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1
Eng, Carolyn M., et Thomas J. Roberts. « Aponeurosis influences the relationship between muscle gearing and force ». Journal of Applied Physiology 125, no 2 (1 août 2018) : 513–19. http://dx.doi.org/10.1152/japplphysiol.00151.2018.
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Aponeuroses are connective tissues found on the surface of pennate muscles and are in close association with muscle fascicles. In addition to transmitting muscle forces to the external tendon, aponeurosis has been hypothesized to influence the direction of muscle shape change during a contraction. Muscle shape changes affect muscle contractile force and velocity because they influence the gear ratio with which muscle fascicles transmit force and velocity to the tendon. If aponeurosis modulates muscle shape changes, altering the aponeurosis’ radial integrity with incisions should alter gearing. We tested the hypothesis that incising the aponeurosis would lead to decreased gearing across force conditions with an in situ preparation of the turkey lateral gastrocnemius muscle. We found that multiple full-length incisions in the aponeurosis altered the relationship between gearing and force relative to the intact aponeurosis condition. Specifically, after multiple aponeurosis incisions, gear ratio decreased by 19% in the high-force contractions compared with the intact condition. These results suggest that aponeuroses influence muscle shape change and can alter muscle contractile force and speed through their effect on muscle gearing. NEW & NOTEWORTHY Muscle gearing is determined by muscle shape change during a contraction and varies with the force of contraction. Variable gearing influences muscle force and speed, but how gearing is modulated is not well understood. Incising the aponeurosis before and after contractions demonstrates that aponeurosis plays a role in modulating gearing.
2
Carrier, D. R., C. S. Gregersen et N. A. Silverton. « Dynamic gearing in running dogs ». Journal of Experimental Biology 201, no 23 (1 décembre 1998) : 3185–95. http://dx.doi.org/10.1242/jeb.201.23.3185.
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Dynamic gearing is a mechanism that has been suggested to enhance the performance of skeletal muscles by maintaining them at the shortening velocities that maximize their power or efficiency. We investigated this hypothesis in three domestic dogs during trotting and galloping. We used ground force recordings and kinematic analysis to calculate the changes in gear ratio that occur during the production of the external work of locomotion. We also monitored length changes of the vastus lateralis muscle, an extensor muscle of the knee, using sonomicrometry in four additional dogs to determine the nature and rate of active shortening of this muscle. During both trotting and galloping, the gear ratios of the extensor muscles of the elbow, wrist and ankle joints were relatively constant early in limb support, but decreased rapidly during the second half of support. The gear ratio at the hip exerted an extensor moment initially, but decreased throughout limb support and became negative midway through support. This pattern of decreasing gear ratio during the second half of support indicates that dynamic gearing does not maximize muscle power or efficiency at the elbow, wrist, hip and ankle joints. In contrast,the extensor muscles of the shoulder and knee joints exhibited an increase in gear ratio during limb support. In two dogs, the vastus lateralis muscle shortened at a relatively constant rate of 3.7-4 lengths s-1 during intermediate-speed galloping. This pattern of increasing gear ratio and constant velocity of muscle shortening at the knee joint is consistent with the hypothesis of dynamic gearing. Given the amount of work done at the knee and shoulder joints of running dogs, dynamic gearing may contribute to the economy of constant-speed running and may be important to integrated limb function.
3
Wakeling, James M., Ollie M. Blake, Iris Wong, Manku Rana et Sabrina S. M. Lee. « Movement mechanics as a determinate of muscle structure, recruitment and coordination ». Philosophical Transactions of the Royal Society B : Biological Sciences 366, no 1570 (27 mai 2011) : 1554–64. http://dx.doi.org/10.1098/rstb.2010.0294.
Texte intégralRésumé :
During muscle contractions, the muscle fascicles may shorten at a rate different from the muscle-tendon unit, and the ratio of these velocities is its gearing. Appropriate gearing allows fascicles to reduce their shortening velocities and allows them to operate at effective shortening velocities across a range of movements. Gearing of the muscle fascicles within the muscle belly is the result of rotations of the fascicles and bulging of the belly. Variable gearing can also occur as a result of tendon length changes that can be caused by changes in the relative timing of muscle activity for different mechanical tasks. Recruitment patterns of slow and fast fibres are crucial for achieving optimal muscle performance, and coordination between muscles is related to whole limb performance. Poor coordination leads to inefficiencies and loss of power, and optimal coordination is required for high power outputs and high mechanical efficiencies from the limb. This paper summarizes key studies in these areas of neuromuscular mechanics and results from studies where we have tested these phenomena on a cycle ergometer are presented to highlight novel insights. The studies show how muscle structure and neural activation interact to generate smooth and effective motion of the body.
4
Wakeling, James M., Meghan Jackman et Ana I. Namburete. « The Effect of External Compression on the Mechanics of Muscle Contraction ». Journal of Applied Biomechanics 29, no 3 (juin 2013) : 360–64. http://dx.doi.org/10.1123/jab.29.3.360.
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The velocity at which a muscle fascicle will shorten, and hence the force that it can develop, depends on its gearing within the muscle belly. Muscle fascicle length depends on both its pennation and the thickness of the muscle. It was expected that external compression would reduce the muscle thickness and pennation and thus cause a reduction to the gearing of the fascicles relative to the muscle belly. Structural properties of the medial gastrocnemius muscle were visualized using B-mode ultrasound in six subjects. Measurements were taken during cyclical isotonic contractions at three different ankle torques and with the application of no, one, or two elastic compression bandages to the lower leg. Ankle torques and angular velocities were unaffected by the external compression. External compression did, however, reduce the muscle thickness and the fascicle pennation and resulted in a decrease in the gearing within the muscle belly. Reductions in gearing would result in an increase in the muscle fascicle shortening velocity that would reduce the force-generating potential of the fascicles. It is suggested that externally applied compression should not be considered a way to enhance muscle performance when based on the structural mechanics.
5
Wakeling, J. M., et I. A. Johnston. « White muscle strain in the common carp and red to white muscle gearing ratios in fish ». Journal of Experimental Biology 202, no 5 (1 mars 1999) : 521–28. http://dx.doi.org/10.1242/jeb.202.5.521.
