backward acceleration of the wings at high incidence to the air produces a large thrust but also some vertical force supporting the body weight. Secondly, the ‘flinging’ motion produces a low-pressure region of rapidly swirling air which persists through the downstroke, creating the majority of the vertical force required to offset gravity. Thus, the insects employ distinctive wing motions to offset the otherwise formidable effects of increased viscosity. The associated forces last just milliseconds but, at a wingbeat frequency of ∼350 Hz, are clearly sufficient for routine flight. They may be even more effective during maneuvers, a topic destined for future investigation.Miniaturization is one of the dominant themes in insect evolution and largely underpins the high extant diversity of small insects (and also of their parasitoids). This computational study of aerodynamics in one such lilliputian species suggests that additional fluid dynamic novelties await discovery and analysis by flight biomechanists. Fringed wings with much reduced supporting veins are also well known among the miniaturized fliers, but have largely unknown aerodynamic consequences. Often at the mercy of gentle breezes, these insects live in physical, behavioral and ecological domains supremely distant from our own personal experiences. This aerodynamic study should help us to close that conceptual distance.

Introduction to the Symposium: Bio-Inspiration of Quiet Flight of Owls and Other Flying Animals: Recent Advances and Unanswered Questions.

Animal wings produce an acoustic signature in flight. Many owls are able to suppress this noise to fly quietly relative to other birds. Instead of silent flight, certain birds have conversely evolved to produce extra sound with their wings for communication. The papers in this symposium synthesize ongoing research in "animal aeroacoustics": the study of how animal flight produces an acoustic signature, its biological context, and possible bio-inspired engineering applications. Three papers present research on flycatchers and doves, highlighting work that continues to uncover new physical mechanisms by which bird wings can make communication sounds. Quiet flight evolves in the context of a predator-prey interaction, either to help predators such as owls hear its prey better, or to prevent the prey from hearing the approaching predator. Two papers present work on hearing in owls and insect prey. Additional papers focus on the sounds produced by wings during flight, and on the fluid mechanics of force production by flapping wings. For instance, there is evidence that birds such as nightbirds, hawks, or falcons may also have quiet flight. Bat flight appears to be quieter than bird flight, for reasons that are not fully explored. Several research avenues remain open, including the role of flapping versus gliding flight or the physical acoustic mechanisms by which flight sounds are reduced. The convergent interest of the biology and engineering communities on quiet owl flight comes at a time of nascent developments in the energy and transportation sectors, where noise and its perception are formidable obstacles.

Improving Mechanical Effectiveness During Sprint Acceleration: Practical Recommendations and Guidelines

ABSTRACT Sport scientists and strength and conditioning coaches are showing growing interest in the magnitude, orientation, and application of ground reaction force during acceleration actions in sport, as it can identify the key mechanical determinants of performance. Horizontal force-velocity profiling or sprint profiling helps practitioners understand the capacity of the mechanical force production during the acceleration phase of a sprint. This review examines the methods used in the field for determining horizontal force-velocity (sprint) profiles. It also includes recommendations for practical training methods to address individual force-velocity characteristics, mechanical effectiveness, thereby optimizing acceleration performance.

Mechanical Function of the Nucleus in Force Generation during Epithelial Morphogenesis

SummaryMechanical forces are critical regulators of cell shape changes and developmental morphogenetic processes. Forces generated along the epithelium apico-basal cell axis have recently emerged as essential for tissue remodeling in three dimensions. Yet the cellular machinery underlying those orthogonal forces remains poorly described. We found that during Drosophila leg folding cells eventually committed to die produce apico-basal forces through the formation of a dynamic actomyosin contractile tether connecting the apical surface to a basally relocalized nucleus. We show that the nucleus is anchored to basal adhesions by a basal F-actin network and constitutes an essential component of the force-producing machinery. Finally, we demonstrate force transmission to the apical surface and the basal nucleus by laser ablation. Thus, this work reveals that the nucleus, in addition to its role in genome protection, actively participates in mechanical force production and connects the contractile actomyosin cytoskeleton to basal adhesions.

