Littérature scientifique sur le sujet « Muscle mechanical work »
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Articles de revues sur le sujet "Muscle mechanical work"
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Spinks, Geoffrey M., Nicolas D. Martino, Sina Naficy, David J. Shepherd et Javad Foroughi. « Dual high-stroke and high–work capacity artificial muscles inspired by DNA supercoiling ». Science Robotics 6, no 53 (28 avril 2021) : eabf4788. http://dx.doi.org/10.1126/scirobotics.abf4788.
Texte intégralRésumé :
Powering miniature robots using actuating materials that mimic skeletal muscle is attractive because conventional mechanical drive systems cannot be readily downsized. However, muscle is not the only mechanically active system in nature, and the thousandfold contraction of eukaryotic DNA into the cell nucleus suggests an alternative mechanism for high-stroke artificial muscles. Our analysis reveals that the compaction of DNA generates a mass-normalized mechanical work output exceeding that of skeletal muscle, and this result inspired the development of composite double-helix fibers that reversibly convert twist to DNA-like plectonemic or solenoidal supercoils by simple swelling and deswelling. Our modeling-optimized twisted fibers give contraction strokes as high as 90% with a maximum gravimetric work 36 times higher than skeletal muscle. We found that our supercoiling coiled fibers simultaneously provide high stroke and high work capacity, which is rare in other artificial muscles.
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Ross, Stephanie A., Barbora Rimkus, Nicolai Konow, Andrew A. Biewener et James M. Wakeling. « Added mass in rat plantaris muscle causes a reduction in mechanical work ». Journal of Experimental Biology 223, no 19 (31 juillet 2020) : jeb224410. http://dx.doi.org/10.1242/jeb.224410.
Texte intégralRésumé :
ABSTRACTMost of what we know about whole muscle behaviour comes from experiments on single fibres or small muscles that are scaled up in size without considering the effects of the additional muscle mass. Previous modelling studies have shown that tissue inertia acts to slow the rate of force development and maximum velocity of muscle during shortening contractions and decreases the work and power per cycle during cyclic contractions; however, these results have not yet been confirmed by experiments on living tissue. Therefore, in this study we conducted in situ work-loop experiments on rat plantaris muscle to determine the effects of increasing the mass of muscle on mechanical work during cyclic contractions. We additionally simulated these experimental contractions using a mass-enhanced Hill-type model to validate our previous modelling work. We found that greater added mass resulted in lower mechanical work per cycle relative to the unloaded trials in which no mass was added to the muscle (P=0.041 for both 85 and 123% increases in muscle mass). We additionally found that greater strain resulted in lower work per cycle relative to unloaded trials at the same strain to control for length change and velocity effects on the work output, possibly due to greater accelerations of the muscle mass at higher strains. These results confirm that tissue mass reduces muscle mechanical work at larger muscle sizes, and that this effect is likely amplified for lower activations.
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Caiozzo, V. J., et K. M. Baldwin. « Determinants of work produced by skeletal muscle : potential limitations of activation and relaxation ». American Journal of Physiology-Cell Physiology 273, no 3 (1 septembre 1997) : C1049—C1056. http://dx.doi.org/10.1152/ajpcell.1997.273.3.c1049.
Texte intégralRésumé :
The objective of this study was to estimate the limitations imposed by the kinetics of activation and relaxation on the ability of slow skeletal muscle to produce mechanical work. These estimates were made by the following methods: 1) using the work loop technique and measuring the actual mechanical work (WA) produced by rat soleus muscles (n = 6) at four different frequencies (0.5, 1, 2, and 4 Hz) and seven different amplitudes of length change (1, 2, 3, 4, 5, 6, and 7 mm); 2) determining the force-velocity relationships of the soleus muscles and using this data to quantify the theoretical mechanical work (WT) that could be produced under the work loop conditions described above; and 3) subtracting WA from WT. The difference between WT and WA was interpreted to represent limitations imposed by activation and relaxation. Under certain conditions (high frequency, small strain), factors controlling the kinetics of activation and relaxation reduced the mechanical work of the soleus muscle by approximately 60%. Hence, activation and relaxation collectively represent important factors limiting the production of mechanical work by slow skeletal muscle.
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BOUTILIER, R. G., M. G. EMILIO et G. SHELTON. « The Effects of Mechanical Work on Electrolyte and Water Distribution in Amphibian Skeletal Muscle ». Journal of Experimental Biology 120, no 1 (1 janvier 1986) : 333–50. http://dx.doi.org/10.1242/jeb.120.1.333.
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The present experiments were undertaken to confirm whether the increase in haematocrit that consistently accompanies the build-up of lactate in amphibian muscle cells during exercise can be explained in terms of a movement of water from the blood into the active muscles. Electrically stimulated sartorius and gastrocnemius muscles isolated from Rana ridibunda and Xenopus laevis had consistently higher total water contents than their paired control muscles. In both instances, it was the intracellular water volume which gave rise to the increase in total muscle water. These results were corroborated in vivo by sampling gastrocnemius muscles from exercising and resting Xenopus laevis. Analyses of tissue electrolyte levels in the working muscles of each experimental series showed an increase in intracellular [lactate−] and [Na+]. A corresponding decline in cellular [K+] occurred in concert with increases in extracellular [K+. In saline-perfused gastrocnemii of Xenopus, the uptake of vascular water was proportional to the total mechanical work performed. Saline leaving the femoral vein of isotonically contracting gastrocnemius muscles had a greater osmotic pressure than that of the arterial perfusate, whereas arterio-venous osmolality differences of control muscles were negligible. Calculations show that the haemoconcentration during exercise in vivo can be attributed at least in part to a net flow of plasma water to osmotically enriched muscle cells.