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White muscle strains were recorded using sonomicrometry techniques for 70 fast-starts in the common carp Cyprinus carpio L. High-speed cine images were recorded simultaneously for 54 of these starts, and muscle strain was calculated independently from the digitized outlines of the fish. Sonomicrometry measurements of superficial muscle strain were not significantly different from the strain as calculated from the theory of simple bending of a homogeneous material: superficial muscle strain thus varied with chordwise distance from the spine. However, white muscle strain across a transverse section of the myotome shows less variation with chordwise position than would be expected from simple bending theory. Muscle strains measured using sonomicrometry thus do not necessarily represent the more uniform strain predicted for the whole section of the fish. White muscle strain can be accurately predicted from the spine curvatures as measured from the cine images if the gearing ratio between the red and white muscle fibres is known. A model for calculating the gearing ratio from the helical muscle fibre geometry was re-evaluated using current data for the kinematics of fast-starting C. carpio. This model predicted a mean gearing ratio of 2.8 for these fast-starts. A quicker, alternative approach to estimating gearing ratio from the position of the centroid of white fibre area is proposed and results in ratios similar to those calculated from the model of helical geometry. White muscle strains in fish can thus be estimated from measurements of spine curvature and muscle distribution alone.
6
Dick, Taylor J. M., et James M. Wakeling. « Shifting gears : dynamic muscle shape changes and force-velocity behavior in the medial gastrocnemius ». Journal of Applied Physiology 123, no 6 (1 décembre 2017) : 1433–42. http://dx.doi.org/10.1152/japplphysiol.01050.2016.
Texte intégralRésumé :
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 fibers 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. To do this, we obtained recordings of MG tendon length, fascicle length, pennation angle, and thickness using B-mode ultrasound and muscle activation using surface electromyography during cycling at a range of cadences and loads. We found that that increases in contractile force were accompanied by reduced bulging in muscle thickness, reduced increases in pennation angle, and faster fascicle shortening. Although the force and velocity of a muscle contraction are inversely related due to the force-velocity effect, this study has shown how dynamic muscle shape changes are influenced by force and not influenced by velocity.NEW & NOTEWORTHY During movement, skeletal muscles contract and bulge in thickness or width. These shape changes play a key role in modulating the performance of skeletal muscle by increasing its range of operating velocities. Yet to date the underlying mechanisms associated with muscle shape change remain largely unexplored. This study identified muscle force, and not velocity, as the mechanistic driving factor to allow for muscle gearing to vary depending on the contractile conditions during human cycling.
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Roberts, Thomas J., Carolyn M. Eng, David A. Sleboda, Natalie C. Holt, Elizabeth L. Brainerd, Kristin K. Stover, Richard L. Marsh et Emanuel Azizi. « The Multi-Scale, Three-Dimensional Nature of Skeletal Muscle Contraction ». Physiology 34, no 6 (1 novembre 2019) : 402–8. http://dx.doi.org/10.1152/physiol.00023.2019.
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Muscle contraction is a three-dimensional process, as anyone who has observed a bulging muscle knows. Recent studies suggest that the three-dimensional nature of muscle contraction influences its mechanical output. Shape changes and radial forces appear to be important across scales of organization. Muscle architectural gearing is an emerging example of this process.
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Eng, Carolyn M., Emanuel Azizi et Thomas J. Roberts. « Structural Determinants of Muscle Gearing During Dynamic Contractions ». Integrative and Comparative Biology 58, no 2 (7 juin 2018) : 207–18. http://dx.doi.org/10.1093/icb/icy054.
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Wang, Yingjie, Chunbao Liu, Luquan Ren et Lei Ren. « Load-dependent Variable Gearing Mechanism of Muscle-like Soft Actuator ». Journal of Bionic Engineering 19, no 1 (16 décembre 2021) : 29–43. http://dx.doi.org/10.1007/s42235-021-00129-1.
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AbstractPennate muscle is characterized by muscle fibers that are oriented at a certain angle (pennation angle) relative to the muscle’s line of action and rotation during contraction. This fiber rotation amplifies the shortening velocity of muscle, to match loading conditions without any control system. This unique variable gearing mechanism, which characterized by Architecture Gear Ratio (AGR), is involves complex interaction among three key elements: muscle fibers, connective tissue, and the pennation angle. However, how three elements determine the AGR of muscle-like actuator is still unknown. This study introduces a Himisk actuator that arranges five contractile units at a certain pennation angle in a flexible matrix, the experiment and simulation results demonstrated that the proposed actuator could vary AGR automatically in response to variable loading conditions. Based on this actuator, we present a series of actuators by simulations with the varying pennation angle (P), elastic modulus of the flexible matrix (E), and number of contractile units (N) to analyze their effects on AGR, and their interaction by three-factor analysis of variance. The results demonstrated that P and N effect on the AGR significantly, while E effects on AGR slightly, which supported the idea that the P is the essential factor for the AGR, and N is also an important factor due to the capability of force generation. This provides a better understanding of mechanical behavior and an effective optimizing strategy to muscle-like soft actuator.
10
Wakeling, J. M., et I. A. Johnston. « Muscle power output limits fast-start performance in fish. » Journal of Experimental Biology 201, no 10 (15 mai 1998) : 1505–26. http://dx.doi.org/10.1242/jeb.201.10.1505.
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Fast-starts associated with escape responses were filmed at the median habitat temperatures of six teleost fish: Notothenia coriiceps and Notothenia rossii (Antarctica), Myoxocephalus scorpius (North Sea), Scorpaena notata and Serranus cabrilla (Mediterranean) and Paracirrhites forsteri (Indo-West-Pacific Ocean). Methods are presented for estimating the spine positions for silhouettes of swimming fish. These methods were used to validate techniques for calculating kinematics and muscle dynamics during fast-starts. The starts from all species show common patterns, with waves of body curvature travelling from head to tail and increasing in amplitude. Cross-validation with sonomicrometry studies allowed gearing ratios between the red and white muscle to be calculated. Gearing ratios must decrease towards the tail with a corresponding change in muscle geometry, resulting in similar white muscle fibre strains in all the myotomes during the start. A work-loop technique was used to measure mean muscle power output at similar strain and shortening durations to those found in vivo. The fast Sc. notata myotomal fibres produced a mean muscle-mass-specific power of 142.7 W kg-1 at 20 degrees C. Velocity, acceleration and hydrodynamic power output increased both with the travelling rate of the wave of body curvature and with the habitat temperature. At all temperatures, the predicted mean muscle-mass-specific power outputs, as calculated from swimming sequences, were similar to the muscle power outputs measured from work-loop experiments.