A New Double-Sided Linear Flux-Switching Permanent Magnet Motor With Yokeless Mover for Electromagnetic Launch System

A new double-sided linear flux-switching permanent magnet (DSLFSPM) motor with a yokeless mover is proposed in this paper. First, the topology and structure of the proposed motor are presented, and the pole pitch ratio and segment number are shown to strongly affect performance. Second, the electromagnetic performance of DSLFSPM motors with a secondary yoke and without a secondary yoke are compared and described. Third, according to analytical models, air-gap flux-density levels and corresponding harmonics are investigated, and force production mechanisms of the proposed motor are presented. The analytical results match to the FEA results. Finally, experiments on a prototype are carried out to validate the simulation results. Back EMF, cogging force, and inductance values of the prototypes are measured and experimental results for the drive systems are presented.

Passive muscle tension increases in proportion to intramuscular fluid volume.

During extended bouts of exercise, muscle can increase in volume by as much as 20% as vascular fluid moves into the tissue. Recent findings suggest that the fluid content of muscle can influence the mechanics of force production; however, the extent to which natural volume fluctuations should be expected to influence muscle mechanics in vivo remains unclear. Here, using osmotic perturbations of bullfrog muscle, we explored the impacts of physiologically relevant volume fluctuations on a fundamental property of muscle: passive force production. We found that passive force and fluid volume were correlated over a 20% increase in muscle volume, with small changes in volume having significant effects on force (e.g. a 5% volume increase results in a >10% passive force increase). A simple physical model of muscle morphology reproduces these effects. These findings suggest that physiologically relevant fluid fluxes could alter passive muscle mechanics in vivo and affect organismal performance.

Architectural and functional specifics of the human triceps surae muscle in vivo and its adaptation to microgravity.

Long-term exposure to microgravity (μG) is known to reduce the strength of a skeletal muscle contraction and the level of general physical performance in humans, while little is known about its effect on muscle architecture. Architectural and contractile properties of the triceps surae (TS) muscle were determined in vivo for male cosmonauts in response ( n = 8) to a spaceflight (213.0 ± 30.5 days). The maximal voluntary contraction (MVC), tetanic tension ( Ро), and voluntary and electrically evoked contraction times and force deficiency (Pd) were determined. The ankle was positioned at 15° dorsiflexion (-15°) and 0, 15, and 30° plantar flexion, with the knee set at 90°. At each position, longitudinal ultrasonic images of the medial (MG) and lateral (LG) gastrocnemius and soleus (SOL) muscles were obtained while the subject was relaxed. After a spaceflight, MVC and Pо decreased by 42 and 26%, respectively, and Pd increased by 50%. The rate of tension of a voluntary contraction substantially reduced but evoked contractions remained unchanged. In the passive condition, fiber length ( Lf) changed from 43, 57, and 35 mm (knee, 0°; ankle, -15°) to 34, 38, and 25 mm (knee, 0°; ankle, 30°) for MG, LG, and SOL, respectively, and Θf changed from 27, 21, and 23° (knee, 0°; ankle, -15°) to 43, 29, and 34° (knee, 0°; ankle, 30°) for MG, LG, and SOL, respectively. Different Lf and Θf, and their changes after spaceflight, might be related to differences in force-producing capabilities of the muscles and elastic characteristics of tendons and aponeuroses. NEW & NOTEWORTHY The present work was the first to combine measuring the fiber length and pennation angle (ultrasound imaging) as main determinants of mechanical force production and evaluating the muscle function after a long-duration spaceflight. The results demonstrate that muscles with different functional roles may differently respond to unloading, and this circumstance is important to consider when planning rehabilitation after unloading of any kind, paying particular attention to postural muscles.

Investigation and Analysis of Force Production Mechanism for Partitioned Stator Flux Reversal Permanent Magnet Linear Machine

Investigation and Analysis of Force Production Mechanism for Partitioned Stator Flux Reversal Permanent Magnet Linear Machine

Molecular mechanisms of force production in clathrin-mediated endocytosis.

During clathrin-mediated endocytosis (CME), a flat patch of membrane is invaginated and pinched off to release a vesicle into the cytoplasm. In yeast CME, over 60 proteins-including a dynamic actin meshwork-self-assemble to deform the plasma membrane. Several models have been proposed for how actin and other molecules produce the forces necessary to overcome the mechanical barriers of membrane tension and turgor pressure, but the precise mechanisms and a full picture of their interplay are still not clear. In this review, we discuss the evidence for these force production models from a quantitative perspective and propose future directions for experimental and theoretical work that could clarify their various contributions.