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Olberding, Jeffrey P., Stephen M. Deban, Michael V. Rosario et Emanuel Azizi. « Modeling the Determinants of Mechanical Advantage During Jumping : Consequences for Spring- and Muscle-Driven Movement ». Integrative and Comparative Biology 59, no 6 (9 août 2019) : 1515–24. http://dx.doi.org/10.1093/icb/icz139.
Texte intégralRésumé :
Abstract Systems powered by elastic recoil need a latch to prevent motion while a spring is loaded but allow motion during spring recoil. Some jumping animals that rely on elastic recoil use the increasing mechanical advantage of limb extensor muscles to accomplish latching. We examined the ways in which limb morphology affects latching and the resulting performance of an elastic-recoil mechanism. Additionally, because increasing mechanical advantage is a consequence of limb extension that may be found in many systems, we examined the mechanical consequences for muscle in the absence of elastic elements. By simulating muscle contractions against a simplified model of an extending limb, we found that increasing mechanical advantage can limit the work done by muscle by accelerating muscle shortening during limb extension. The inclusion of a series elastic element dramatically improves mechanical output by allowing for additional muscle work that is stored and released from the spring. This suggests that elastic recoil may be beneficial for more animals than expected when assuming peak isotonic power output from muscle during jumping. The mechanical output of elastic recoil depends on limb morphology; long limbs moving small loads maximize total work, but it is done at a low power, whereas shorter limbs moving larger loads do less work at a higher power. This work-power trade-off of limb morphology is true with or without an elastic element. Systems with relatively short limbs may have performance that is robust to variable conditions such as body mass or muscle activation, while long-limbed systems risk complete failure with relatively minor perturbations. Finally, a changing mechanical advantage latch allows for muscle work to be done simultaneously with spring recoil, changing the predictions for spring mechanical properties. Overall, the design constraints revealed by considering the mechanics of this particular latch will inform our understanding of the evolution of elastic-recoil mechanisms and our attempts to engineer similar systems.
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Sponberg, Simon, Thomas Libby, Chris H. Mullens et Robert J. Full. « Shifts in a single muscle's control potential of body dynamics are determined by mechanical feedback ». Philosophical Transactions of the Royal Society B : Biological Sciences 366, no 1570 (27 mai 2011) : 1606–20. http://dx.doi.org/10.1098/rstb.2010.0368.
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Muscles are multi-functional structures that interface neural and mechanical systems. Muscle work depends on a large multi-dimensional space of stimulus (neural) and strain (mechanical) parameters. In our companion paper, we rewrote activation to individual muscles in intact, behaving cockroaches ( Blaberus discoidalis L.), revealing a specific muscle's potential to control body dynamics in different behaviours. Here, we use those results to provide the biologically relevant parameters for in situ work measurements. We test four hypotheses about how muscle function changes to provide mechanisms for the observed control responses. Under isometric conditions, a graded increase in muscle stress underlies its linear actuation during standing behaviours. Despite typically absorbing energy, this muscle can recruit two separate periods of positive work when controlling running. This functional change arises from mechanical feedback filtering a linear increase in neural activation into nonlinear work output. Changing activation phase again led to positive work recruitment, but at different times, consistent with the muscle's ability to also produce a turn. Changes in muscle work required considering the natural sequence of strides and separating swing and stance contributions of work. Both in vivo control potentials and in situ work loops were necessary to discover the neuromechanical coupling enabling control.
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Milic-Emili, Joseph, et Marcello M. Orzalesi. « Mechanical work of breathing during maximal voluntary ventilation ». Journal of Applied Physiology 85, no 1 (1 juillet 1998) : 254–58. http://dx.doi.org/10.1152/jappl.1998.85.1.254.
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With the use of the esophageal balloon technique, the working capacity of the respiratory muscles was assessed in four normal subjects by measuring the work per breath (W) and respiratory power (W˙) during maximal voluntary ventilation with imposed respiratory frequencies (f) ranging from 20 to 273 cycles/min. Measurements were made in a body plethysmograph to assess the work wasted as a result of alveolar gas compressibility (Wg′). In line with other types of human voluntary muscle activity, W decreased with increasing f, whereasW˙ exhibited a maximum at f of ∼100 cycles/min. Up to this f value, Wg′ was small relative to W. With further increase in f, the Wg′/W ratio increased progressively, amounting to 8–22% of W˙ at f of 200 cycles/min.
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Farris, Dominic James, Benjamin D. Robertson et Gregory S. Sawicki. « Elastic ankle exoskeletons reduce soleus muscle force but not work in human hopping ». Journal of Applied Physiology 115, no 5 (1 septembre 2013) : 579–85. http://dx.doi.org/10.1152/japplphysiol.00253.2013.