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Bohm, Sebastian, Falk Mersmann, Alessandro Santuz et Adamantios Arampatzis. « The force–length–velocity potential of the human soleus muscle is related to the energetic cost of running ». Proceedings of the Royal Society B : Biological Sciences 286, no 1917 (18 décembre 2019) : 20192560. http://dx.doi.org/10.1098/rspb.2019.2560.
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According to the force–length–velocity relationships, the muscle force potential is determined by the operating length and velocity, which affects the energetic cost of contraction. During running, the human soleus muscle produces mechanical work through active shortening and provides the majority of propulsion. The trade-off between work production and alterations of the force–length and force–velocity potentials (i.e. fraction of maximum force according to the force–length–velocity curves) might mediate the energetic cost of running. By mapping the operating length and velocity of the soleus fascicles onto the experimentally assessed force–length and force–velocity curves, we investigated the association between the energetic cost and the force–length–velocity potentials during running. The fascicles operated close to optimal length (0.90 ± 0.10 L 0 ) with moderate velocity (0.118 ± 0.039 V max [maximum shortening velocity]) and, thus, with a force–length potential of 0.92 ± 0.07 and a force–velocity potential of 0.63 ± 0.09. The overall force–length–velocity potential was inversely related ( r = −0.52, p = 0.02) to the energetic cost, mainly determined by a reduced shortening velocity. Lower shortening velocity was largely explained ( p < 0.001, R 2 = 0.928) by greater tendon gearing, shorter Achilles tendon lever arm, greater muscle belly gearing and smaller ankle angle velocity. Here, we provide the first experimental evidence that lower shortening velocities of the soleus muscle improve running economy.
12
Randhawa, Avleen, Meghan E. Jackman et James M. Wakeling. « Muscle gearing during isotonic and isokinetic movements in the ankle plantarflexors ». European Journal of Applied Physiology 113, no 2 (10 juillet 2012) : 437–47. http://dx.doi.org/10.1007/s00421-012-2448-z.
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Balint, Claire N., et Michael H. Dickinson. « The correlation between wing kinematics and steering muscle activity in the blowfly Calliphora vicina ». Journal of Experimental Biology 204, no 24 (15 décembre 2001) : 4213–26. http://dx.doi.org/10.1242/jeb.204.24.4213.
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SUMMARY Determining how the motor patterns of the nervous system are converted into the mechanical and behavioral output of the body is a central goal in the study of locomotion. In the case of dipteran flight, a population of small steering muscles controls many of the subtle changes in wing kinematics that allow flies to maneuver rapidly. We filmed the wing motion of tethered Calliphora vicina at high speed and simultaneously recorded multi-channel electromyographic signals from some of the prominent steering muscles in order to correlate kinematics with muscle activity. Using this analysis, we found that the timing of each spike in the basalare muscles was strongly correlated with changes in the deviation of the stroke plane during the downstroke. The relationship was non-linear such that the magnitude of the kinematic response to each muscle spike decreased with increasing levels of stroke deviation. This result suggests that downstroke deviation is controlled in part via the mechanical summation of basalare activity. We also found that interactions among the basalares and muscles III2–III4 determine the maximum forward amplitude of the wingstroke. In addition, activity in muscle I1 appears to participate in a wingbeat gearing mechanism, as previously proposed. Using these results, we have been able to correlate changes in wing kinematics with alteration in the spike rate, firing phase and combinatorial activity of identified steering muscles.
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Holt, Natalie C., Nicole Danos, Thomas J. Roberts et Emanuel Azizi. « Stuck in gear : age-related loss of variable gearing in skeletal muscle ». Journal of Experimental Biology 219, no 7 (30 mars 2016) : 998–1003. http://dx.doi.org/10.1242/jeb.133009.
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Wakeling, James M., et Avleen Randhawa. « Transverse Strains in Muscle Fascicles during Voluntary Contraction : A 2D Frequency Decomposition of B-Mode Ultrasound Images ». International Journal of Biomedical Imaging 2014 (2014) : 1–9. http://dx.doi.org/10.1155/2014/352910.
Texte intégralRésumé :
When skeletal muscle fibres shorten, they must increase in their transverse dimensions in order to maintain a constant volume. In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing. Understanding the nature and extent of this transverse expansion is necessary to understand the mechanisms driving the changes in internal geometry of whole muscles during contraction. Current methodologies allow the fascicle lengths, orientations, and curvatures to be quantified, but not the transverse expansion. The purpose of this study was to develop and validate techniques for quantifying transverse strain in skeletal muscle fascicles during contraction from B-mode ultrasound images. Images were acquired from the medial and lateral gastrocnemii during cyclic contractions, enhanced using multiscale vessel enhancement filtering and the spatial frequencies resolved using 2D discrete Fourier transforms. The frequency information was resolved into the fascicle orientations that were validated against manually digitized values. The transverse fascicle strains were calculated from their wavelengths within the images. These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.
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Fahn-Lai, Philip, Andrew A. Biewener et Stephanie E. Pierce. « Broad similarities in shoulder muscle architecture and organization across two amniotes : implications for reconstructing non-mammalian synapsids ». PeerJ 8 (18 février 2020) : e8556. http://dx.doi.org/10.7717/peerj.8556.