A study on propelling force production mechanism under the motor shaft direct drive scheme (Generation of forward motion on single motor shaft direct drive vehicle)

A study on propelling force production mechanism under the motor shaft direct drive scheme (Generation of forward motion on single motor shaft direct drive vehicle)

Design and comparison of two kinds of primary wound field flux-switching linear motors

PurposeThe purpose of this paper is to propose the complementary design rules, give a quantitative comparison and analyze the force production mechanism of two kinds of primary wound field flux-switching linear (PWFFSL) motors.Design/methodology/approachPWFFSL motors have the merits of no use of rare-earth magnet, low cost and a wide operation range in which the armature windings and the field windings are all located at the short primary mover and the secondary is very robust. Hence, the PWFFSL motor is ideal for rail transportation systems which need a long stator and a wide speed range. To overcome the disadvantages of the existing PWFFSL motors, new complementary design rules will be proposed. Also, to offer a better PWFFSL motor for the rail transportation systems, it is necessary to investigate different structures of PWFFSL motors and give a comprehensive comparison. To predict the force performance of two kinds of PWFFSL motors with different secondary types, their flux density analysis and force production mechanism will be presented and compared.FindingsThe comparison result shows that the PWFFSL motor with toothed secondary can offer larger thrust force, higher force density and higher efficiency, whereas the PWFFSL motor with segmented secondary has the merits of lower force ripple, less use of stator iron, higher power factor and less critical saturation.Research limitations/implicationsMany PWFFSL motors with different primary/secondary pole pitches based on the proposed design principle have not been considered in this paper.Originality/valueThis paper has presented the air-gap flux analysis, proposed the complementary design rules for two kinds of PWFFSL motors with different secondary types and compared the electromagnetic performance of the two motors.

Force and Directional Force Modulation Effects on Accuracy and Variability in Low-Level Pinch Force Tracking

ABSTRACTThe authors investigated how varying the required low-level forces and the direction of force change affect accuracy and variability of force production in a cyclic isometric pinch force tracking task. Eighteen healthy right-handed adult volunteers performed the tracking task over 3 different force ranges. Root mean square error and coefficient of variation were higher at lower force levels and during minimum reversals compared with maximum reversals. Overall, the thumb showed greater root mean square error and coefficient of variation scores than did the index finger during maximum reversals, but not during minimum reversals. The observed impaired performance during minimum reversals might originate from history-dependent mechanisms of force production and highly coupled 2-digit performance.

Microscale In-Plane Knudsen Radiometric Actuator: Design, Characterization, and Performance Modeling

Thermally driven gas flow is exploited in a microscale device for the purpose of gas pressure dependent actuation in rarefied environments. The device relies on the in-plane motion of a shuttle mass in response to Knudsen thermal forces. The shuttle response is measured capacitively and the magnitude is used to estimate ambient pressure. Combined with heating element resistance, these measurements, in principle, enable the simultaneous determination of gas composition if the constituents are known. Numerical simulations using direct simulation Monte Carlo are carried out to elucidate the mechanisms of force production. Results reveal highly vortical flow structures forming high pressure regions at the shuttle surface. The experimental and numerical results are expressed in terms of a non-dimensional Knudsen force coefficient, allowing force magnitude to be estimated for dynamically similar geometries.

YAP is essential for mechanical force production and epithelial cell proliferation during lung branching morphogenesis.

Branching morphogenesis is a fundamental program for tissue patterning. We show that active YAP, a key mediator of Hippo signaling, is distributed throughout the murine lung epithelium and loss of epithelial YAP severely disrupts branching. Failure to branch is restricted to regions where YAP activity is removed. This suggests that YAP controls local epithelial cell properties. In support of this model, mechanical force production is compromised and cell proliferation is reduced in Yap mutant lungs. We propose that defective force generation and insufficient epithelial cell number underlie the branching defects. Through genomic analysis, we also uncovered a feedback control of pMLC levels, which is critical for mechanical force production, likely through the direct induction of multiple regulators by YAP. Our work provides a molecular pathway that could control epithelial cell properties required for proper morphogenetic movement and pattern formation.