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Inspired by elastic energy storage and return in tendons of human leg muscle-tendon units (MTU), exoskeletons often place a spring in parallel with an MTU to assist the MTU. However, this might perturb the normally efficient MTU mechanics and actually increase active muscle mechanical work. This study tested the effects of elastic parallel assistance on MTU mechanics. Participants hopped with and without spring-loaded ankle exoskeletons that assisted plantar flexion. An inverse dynamics analysis, combined with in vivo ultrasound imaging of soleus fascicles and surface electromyography, was used to determine muscle-tendon mechanics and activations. Whole body net metabolic power was obtained from indirect calorimetry. When hopping with spring-loaded exoskeletons, soleus activation was reduced (30–70%) and so was the magnitude of soleus force (peak force reduced by 30%) and the average rate of soleus force generation (by 50%). Although forces were lower, average positive fascicle power remained unchanged, owing to increased fascicle excursion (+4–5 mm). Net metabolic power was reduced with exoskeleton assistance (19%). These findings highlighted that parallel assistance to a muscle with appreciable series elasticity may have some negative consequences, and that the metabolic cost associated with generating force may be more pronounced than the cost of doing work for these muscles.
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James, R. S., V. M. Cox, I. S. Young, J. D. Altringham et D. F. Goldspink. « Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation ». Journal of Applied Physiology 83, no 2 (1 août 1997) : 398–406. http://dx.doi.org/10.1152/jappl.1997.83.2.398.
Texte intégralRésumé :
James, R. S., V. M. Cox, I. S. Young, J. D. Altringham, and D. F. Goldspink Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation. J. Appl. Physiol. 83(2): 398–406, 1997.—The work loop technique was used to measure the mechanical performance in situ of the latissimus dorsi (LD) muscles of rabbits maintained under fentanyl anesthesia. After 3 wk of incrementally applied stretch the LD muscles were 36% heavier, but absolute power output (195 mW/muscle) was not significantly changed relative to that of external control muscle (206 mW). In contrast, continuous 10-Hz electrical stimulation reduced power output per kilogram of muscle >75% after 3 or 6 wk and muscle mass by 32% after 6 wk. When combined, stretch and 10-Hz electrical stimulation preserved or increased the mass of the treated muscles but failed to prevent an 80% loss in maximum muscle power. However, this combined treatment increased fatigue resistance to a greater degree than electrical stimulation alone. These stretched/stimulated muscles, therefore, are more suitable for cardiomyoplasty. Nonetheless, further work will be necessary to find an ideal training program for this surgical procedure.
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Takarada, Yudai, Hiroyuki Iwamoto, Haruo Sugi, Yuichi Hirano et Naokata Ishii. « Stretch-induced enhancement of mechanical work production in frog single fibers and human muscle ». Journal of Applied Physiology 83, no 5 (1 novembre 1997) : 1741–48. http://dx.doi.org/10.1152/jappl.1997.83.5.1741.
Texte intégralRésumé :
Takarada, Yudai, Hiroyuki Iwamoto, Haruo Sugi, Yuichi Hirano, and Naokata Ishii. Stretch-induced enhancement of mechanical work production in frog single fibers and human muscle. J. Appl. Physiol. 83(5): 1741–1748, 1997.—The relations between the velocity of prestretch and the mechanical energy liberated during the subsequent isovelocity release were studied in contractions of frog single fibers and human muscles. During isometric contractions of frog single fibers, a ramp stretch of varied velocity (amplitude, 0.02 fiber length; velocity, 0.08–1.0 fiber length/s) followed by a release (amplitude, 0.02 fiber length; velocity, 1.0 fiber length/s) was given, and the amount of work liberated during the release was measured. For human muscles, elbow flexions were performed with a prestretch of varied velocity (range, 40°; velocity, 30–180°/s) followed by an isokinetic shortening (velocity, 90°/s). In both frog single fibers and human muscles, the work production increased with both the velocity of stretch and the peak of force attained before the release up to a certain level; thereafter it declined with the further increases of these variables. In human muscles, the enhancement of work production was not associated with a significant increase in integrated electromyogram. This suggests that changes in intrinsic mechanical properties of muscle fibers play an important role in the stretch-induced enhancement of work production.
Thèses sur le sujet "Muscle mechanical work"
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Telli, R. « RECUMBENT VS UPRIGHT BICYCLES : OPERATIVE RANGE OF PROPULSIVE MUSCLES, 3D TRAJECTORY OF BODY CENTRE OF MASS AND LIMB MECHANICAL WORK ». Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/243748.
Texte intégralRésumé :
Introduction. Humans have always tried to move safely and faster in a variety of environment, even through the aid of passive tools that help to improve the limits imposed by the body characteristics. These means of locomotion, without supplying additional mechanical energy, are able to greatly improve the performance exploiting the use of muscular force alone. Bicycles are probably the passive tool most known and used in the world. The origin of this thesis comes from the interest to increase the knowledge about the features of a particular kind of bike: the Recumbent bicycle (RB). It is a high performance human powered vehicle where the cyclist is in a reclined position, with the back against a backrest. The peculiarity of the RB is that it allows to reach higher speeds than Normal/upright bicycles (NB), at the same metabolic power, principally due to aerodynamic advantages. Indeed, with the use of particular fairings that improve aerodynamics, these vehicles allow to exceed 130 km/h only with muscles power. The change in posture of the rider, consequent to the different characteristics and design of the bicycles, alters kinematics and energetics of cycling and could also affects muscle-tendon lengths and the operating range of the muscles length-tension curves. Despite the interest of the scientific community on the topic of cycling, some aspects still need to be investigated, especially with respect to the differences between traditional and recumbent bikes, which represent the most advanced evolution of that tool.