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The evolution of upright limb posture in mammals may have enabled modifications of the forelimb for diverse locomotor ecologies. A rich fossil record of non-mammalian synapsids holds the key to unraveling the transition from “sprawling” to “erect” limb function in the precursors to mammals, but a detailed understanding of muscle functional anatomy is a necessary prerequisite to reconstructing postural evolution in fossils. Here we characterize the gross morphology and internal architecture of muscles crossing the shoulder joint in two morphologically-conservative extant amniotes that form a phylogenetic and morpho-functional bracket for non-mammalian synapsids: the Argentine black and white tegu Salvator merianae and the Virginia opossum Didelphis virginiana. By combining traditional physical dissection of cadavers with nondestructive three-dimensional digital dissection, we find striking similarities in muscle organization and architectural parameters. Despite the wide phylogenetic gap between our study species, distal muscle attachments are notably similar, while differences in proximal muscle attachments are driven by modifications to the skeletal anatomy of the pectoral girdle that are well-documented in transitional synapsid fossils. Further, correlates for force production, physiological cross-sectional area (PCSA), muscle gearing (pennation), and working range (fascicle length) are statistically indistinguishable for an unexpected number of muscles. Functional tradeoffs between force production and working range reveal muscle specializations that may facilitate increased girdle mobility, weight support, and active stabilization of the shoulder in the opossum—a possible signal of postural transformation. Together, these results create a foundation for reconstructing the musculoskeletal anatomy of the non-mammalian synapsid pectoral girdle with greater confidence, as we demonstrate by inferring shoulder muscle PCSAs in the fossil non-mammalian cynodont Massetognathus pascuali.
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Richards, Christopher T., et Christofer J. Clemente. « Built for rowing : frog muscle is tuned to limb morphology to power swimming ». Journal of The Royal Society Interface 10, no 84 (6 juillet 2013) : 20130236. http://dx.doi.org/10.1098/rsif.2013.0236.
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Rowing is demanding, in part, because drag on the oars increases as the square of their speed. Hence, as muscles shorten faster, their force capacity falls, whereas drag rises. How do frogs resolve this dilemma to swim rapidly? We predicted that shortening velocity cannot exceed a terminal velocity where muscle and fluid torques balance. This terminal velocity, which is below V max , depends on gear ratio (GR = outlever/inlever) and webbed foot area. Perhaps such properties of swimmers are ‘tuned’, enabling shortening speeds of approximately 0.3 V max for maximal power. Predictions were tested using a ‘musculo-robotic’ Xenopus laevis foot driven either by a living in vitro or computational in silico plantaris longus muscle. Experiments verified predictions. Our principle finding is that GR ranges from 11.5 to 20 near the predicted optimum for rowing (GR ≈ 11). However, gearing influences muscle power more strongly than foot area. No single morphology is optimal for producing muscle power. Rather, the ‘optimal’ GR decreases with foot size, implying that rowing ability need not compromise jumping (and vice versa ). Thus, despite our neglect of additional forces (e.g. added mass), our model predicts pairings of physiological and morphological properties to confer effective rowing. Beyond frogs, the model may apply across a range of size and complexity from aquatic insects to human-powered rowing.
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Nandor, Mark J., Maryellen Heebner, Roger Quinn, Ronald J. Triolo et Nathaniel S. Makowski. « Transmission Comparison for Cooperative Robotic Applications ». Actuators 10, no 9 (25 août 2021) : 203. http://dx.doi.org/10.3390/act10090203.
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The development of powered assistive devices that integrate exoskeletal motors and muscle activation for gait restoration benefits from actuators with low backdrive torque. Such an approach enables motors to assist as needed while maximizing the joint torque muscles, contributing to movement, and facilitating ballistic motions instead of overcoming passive dynamics. Two electromechanical actuators were developed to determine the effect of two candidate transmission implementations for an exoskeletal joint. To differentiate the transmission effects, the devices utilized the same motor and similar gearing. One actuator included a commercially available harmonic drive transmission while the other incorporated a custom designed two-stage planetary transmission. Passive resistance and mechanical efficiency were determined based on isometric torque and passive resistance. The planetary-based actuator outperformed the harmonic-based actuator in all tests and would be more suitable for hybrid exoskeletons.
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Usherwood, J. R., et N. W. Gladman. « Why are the fastest runners of intermediate size ? Contrasting scaling of mechanical demands and muscle supply of work and power ». Biology Letters 16, no 10 (octobre 2020) : 20200579. http://dx.doi.org/10.1098/rsbl.2020.0579.
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The fastest land animals are of intermediate size. Cheetah, antelope, greyhounds and racehorses have been measured running much faster than reported for elephants or elephant shrews. Can this be attributed to scaling of physical demands and explicit physiological constraints to supply? Here, we describe the scaling of mechanical work demand each stride, and the mechanical power demand each stance. Unlike muscle stress, strain and strain rate, these mechanical demands cannot be circumvented by changing the muscle gearing with minor adaptations in bone geometry or trivial adjustments to limb posture. Constraints to the capacity of muscle to supply work and power impose fundamental limitations to maximum speed. Given an upper limit to muscle work capacity each contraction, maximum speeds in big animals are constrained by the mechanical work demand each step. With an upper limit to instantaneous muscle power production, maximal speeds in small animals are limited by the high power demands during brief stance periods. The high maximum speed of the cheetah may therefore be attributed as much to its size as to its other anatomical and physiological adaptations.
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Monte, Andrea, Paolo Tecchio, Francesca Nardello, Beatriz Bachero‐Mena, Luca Paolo Ardigò et Paola Zamparo. « Influence of muscle‐belly and tendon gearing on the energy cost of human walking ». Scandinavian Journal of Medicine & ; Science in Sports 32, no 5 (14 février 2022) : 844–55. http://dx.doi.org/10.1111/sms.14142.
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Allen, V. R., R. E. Kambic, S. M. Gatesy et J. R. Hutchinson. « Gearing effects of the patella (knee extensor muscle sesamoid) of the helmeted guineafowl during terrestrial locomotion ». Journal of Zoology 303, no 3 (19 juillet 2017) : 178–87. http://dx.doi.org/10.1111/jzo.12485.
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Monte, Andrea, et Andrea Zignoli. « Muscle and tendon stiffness and belly gearing positively correlate with rate of torque development during explosive fixed end contractions ». Journal of Biomechanics 114 (janvier 2021) : 110110. http://dx.doi.org/10.1016/j.jbiomech.2020.110110.
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Azizi, E., E. L. Brainerd et T. J. Roberts. « Variable gearing in pennate muscles ». Proceedings of the National Academy of Sciences 105, no 5 (29 janvier 2008) : 1745–50. http://dx.doi.org/10.1073/pnas.0709212105.
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Smith, Ross, Glen Lichtwark, Dominic Farris et Luke A. Kelly. « Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing ». Footwear Science 13, sup1 (1 juillet 2021) : S87—S89. http://dx.doi.org/10.1080/19424280.2021.1917696.
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Son, Jongsang, et William Zev Rymer. « Loss of variable fascicle gearing during voluntary isometric contractions of paretic medial gastrocnemius muscles in male chronic stroke survivors ». Journal of Physiology 598, no 22 (9 septembre 2020) : 5183–94. http://dx.doi.org/10.1113/jp280126.
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Kończak, Michał, Mateusz Kukla et Dominik Rybarczyk. « Design Considerations Concerning an Innovative Drive System for a Manual Wheelchair ». Applied Sciences 14, no 15 (28 juillet 2024) : 6604. http://dx.doi.org/10.3390/app14156604.
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Manual wheelchairs, which are the basic means of transport for people with disabilities, are usually characterized by an inefficient adaptation to the physical capabilities of their users. For this reason, it is advisable to search for solutions that will allow us to change the parameters of the mechanical power generated by human muscles. For this purpose, mechanical gearing known from other solutions, for example, from bicycles, can be used. The paper describes the design methodology and a number of issues related to the construction of an innovative wheelchair prototype using a chain transmission in its drive system. This solution allows for the implementation of a variable ratio between the wheels and the pushrims. Thus, it effectively allows for matching the demand for driving torque to the movement conditions and the physical capabilities of its user. The use of such a system provides the basis for increasing the efficiency of the manual propulsion process. Initial studies show that changing the gear ratio allows for different speeds of the wheelchair wheel. In the tests conducted, the root mean square of this value varied from 15.2 RPM to 35.5 RPM, which resulted in a change in power from 15.8 W to 40.1 W. Of course, the values of rotational speed and torque show a cyclically changing character, which results from the intermittent nature of generating drive by the wheelchair user. The average peak values of rotational speed were 31.4 ± 1.7 RPM, 44.3 ± 3.4 RPM and 57.9 ± 3.4 RPM, while the torque was 12.1 ± 0.5 Nm, 12.4 ± 0.4 Nm and 14.1 ± 0.6 Nm for Gears 1, 4 and 6, respectively.
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Kelp, Nicole Y., Christofer J. Clemente, Kylie Tucker, François Hug, Sabrina Pinel et Taylor J. M. Dick. « Influence of internal muscle properties on muscle shape change and gearing in the human gastrocnemii ». Journal of Applied Physiology, 11 mai 2023. http://dx.doi.org/10.1152/japplphysiol.00080.2023.
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Skeletal muscles bulge when they contract. These three-dimensional shape changes coupled with fibre rotation, influence a muscle's mechanical performance by uncoupling fibre velocity from muscle belly velocity (i.e., gearing). Muscle shape change and gearing is likely mediated by the interaction between internal muscle properties and contractile forces. Muscles with greater stiffness and intermuscular fat, due to aging or disuse, may limit a muscle's ability to bulge in width, subsequently causing higher gearing. The aim of this study was to determine the influence of internal muscle properties on shape change, fibre rotation, and gearing in the medial (MG) and lateral gastrocnemii (LG) during isometric plantarflexion contractions. Multi-modal imaging techniques were used to measure muscle shear modulus, intramuscular fat, and fat-corrected physiological cross-sectional area (PCSA), at rest, as well as synchronous muscle architecture changes during submaximal and maximal contractions in the MG and LG of 20 young (24±3y) and 13 older (70±4y) participants. Fat-corrected PCSA was positively associated with fibre rotation, gearing, and changes in thickness during submaximal contractions, but negatively associated with changes in thickness at maximal contractions. Muscle stiffness and intramuscular fat were related to muscle bulging and reduced fibre rotation, respectively, but only at high forces. Further, the MG and LG had varied internal muscle properties, which may relate to the differing shape changes, fibre rotations and gearing behaviours observed at each contraction level. These results indicate that internal muscle properties may play an important role in mediating muscle shape change and gearing, especially during high force contractions.
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Monte, Andrea, et Paola Zamparo. « Impairments in muscle shape changes affect metabolic demands during in-vivo contractions ». Proceedings of the Royal Society B : Biological Sciences 290, no 2006 (6 septembre 2023). http://dx.doi.org/10.1098/rspb.2023.1469.
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The uncoupling behaviour between muscle belly and fascicle shortening velocity (i.e. belly gearing), affects mechanical output by allowing the muscle to circumvent the limits imposed by the fascicles' force-velocity relationship. However, little is known about the ‘metabolic effect' of a decrease/increase in belly gearing. In this study, we manipulated the plantar flexor muscles' capacity to change in shape (and hence belly gearing) by using compressive multidirectional loads. Metabolic, kinetic, electromyography activity and ultrasound data (in soleus and gastrocnemius medialis) were recorded during cyclic fixed-end contractions of the plantar flexor muscles in three different conditions: no load, +5 kg and +10 kg of compression. No differences were observed in mechanical power and electrophysiological variables as a function of compression intensity, whereas metabolic power increased as a function of it. At each compression intensity, differences in efficiency were observed when calculated based on fascicle or muscle behaviour and significant positive correlations ( R 2 range: 0.7–0.8 and p > 0.001) were observed between delta efficiency (ΔEff: Eff mus −Eff fas ) and belly gearing ( V mus / V fas ) or ΔV ( V mus − V fas ). Thus, changes in the muscles' capacity to change in shape (e.g. in muscle stiffness or owing to compressive garments) affect the metabolic demands and the efficiency of muscle contraction.
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Coenning, Corinna, Volker Rieg, Tobias Siebert et Veit Wank. « Impact of contraction intensity and ankle joint angle on calf muscle fascicle length and pennation angle during isometric and dynamic contractions ». Scientific Reports 14, no 1 (22 octobre 2024). http://dx.doi.org/10.1038/s41598-024-75795-2.