Aim. The aim of this work is to analyze and compare the pedalling cycle on both bicycles from a biomechanical point of view. Indeed, with a comprehensive description of mechanical and metabolic consequences during cycling in both configuration, new vehicles could be designed with those technological changes that could increase the performance. Particular focus has been posed on the effect of the different position while riding the two bicycles:
- on the muscle-tendon length of different muscle-tendon unit involved in cycling;
- on the 3D displacement of the Body Centre of Mass (BCoM);
- on the mechanical work (in particular the internal and the "additional" external mechanical work).
Methods. The issues have been investigated both experimentally and trough simulations. By using 3D kinematic data and a physical simulation program we measured muscles-tendon length, 3D Body Centre of Mass (BCoM) trajectory and its symmetries and the components of the total mechanical work necessary to sustain cycling during stationary cycling, at different pedalling cadences (50, 70, 90 and 110 rpm). This approach allows to investigate the biomechanics of riding the two bicycles both through direct measurements of mechanical work and indirect estimation performed with simulation models.
Results and Discussion. Joint kinematics and muscle-tendon length were analyzed with the musculoskeletal modelling software Opensim®. This analysis showed that, differently from cadence, the two bicycles caused changes in joint angles and, consequently, in muscle-tendon length. As a results in RB, when compared to NB, some muscles are slightly stretched while other are shortened, making the propulsive effectiveness impossible to be assessed. This work confirms experimentally, for the first time, that the BCoM in cycling moves along all three spatial axes, while before this study an elliptical movement in the sagittal plane was appreciated only with a 2D simulation. BCoM trajectory, confined in a 15 mm side cube, changed its orientation maintaining a similar pattern in both configurations, with advantages for RB: a smaller additional mechanical external power (on average 16.1 ± 9.7 W on RB versus 20.3 ± 8.8 W on NB), a greater Symmetry Index on progression axis and no differences in the internal mechanical power (ranged from 7.90 W to 65.15 W in NB and from 7.25 W to 62.16 W in RB, increasing as function of the rpm).
Conclusion. Despite the human physiological characteristics have remained almost unchanged over the last millennia, performance on bicycles has increased significantly. This has been possible thanks to the work of mechanical engineers, exercise physiologists and biomechanists. In this thesis the body centre of mass trajectory and the associated additional external mechanical work while pedalling on recumbent bicycle has been studied experimentally for the first time. It is thought that the development of mechanisms reducing additional external power through a further containment of BCoM trajectory, together with additional studies on the effectiveness of propulsive muscles could be necessary to further refine design and improve performance of RB.
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Sundar, Kartik. « The importance of muscle mechanics during movement ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28137.
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Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2009.Committee Chair: DeWeerth, Stephen P.; Committee Co-Chair: Ting, Lena H.; Committee Member: Burkholder, Thomas J.; Committee Member: Nichols, T. Richard; Committee Member: Tresch, Matthew C.
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Long, Benjamin L. DeVita Paul 1955. « Muscle work discrepancy during incline and decline running at three speeds ». [Greenville, N.C.] : East Carolina University, 2009. http://hdl.handle.net/10342/1863.
Texte intégralRésumé :
Thesis (M.S.)--East Carolina University, 2009.Presented to the faculty of the Department of Exercise and Sport Science. Advisor: Paul DeVita. Title from PDF t.p. (viewed May 4, 2010). Includes bibliographical references.
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Grenier, Jordane. « Effets des équipements de fantassin modernes sur la locomotion et la fatigue neuromusculaire du soldat déployé : simulation opérationnelle ». Phd thesis, Université Jean Monnet - Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00978768.
Texte intégralRésumé :
La problématique du port de charges par l'Homme est l'objet de questionnements scientifiques depuis plus d'un siècle, notamment dans les armées où les soldats doivent remplir des objectifs opérationnels tout en emportant des équipements lourds, distribués de façon complexe autour de leur corps, et cela au cours d'efforts allant de quelques heures à plusieurs jours. Aussi, avec le développement des nouvelles technologies et l'arrivée des systèmes fantassins futurs sur le marché de la défense, cette problématique continue de se complexifier puisque la masse totale emportée tend encore à croître. Objectif général : Le but de ce travail de thèse était d'étudier l'impact biomécanique, métabolique et neuromusculaire du port d'un système fantassin moderne chez le soldat expérimenté. Plus précisément, une première recherche a été menée pour caractériser les effets aigus du port d'un tel équipement sur la biomécanique et le coût métabolique de la marche. Puis, une seconde recherche a été consacrée à l'étude des conséquences neuromusculaires et locomotrices d'une mission militaire (simulation sur le terrain) de durée " extrême " réalisée avec ce système fantassin moderne. Première partie : L'analyse de la marche sur tapis roulant dynamométrique a permis de montrer que le port du système fantassin en configurations de " combat " et de " marche d'approche " (principales configurations du théâtre militaire, représentant respectivement ~30 % et ~50 % de la masse corporelle des sujets) altérait le pattern spatio-temporel par rapport à la marche sans charge. Par ailleurs, le travail mécanique appliqué au centre de masse et le coût métabolique de la marche augmentaient parallèlement lors du port des deux configurations du système fantassin, ce qui résultait en un maintien du rendement locomoteur constant dans toutes les conditions testées. Le mécanisme de transfert d'énergie en pendule inversé (méthode Cavagna), permettant de minimiser les coûts mécanique et métabolique de transport, était également similaire dans toutes les conditions avec et sans charge. Enfin, bien que complexement organisés autour du corps du soldat, les équipements militaires n'induisaient pas d'effets mécaniques et métaboliques sensiblement plus importants que ceux rapportés lors du port de masses positionnées symétriquement autour de la taille ; ce mode de portage étant pourtant considéré comme l'un des plus optimisés, abstraction faite des techniques de portage sur la tête inadaptées au contexte militaire. Deuxième partie : La réalisation d'une mission simulée, incluant 21 h d'activités militaires sur le terrain et le port constant d'un système fantassin, résultait en une fatigue neuromusculaire (mesure des forces, électrostimulation et EMG) relativement modérée des muscles locomoteurs extenseurs du genou et fléchisseurs plantaires chez les soldats expérimentés inclus dans ce travail. Les origines de cette fatigue neuromusculaire étaient essentiellement périphériques, mais s'accompagnaient d'une fatigue subjective importante. Enfin, la réalisation de la mission, et donc la fatigue des muscles locomoteurs notamment associée à cette dernière, n'affectait pas sensiblement les paramètres mécaniques et métaboliques de la marche. Conclusion générale : Ce travail rapporte les premières données relatives aux effets biomécaniques, métaboliques et neuromusculaires du port d'un système fantassin moderne chez le soldat expérimenté, et ce par le biais d'une simulation opérationnelle visant à reproduire les conditions militaires
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CONTE, Davide. « Muscle mechanical work in walker-assisted locomotion : Instrumentationand modelling for an integrated gait analysis in cerebral palsy ». Doctoral thesis, 2012. http://hdl.handle.net/11562/417939.
Texte intégralRésumé :
La stima del lavoro meccanico muscolare è un utile strumento per valutare l'efficienza di un movimento, ma il processo di calcolo presenta ancora molte criticità dal punto di vista biomeccanico.
Diversi metodi per stimare il lavoro meccanico muscolare durante il cammino sono stati presentati in letteratura, ma nonostante i tentativi fatti per confrontarli, tutti i metodi sono tuttora utilizzati in ambito di ricerca e in ambito clinico. Una più profonda comprensione delle differenze, sia dal punto di vista teorico, che pratico, potrebbe permettere di capire cosa venga effettivamente calcolato da ciascun metodo ed aiutare a fare un uso più appropriato di questa informazione. A questo scopo è stato validato un modello tridimensionale a corpo completo, consistente in 16 segmenti, utilizzato per raccogliere informazioni cinematiche e dinamiche durante il cammino in ragazzi e bambini sani e in ragazzi e bambini affetti da paralisi cerebrale infantile (CP), camminati a velocità spontanea.
Lo sviluppo di due maniglie strumentate fissabili sulla struttura di deambulatori pediatrici posteriori ha permesso di misurare cinematica e dinamica dell'arto superiore anche in soggetti con maggiori difficoltà di deambulazione. Curve di potenza e valori di lavoro meccanico muscolare totale, positivo, negativo o netto, durante cammino normale e durante cammino con deambulatore, sono stati stimati dimostrando che tutti i metodi sono equivalenti quando vengono permessi trasferimenti di energia tra segmenti. Senza possibilità di trasferimento di energia, i metodi differiscono tra loro, con differenze dipendenti dal metodo utilizzato e dal movimento studiato. Eccetto alcune criticità evidenziate e discusse, l'analisi delle curve di potenza muscolare e dei valori di lavoro meccanico muscolare stimati può fornire utili informazioni sulla funzione locomotoria nel suo complesso, mettendo in luce deficit di propulsione, asimmetrie del cammino, inefficienze di movimento associate ad una ridotta capacità di recupero di energia.The estimation of muscle mechanical work can be useful to assess movement efficiency, but it is still a challenging task in biomechanics. Different methods to estimate muscle work during walking have been presented in the literature and, although attempts have been made to investigate differences among them, all methods are still used in research and clinical applications. A deeper understanding of theoretical differences and analogies would allow to know what is exactly computed by each method and help to make a more appropriate use of this information. To this purpose, a 16 segments full-body 3D model was validated and used to collect kinematic and kinetic data from healthy children and cerebral palsy (CP) children walking at self-selected speed. Two instrumented handles fixable on the frame of posterior paediatric walkers were also developed, to measure upper limb kinetics in subjects with more severe walking impairements. Whole-body muscle mechanical power curves and work values, either positive, negative or net, during normal gait and during walker locomotion were obtained, demonstrating that all methods are equivalent when energy transfers between segments are allowed. With no transfers allowed, methods differ among each other, with differences depending on the movements and the methods considered. Apart from some critical issues evidenced and discussed, the analysis of whole-body muscle mechanical power curves and work estimates can provide valuable information on the overall locomotion function, highlighting propulsive deficits, gait asymmetries, movement inefficiencies associated to reduced energy recuperation.
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Monte, Andrea. « Mechanics and energetics of running at steady and non-steady speed (sprint and shuttles) : the effects of muscle-tendon behaviour ». Doctoral thesis, 2020. http://hdl.handle.net/11562/1019320.