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AbstractDuring muscle contraction, not only are the fascicles shortening but also the pennation angle changes, which leads to a faster contraction of the muscle than of its fascicles. This phenomenon is called muscle gearing, and it has a direct influence on the force output of the muscle. There are few studies showing pennation angle changes during isometric and concentric contractions for different contraction intensities and muscle lengths. Therefore, the aim was to determine these influences over a wide range of contraction intensities and ankle joint angles for human triceps surae. Additionally, the influence of contraction intensity and ankle joint angle on muscle gearing was evaluated. Ten sport students performed concentric and isometric contractions with intensities between 0 and 90% of the maximum voluntary contraction and ankle joint angles from 50° to 120°. During these contractions, the m. gastrocnemius medialis and lateralis and the m. soleus were recorded via ultrasound imaging. A nonlinear relationship between fascicle length and pennation angle was discovered, which can be described with a quadratic fit for each of the muscles during isometric contraction. A nearly identical relationship was detected during dynamic contraction. The muscle gearing increased almost linearly with contraction intensity and ankle joint angle.
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Takahashi, Katsuki, Hiroto Shiotani, Pavlos E. Evangelidis, Natsuki Sado et Yasuo Kawakami. « Coronal as well as Sagittal Fascicle Dynamics Can Bring About a Gearing Effect in Muscle Elongation by Passive Lengthening ». Medicine & ; Science in Sports & ; Exercise, 30 juin 2023. http://dx.doi.org/10.1249/mss.0000000000003229.
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ABSTRACT Purpose The amount of muscle belly elongation induced by passive lengthening is often assumed to be equal to that of fascicles. But these are different if fascicles shorter than the muscle belly rotate around their attachment sites. Such discrepancy between fascicles and muscle belly length changes can be considered as gearing. As the muscle fascicle arrangement is three-dimensional, the fascicle rotation by passive lengthening may occur in the coronal as well as the sagittal planes. Here we examined the fascicle 3D dynamics and resultant gearing during passive elongation of human medial gastrocnemius in vivo. Methods For 16 healthy adults, we reconstructed fascicles three-dimensionally using diffusion tensor imaging and evaluated the change in fascicle length and angles in the sagittal and coronal planes during passive ankle dorsiflexion (from 20° plantar flexion to 20° dorsiflexion). Results Whole muscle belly elongation during passive ankle dorsiflexion was 38% greater than the fascicle elongation. Upon passive lengthening, the fascicle angle in the sagittal plane in all regions (–5.9°) and that in the coronal plane in the middle-medial (–2.7°) and distal-medial (–4.3°) regions decreased significantly. Combining the fascicle coronal and sagittal rotation significantly increased the gearing effects in the middle-medial (+10%) and distal-medial (+23%) regions. The gearing effect by fascicle sagittal and coronal rotations corresponded to 26% of fascicle elongation, accounting for 19% of whole muscle belly elongation. Conclusions Fascicle rotation in the coronal and sagittal planes is responsible for passive gearing contributing to the whole muscle belly elongation. Passive gearing can be favorable for reducing fascicle elongation for a given muscle belly elongation.
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Monte, Andrea, Matteo Bertucco, Riccardo Magris et Paola Zamparo. « Muscle Belly Gearing Positively Affects the Force–Velocity and Power–Velocity Relationships During Explosive Dynamic Contractions ». Frontiers in Physiology 12 (12 août 2021). http://dx.doi.org/10.3389/fphys.2021.683931.
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Changes in muscle shape could play an important role during contraction allowing to circumvent some limits imposed by the fascicle force–velocity (F–V) and power–velocity (P–V) relationships. Indeed, during low-force high-velocity contractions, muscle belly shortening velocity could exceed muscle fascicles shortening velocity, allowing the muscles to operate at higher F–V and P–V potentials (i.e., at a higher fraction of maximal force/power in accordance to the F–V and P–V relationships). By using an ultrafast ultrasound, we investigated the role of muscle shape changes (vastus lateralis) in determining belly gearing (muscle belly velocity/fascicle velocity) and the explosive torque during explosive dynamic contractions (EDC) at angular accelerations ranging from 1000 to 4000°.s–2. By means of ultrasound and dynamometric data, the F–V and P–V relationships both for fascicles and for the muscle belly were assessed. During EDC, fascicle velocity, belly velocity, belly gearing, and knee extensors torque data were analysed from 0 to 150 ms after torque onset; the fascicles and belly F–V and P–V potentials were thus calculated for each EDC. Absolute torque decreased as a function of angular acceleration (from 80 to 71 Nm, for EDC at 1000 and 4000°.s–1, respectively), whereas fascicle velocity and belly velocity increased with angular acceleration (P < 0.001). Belly gearing increased from 1.11 to 1.23 (or EDC at 1000 and 4000°.s–1, respectively) and was positively corelated with the changes in muscle thickness and pennation angle (the changes in latter two equally contributing to belly gearing changes). For the same amount of muscle’s mechanical output (force or power), the fascicles operated at higher F–V and P–V potential than the muscle belly (e.g., P–V potential from 0.70 to 0.56 for fascicles and from 0.65 to 0.41 for the muscle belly, respectively). The present results experimentally demonstrate that belly gearing could play an important role during explosive contractions, accommodating the largest part of changes in contraction velocity and allowing the fascicle to operate at higher F–V and P–V potentials.
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Polet, Delyle T., et David Labonte. « Optimal Gearing of Musculoskeletal Systems ». Integrative And Comparative Biology, 20 juin 2024. http://dx.doi.org/10.1093/icb/icae072.