Texte intégralRésumé :
When humans move, they could do it in steady or non-steady conditions. In the former case the speed of locomotion is constant (or with minimal oscillations) and occurs in a definite direction (e.g. walking or running along a linear path), whereas in the latter case the body accelerates, decelerates or moves in different directions. In both cases, the minimum work required to sustain locomotion is given by the product of the resistance offered by the environment and the distance covered. Finally, the efficiency of the locomotor apparatus may be expressed as the ratio between the work necessary to maintain motion and the chemical energy transformed by the muscles. However, whereas the energetics and mechanics of running at constant speed are well known, only few studies have investigated so far non-steady running conditions (e.g. accelerated or decelerated running as well as running with changes of direction). The role of muscles and tendons in determining the mechanical and physiological responses during human locomotion is another topic that needs to be further investigated, both in steady and unsteady conditions. As an example, when humans run at constant speed muscles and tendons stretch and recoil; into this succession of stretch-shortening cycles, tendons could play an important role as energy savers allowing this form of locomotion to be particularly efficient. Locomotion (apparent) efficiency during constant speed running can be, indeed, as high as 0.70 at high running speeds whereas in un-steady conditions (e.g. shuttle runs) the efficiency is much lower, approaching the values of muscle efficiency (0.25) when fast accelerations and decelerations are required; locomotion (apparent) efficiency is thus enhanced when tendon elastic recoil is maximized. Investigating the role of muscle and tendon behaviour during steady and non-steady state running could, therefore, provide important information about the underpinning mechanisms that determine the mechanical and energetic demands of human locomotion. For these reasons, this thesis focuses on two main topics (running at non-steady speeds and running at constant speed), each with its own specific aims.
Livres sur le sujet "Muscle mechanical work"
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Dissertations : On the mechanics of effervescence and fermentation and on the mechanics of the movement of the muscles. Philadelphia : American Philosophical Society, 1997.
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The matter of motion and Galvani's frogs. Bletchingdon : Rana, 2000.
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Biewener, Andrew A., et Shelia N. Patek, dir. Muscles and Skeletons. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198743156.003.0002.
Texte intégralRésumé :
Animal locomotion depends on the organization, physiology and biomechanical properties of muscles and skeletons. Musculoskeletal systems encompass the mechanical interactions of muscles and skeletal elements that ultimately transmit force for movement and support. Muscles not only perform work by contracting and shortening to generate force, they can also operate as brakes to slow the whole body or a single appendage. Muscles can also function as struts (rod-like) to maintain the position of a joint and facilitate elastic energy storage and recovery. Skeletal muscles share a basic organization and all rely on the same protein machinery for generating force and movement. Variation in muscle function, therefore, depends on the underlying mechanical and energetic components, enzymatic properties, and activation by the nervous system. Muscles require either an internal, external or hydrostatic skeletal system to transmit force for movement and support.
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Kreit, John W. Patient–Ventilator Interactions and Asynchrony. Sous la direction de John W. Kreit. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190670085.003.0011.
Texte intégralRésumé :
Patient–Ventilator Interactions and Asynchrony describes what happens when the patient and the ventilator do not work together in an effective, coordinated manner. Effective mechanical ventilation requires the synchronized function of two pumps: The mechanical ventilator is governed by the settings chosen by the clinician; the patient’s respiratory system is controlled by groups of neurons in the brain stem. Ideally, the ventilator simply augments and amplifies the activity of the respiratory system. Asynchrony between the ventilator and the patient reduces patient comfort, increases work of breathing, predisposes to respiratory muscle fatigue, and may even impair oxygenation and ventilation. The chapter describes the causes and consequences of patient–ventilator asynchrony during ventilator triggering and the inspiratory phase of the respiratory cycle and explains how to adjust ventilator settings to improve patient comfort and reduce the work of breathing.
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Pozio, Edoardo. Trichinellosis. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0068.
Texte intégralRésumé :
Trichinellosis is caused by nematodes of the genus Trichinella. These zoonotic parasites show a cosmopolitan distribution in all the continents, but Antarctica. They circulate in nature by synanthropic-domestic and sylvatic cycles. Today, eight species and four genotypes are recognized, all of which infect mammals, including humans, one species also infects birds, and two other species infect also reptiles.Parasites of the genus Trichinella are unusual among the other nematodes in that the worm undergoes a complete developmental cycle, from larva to adult to larva, in the body of a single host, which has a profound influence on the epidemiology of trichinellosis. When the cycle is complete, the muscles of the infected animal contain a reservoir of larvae, capable of long-term survival. Humans and other hosts become infected by ingesting muscle tissuescontaining viable larvae.The symptoms associated with trichinellosis vary with the severity of infection, i.e. the number of viable larvae ingested, and the time after infection. The capacity of the worm population to undergo massive multiplication in the body is a major determinant. Progression of disease follows the biological development of the parasite. Symptoms are associated first with the gastrointestinal tract, as the worms invade and establish in the small intestine, become more general as the body responds immunologically, and finally focus on the muscles as the larvae penetrate the muscle cells and develop there. Although Trichinella worms cause pathological changes directly by mechanical damage, most of the clinical features of trichinellosis are immunopathological in origin and can be related to the capacity of the parasite to induce allergic responses.The main source of human infection is raw or under-cooked meat products from pig, wild boar, bear, walrus, and horses, but meat products from other animals have been implicated. In humans, the diagnosis of infection is made by immunological tests or by direct examination of muscle biopsies using microscopy or by recovery of larvae after artificial digestion. Treatment requires both the use of anthelmintic drugs to kill the parasite itself and symptomatic treatment to minimize inflammatory responses.Both pre-slaughter prevention and post-slaughter control can be used to prevent Trichinella infections in animals. The first involves pig management control as well as continuous surveillance programmes. Meat inspection is a successful post-slaughter strategy. However, a continuous consumer education is of great importance in countries where meat inspection is not mandatory.
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(Editor), Stephen C. Cowin, et Jay D. Humphrey (Editor), dir. Cardiovascular Soft Tissue Mechanics. Springer, 2002.
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Cowin, Stephen C., et Jay D. Humphrey. Cardiovascular Soft Tissue Mechanics. Springer London, Limited, 2007.
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Northrup, Christiane, writer of supplementary textual content, dir. Diastasis recti : The whole-body solution to abdominal weakness and separation. 2016.
Trouver le texte intégralChapitres de livres sur le sujet "Muscle mechanical work"
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Patsute, Rajendra, Swati Pal Biswas, Nirdosh Rana et Gaur Ray. « Study of Postural Variation, Muscle Activity and Preferences of Monitor Placement in VDT Work ». Dans Lecture Notes in Mechanical Engineering, 447–62. India : Springer India, 2013. http://dx.doi.org/10.1007/978-81-322-1050-4_36.
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Chen, Jingtao, Peter Mitrouchev, Sabine Coquillart et Franck Quaine. « Magnitude Finger Forces Analysis During Simulating Pseudo-Haptic Spring ». Dans Lecture Notes in Mechanical Engineering, 215–20. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70566-4_34.
Texte intégralRésumé :
AbstractThis paper focuses on finger force magnitude analysis during stiffness discrimination task. In the frame of their Study and research work MS students from the Université Grenoble Alpes specially designed an experimental bench allowing to simulate a pseudo-haptic spring. Then, a series of stiffness discrimination tests between reals springs and a pseudo-haptic spring were performed. Finger pressing forces and students’ (subjects’) perception of spring stiffness were recorded and analyzed. The analysis of psychometric curves indicates that subjects underestimate the simulated stiffness of the pseudo-haptic spring. The results also indicate that the peak of finger force applied on pseudo-haptic spring increases as the simulated stiffness increases. Moreover, it was found that the relationships between the logarithm of stiffness and the finger force were linear for the real springs and the pseudo-haptic spring. Pseudo-haptics effect being provided by specially designed isometric force feedback device, the results of this study may be useful for computer-based rehabilitation tasks designed for motor disorder patients with muscle deficiency associated with limited joint movement range or for injured athletes in the process of rehabilitation.
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Varfolomeev, Sergey, Bella Grigorenko, Sofya Lushchekina, Patrick Masson, Galina Mahaeva et Alexander Nemuchin. « Human cholinesterases ». Dans ORGANOPHOSPHORUS NEUROTOXINS, 69–126. ru : Publishing Center RIOR, 2020. http://dx.doi.org/10.29039/21_069-126.
Texte intégralRésumé :
The work is devoted to modeling the elementary stages of the hydrolysis reaction in the active site of enzymes belonging to the class of cholinesterases — acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study allowed to describe at the molecular level the effect of the polymorphic modification of BChE, causing serious physiolog ical consequences. Cholinesterase plays a crucial role in the human body. AChE is one of the key enzymes of the central nervous system, and BChE performs protective functions in the body. According to the results of calculations using the combined method of quantum and molecular mechanics (KM/MM), the mechanism of the hydrolysis of the native acetylcholine substrate in the AChE active center was detailed. For a series of ester substrates, a method for estimation of dependence of the enzyme reactivity on the structure of the substrate has been developed. The mechanism of hydrolysis of the muscle relaxant of succininylcholine BChE and the effect of the Asp70Gly polymorph on it were studied. Using various computer simulation methods, the stability of the enzyme-substrate complex of two enzyme variants with succinylcholine was studied.
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Varfolomeev, Sergey, Bella Grigorenko, Sofya Lushchekina et Alexander Nemuchin. « Human cholinesterases ». Dans Organophosphorous Neurotoxins, 63–120. ru : Publishing Center RIOR, 2020. http://dx.doi.org/10.29039/chapter_5e4132b5f22366.15634219.
Texte intégralRésumé :
The work is devoted to modeling the elementary stages of the hydrolysis reaction in the active site of enzymes belonging to the class of cholinesterases — acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study allowed to describe at the molecular level the effect of the polymorphic modification of BChE, causing serious physiolog ical consequences. Cholinesterase plays a crucial role in the human body. AChE is one of the key enzymes of the central nervous system, and BChE performs protective functions in the body. According to the results of calculations using the combined method of quantum and molecular mechanics (KM/MM), the mechanism of the hydrolysis of the native acetylcholine substrate in the AChE active center was detailed. For a series of ester substrates, a method for estimation of dependence of the enzyme reactivity on the structure of the substrate has been developed. The mechanism of hydrolysis of the muscle relaxant of succininylcholine BChE and the effect of the Asp70Gly polymorph on it were studied. Using various computer simulation methods, the stability of the enzyme-substrate complex of two enzyme variants with succinylcholine was studied.
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F. Rodriguez, Ramón, Robert J. Aughey et François Billaut. « The Respiratory System during Intermittent-Sprint Work : Respiratory Muscle Work and the Critical Distribution of Oxygen ». Dans Respiratory Physiology. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.91207.
Texte intégralRésumé :
In healthy individuals at rest and while performing moderate-intensity exercise, systemic blood flow is distributed to tissues relative to their metabolic oxygen demands. During sustained high-intensity exercise, competition for oxygen delivery arises between locomotor and respiratory muscles, and the heightened metabolic work of breathing, therefore, contributes to limited skeletal muscle oxygenation and contractility. Intriguingly, this does not appear to be the case for intermittent-sprint work. This chapter presents new evidence, based on inspiratory muscle mechanical loading and hypoxic gas breathing, to support that the respiratory system of healthy men is capable of accommodating the oxygen needs of both locomotor and respiratory muscles when work is interspersed with short recovery periods. Only when moderate hypoxemia is induced, substantial oxygen competition arises in favour of the respiratory muscles. These findings extend our understanding of the relationship between mechanical and metabolic limits of varied exercise modes.