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Abstract Movement is integral to animal life, and most animal movement is actuated by the same engine: striated muscle. Muscle input is typically mediated by skeletal elements, resulting in musculoskeletal systems that are geared: at any instant, the muscle force and velocity are related to the output force and velocity only via a proportionality constant G, the “mechanical advantage”. The functional analysis of such “simple machines” has traditionally centred around this instantaneous interpretation, such that a small vs large G is thought to reflect a fast vs forceful system, respectively. But evidence is mounting that a comprehensive analysis ought to also consider the mechanical energy output of a complete contraction. Here, we approach this task systematically, and deploy the theory of physiological similarity to study how gearing affects the flow of mechanical energy in a minimalist model of a musculoskeletal system. Gearing influences the flow of mechanical energy in two key ways: it can curtail muscle work output, because it determines the ratio between the characteristic muscle kinetic energy and work capacity; and it defines how each unit of muscle work is partitioned into different system energies, i.e., into kinetic vs. “parasitic” energy such as heat. As a consequence of both effects, delivering maximum work in minimum time and with maximum output speed generally requires a mechanical advantage of intermediate magnitude. This optimality condition can be expressed in terms of two dimensionless numbers that reflect the key geometric, physiological, and physical properties of the interrogated musculoskeletal system, and the environment in which the contraction takes place. Illustrative application to exemplar musculoskeletal systems predicts plausible mechanical advantages in disparate biomechanical scenarios; yields a speculative explanation for why gearing is typically used to attenuate the instantaneous force output (Gopt < 1); and predicts how G needs to vary systematically with animal size to optimise the delivery of mechanical energy, in superficial agreement with empirical observations. A many-to-one-mapping from musculoskeletal geometry to mechanical performance is identified, such that differences in G alone do not provide a reliable indicator for specialisation for force vs speed—neither instantaneously, nor in terms of mechanical energy output. The energy framework presented here can be used to estimate an optimal mechanical advantage across variable muscle physiology, anatomy, mechanical environment and animal size, and so facilitates investigation of the extent to which selection has made efficient use of gearing as degree of freedom in musculoskeletal “design”.
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Van Hooren, Bas, Per Aagaard, Andrea Monte et Anthony J. Blazevich. « The role of pennation angle and architectural gearing to rate of force development in dynamic and isometric muscle contractions ». Scandinavian Journal of Medicine & ; Science in Sports 34, no 5 (30 avril 2024). http://dx.doi.org/10.1111/sms.14639.
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AbstractBackgroundAssociations between muscle architecture and rate of force development (RFD) have been largely studied during fixed‐end (isometric) contractions. Fixed‐end contractions may, however, limit muscle shape changes and thus alter the relationship between muscle architecture an RFD.AimWe compared the correlation between muscle architecture and architectural gearing and knee extensor RFD when assessed during dynamic versus fixed‐end contractions.MethodsTwenty‐two recreationally active male runners performed dynamic knee extensions at constant acceleration (2000°s−2) and isometric contractions at a fixed knee joint angle (fixed‐end contractions). Torque, RFD, vastus lateralis muscle thickness, and fascicle dynamics were compared during 0–75 and 75–150 ms after contraction onset.ResultsResting fascicle angle was moderately and positively correlated with RFD during fixed‐end contractions (r = 0.42 and 0.46 from 0–75 and 75–150 ms, respectively; p < 0.05), while more strongly (p < 0.05) correlated with RFD during dynamic contractions (r = 0.69 and 0.73 at 0–75 and 75–150 ms, respectively; p < 0.05). Resting fascicle angle was (very) strongly correlated with architectural gearing (r = 0.51 and 0.73 at 0–75 ms and 0.50 and 0.70 at 75–150 ms; p < 0.05), with gearing in turn also being moderately to strongly correlated with RFD in both contraction conditions (r = 0.38–0.68).ConclusionResting fascicle angle was positively correlated with RFD, with a stronger relationship observed in dynamic than isometric contraction conditions. The stronger relationships observed during dynamic muscle actions likely result from different restrictions on the acute changes in muscle shape and architectural gearing imposed by isometric versus dynamic muscle contractions.
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Zeininger, Angel, Daniel Schmitt, Jody L. Jensen et Liza J. Shapiro. « Variable gearing at the ankle during walking in adults and young children : implications for foot development and evolution ». Frontiers in Earth Science 12 (12 juin 2024). http://dx.doi.org/10.3389/feart.2024.1348921.
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Introduction: The human foot has evolved over the past seven million years from a relatively mobile, grasping appendage to a highly derived structure with a heel pad and longitudinal arch that can absorb shock at heel strike and weight-bearing yet also function as a powerful lever at toe-off. It has been proposed that the modern human foot evolved to allow our species to use “variable gearing” during walking and running. In this model, the gears of the human foot are defined relative to the ankle center of rotation as R, the distance from the ground reaction resultant vector, and r, the distance from the calf muscle vector. The gear ratio defines the torque generated to propel the body or stretch the triceps surae muscles. We test the hypothesis that variable gearing is associated with modern human pedal anatomy and a heel-to-toe rollover that allows a shift from “low gear” to “high gear” during stance.Methods: Using force plate and video analysis, we examined variable gearing in adults and children engaging in adult heel strike (AHS = 35), flat foot contact (FFC = 39), or initial heel contact (IHC = 26).Results and Discussion: Our hypothesis was partly supported. Although variable gearing was observed in IHC steps and was greater than in FFC steps, it was not as developed as in AHS steps. This may be related to anatomical and motor control differences between juvenile and adult feet, suggesting that adult anatomy, including a high arch, and neural control are critical for full use of variable gearing and that this feature would have evolved in later hominins around two million years ago with the appearance of a fully modern foot.
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Tijs, Chris, Nicolai Konow et Andrew A. Biewener. « Effect of muscle stimulation intensity on the heterogeneous function of regions within an architecturally complex muscle ». Journal of Applied Physiology, 7 janvier 2021. http://dx.doi.org/10.1152/japplphysiol.00514.2020.
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Skeletal muscle has fiber architectures ranging from simple to complex, alongside variation in fiber-type and neuro-anatomical compartmentalization. However, the functional implications of muscle subdivision into discrete functional units remain poorly understood. The rat medial gastrocnemius has well-characterized regions with distinct architectures and fiber type composition. Here, force-length and force-velocity contractions were performed for two stimulation intensities (supramaximal and submaximal) and for three structural units (whole muscle belly, proximal region and distal region) to assess the effect of muscle compartmentalization on contractile force-length-velocity relations and optimal speed for power production. Additionally, fiber strain, fiber rotation, pennation, and architectural gearing were quantified. Our results suggest that the proximal and distal muscle regions have fundamentally different physiological function. During supramaximal activation, the proximal region has shorter (8.4±0.8mm vs 10.9±0.7mm) fibers and steeper (28.7±11.0° vs 19.6±6.3°) fiber angles at optimum length, and operates over a larger (17.9 ± 3.8% vs 12.6 ± 2.7%) range of its force-length curve. The proximal region also exhibits larger changes in pennation angle (5.6 ± 2.2°/mm vs 2.4 ± 1.5°/mm muscle shortening) and architectural gearing (1.82 ± 0.53 vs 1.25 ± 0.24); whereas, the distal region exhibits greater peak shortening speed (96.0mm/s vs 81.3mm/s) and 18-27% greater optimal speed. Overall, similar patterns were observed during submaximal activation. These regional differences in physiological function with respect to the whole muscle highlight how variation in motor recruitment could fundamentally shift regional functional patterns within a single muscle, which likely has important implications for whole muscle force and work output in vivo.
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Jimenez, Yordano E., Richard L. Marsh et Elizabeth L. Brainerd. « A biomechanical paradox in fish : swimming and suction feeding produce orthogonal strain gradients in the axial musculature ». Scientific Reports 11, no 1 (14 mai 2021). http://dx.doi.org/10.1038/s41598-021-88828-x.
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AbstractThe axial musculature of fishes has historically been characterized as the powerhouse for explosive swimming behaviors. However, recent studies show that some fish also use their ‘swimming’ muscles to generate over 90% of the power for suction feeding. Can the axial musculature achieve high power output for these two mechanically distinct behaviors? Muscle power output is enhanced when all of the fibers within a muscle shorten at optimal velocity. Yet, axial locomotion produces a mediolateral gradient of muscle strain that should force some fibers to shorten too slowly and others too fast. This mechanical problem prompted research into the gearing of fish axial muscle and led to the discovery of helical fiber orientations that homogenize fiber velocities during swimming, but does such a strain gradient also exist and pose a problem for suction feeding? We measured muscle strain in bluegill sunfish, Lepomis macrochirus, and found that suction feeding produces a gradient of longitudinal strain that, unlike the mediolateral gradient for locomotion, occurs along the dorsoventral axis. A dorsoventral strain gradient within a muscle with fiber architecture shown to counteract a mediolateral gradient suggests that bluegill sunfish should not be able to generate high power outputs from the axial muscle during suction feeding—yet prior work shows that they do, up to 438 W kg−1. Solving this biomechanical paradox may be critical to understanding how many fishes have co-opted ‘swimming’ muscles into a suction feeding powerhouse.
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Hodson-Tole, Emma F., James M. Wakeling et Taylor J. M. Dick. « Passive Muscle-Tendon Unit Gearing Is Joint Dependent in Human Medial Gastrocnemius ». Frontiers in Physiology 7 (15 mars 2016). http://dx.doi.org/10.3389/fphys.2016.00095.
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Po, Theodora, Andres Carrillo, Amberle McKee, Bruno Pernet et Matthew J. McHenry. « Gearing in a hydrostatic skeleton : the tube feet of juvenile sea stars (Leptasterias sp.) ». Journal of Experimental Biology, 6 août 2024. http://dx.doi.org/10.1242/jeb.247804.
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Hydrostatic skeletons, such as an elephant trunk or a squid tentacle, permit the transmission of mechanical work through a soft body. Despite the ubiquity of these structures among animals, we generally do not understand how differences in their morphology affect their ability to transmit muscular work. Therefore, the present study used mathematical modeling, morphometrics, and kinematics to understand the transmission of force and displacement in the tube feet of the juvenile six-rayed star (Leptasterias sp.). An inverse-dynamic analysis revealed that the forces generated by the feet during crawling primarily serve to overcome the submerged weight of the body. These forces were disproportionately generated by the feet at more proximal positions along each ray, which were used more frequently for crawling. Due to a combination of mechanical advantage and muscle mass, these proximal feet exhibited a greater capacity for force generation than the distal feet. However, the higher displacement advantage of the more elongated distal feet offer a superior ability to extend the feet into the environment. Therefore, the morphology of tube feet demonstrates a gradient in gearing along each ray that compliments their role in behavior.
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Monte, Andrea, Francesca Nardello, Riccardo Magris, Paolo Tecchio et Paola Zamparo. « The influence of in vivo mechanical behaviour of the Achilles tendon on the mechanics, energetics and apparent efficiency of bouncing gaits ». Journal of Experimental Biology 224, no 16 (15 août 2021). http://dx.doi.org/10.1242/jeb.242453.
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ABSTRACT In this study, we used kinematic, kinetic, metabolic and ultrasound analysis to investigate the role of elastic energy utilization on the mechanical and physiological demands of a movement task (hopping) that primarily involves the plantar-flexor muscles to determine the contribution of tendon work to total mechanical work and its relationship with apparent efficiency (AE) in bouncing gaits. Metabolic power (PMET) and (positive) mechanical power at the whole-body level (PMEC) were measured during hopping at different frequencies (2, 2.5, 3 and 3.5 Hz). The (positive) mechanical power produced during the Achilles tendon recoil phase (PTEN) was obtained by integrating ultrasound data with an inverse dynamic approach. As a function of hopping frequency, PMEC decreased steadily and PMET exhibited a U-shape behaviour, with a minimum at about 3 Hz. AE (PMEC/PMET) showed an opposite trend and was maximal (about 0.50) at the same frequency when PTEN was also highest. Positive correlations were observed: (i) between PTEN and AE (AE=0.22+0.15PTEN, R2=0.67, P<0.001) and the intercept of this relationship indicates the value of AE that should be expected when tendon work is nil; (ii) between AE and tendon gearing (Gt=Δmuscle–tendon unit length/Δmuscle belly length; R2=0.50, P<0.001), where a high Gt indicates that the muscle is contracting more isometrically, thus allowing the movement to be more economical (and efficient); (iii) between Gt and PTEN (R2=0.73, P<0.001), which indicates that Gt could play an important role in the tendon's capability to store and release mechanical power.
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Smith, Ross, Glen Lichtwark, Dominic Farris et Luke Kelly. « Examining the intrinsic foot muscles’ capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping ». Journal of Sport and Health Science, juillet 2022. http://dx.doi.org/10.1016/j.jshs.2022.07.002.
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