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Atherton, Philip J., et Nathaniel J. Szewczyk. « Regulation of Muscle Proteostasis via Extramuscular Signals ». Dans Extracellular and Intracellular Signaling, 77–104. The Royal Society of Chemistry, 2011. http://dx.doi.org/10.1039/bk9781849733434-00077.
Texte intégralRésumé :
Muscle protein synthesis and degradation are dynamic processes, the balance of which has been recently termed proteostasis. At any one time muscle has to balance outputs in synthesis and degradation from “inputs” of both extra- and intramuscular derived signals including those of hormones, autocrine/paracrine factors, metabolites, mechanical loading and attachment to the extracellular matrix. If there is a disturbance in whole-body/muscle homeostasis (i.e. due to illness, altered mechanical activity), the concentration of these inputs is altered. The resultant integration of these signaling inputs stimulates reprogramming of proteostasis. If the balance is tipped toward net synthesis or degradation muscles undergo hypertrophy or atrophy, respectively. The first aim of this chapter is to discuss what is currently known about how input signals, largely in isolation, regulate muscle protein turnover and encapsulates evidence from both animal and human work and both in vivo and in vitro studies. The second aim is to describe what is understood about the regulation of muscle proteostasis by extracellular-intracellular signaling with specific attention paid to the key regulators of proteostasis in healthy humans (i.e. responses to feeding, ambulation). The third aim is to discuss the regulation of muscle atrophy under pathological conditions of trauma, illness, disuse and aging.
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Brown, Andrew. « Heat and Lactic Acid ». Dans Bound by Muscle, 41—C4.N29. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197582633.003.0004.
Texte intégralRésumé :
Abstract Fletcher and Hopkins published the first accurate account of the generation of lactic acid during muscle contraction and its disappearance when oxygen is available during recovery. Langley set his new research student, Hill, to measure the heat produced during muscle activity to extend the earlier experiments. The tiny temperature changes that Hill recorded both during contraction and relaxation reflected the underlying chemical reactions. Meyerhof’s colleague, Weizsäcker, came to work in Hill’s laboratory and proved that oxygen is not necessary for the conversion of chemical energy into mechanical activity in muscle. Oxygen is necessary, however, for the removal of lactic acid. Hill predicted that about 20 percent of lactic acid is oxidized, while the majority is reconstituted into a precursor molecule. Another visitor, Jakob Parnas, disagreed and believed lactic acid was all burnt up. Meyerhof, in Kiel, described the unity of biochemical reactions between simple organisms such as yeast and animal cells.
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Magder, Sheldon. « Mechanical Limits of Cardiac Output at Maximal Aerobic Exercise ». Dans Exercise Physiology [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.103908.
Texte intégralRésumé :
This chapter uses an analytic approach to the factors limiting maximal aerobic exercise. A person’s maximal aerobic work is determined by their maximal oxygen consumption (VO2max). Cardiac output is the dominant determinant of VO2 and thus the primary determinant of population differences in VO2max. Furthermore, cardiac output is the product of heart rate and stroke volume and maximum heart rate is determined solely by a person’s age. Thus, maximum stroke volume is the major factor for physiological differences in aerobic performance. Stroke output must be matched by stroke volume return, which is determined by the mechanical properties of the systemic circulation. These are primarily the compliances of each vascular region and the resistances between them. I first discuss the physiological principles controlling cardiac output and venous return. Emphasis is placed on the importance of the distribution of blood flow between the parallel compliances of muscle and splanchnic beds as described by August Krogh in 1912. I then present observations from a computational modeling study on the mechanical factors that must change to reach known maximum cardiac outputs during aerobic exercise. A key element that comes out of the analysis is the role of the muscle pump in achieving high cardiac outputs.
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Joe, Seonggun, Federico Bernabei et Lucia Beccai. « A Review on Vacuum-Powered Fluidic Actuators in Soft Robotics ». Dans Rehabilitation of the Human Bone-Muscle System [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.104373.
Texte intégralRésumé :
In the past few years, vacuum-powered soft actuators have shown strong potential due to their promising mechanical performance (i.e., fail-safe, fast response, compactness, robustness, jamming, etc.). Indeed, they have been widely exploited in soft robots, for example, grippers and manipulators, wearable devices, locomotion robots, etc. In contrast to inflatable fluidic actuators, the properties of the materials with which they are built have a stronger influence on the kinematic trajectory. For this reason, understanding, both, the geometry and morphology of the core structure, and the material characteristics, is crucial to achieving the desired kinetics and kinematics. In this work, an overview of vacuum-powered soft fluidic actuators is provided, by classifying them as based on morphological design, origami architecture, and structural instability. A variety of constitutive materials and design principles are described and discussed. Strategies for designing vacuum-powered actuators are outlined from a mechanical perspective. Then the main materials and fabrication processes are described, and the most promising approaches are highlighted. Finally, the open challenges for enabling highly deformable and strong soft vacuum-powered actuation are discussed.
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Moreira, Isabella Cristina Pereira, Isabelle Rocha Arão, Helen Pereira dos Santos Soares, Karla Kellem de Lima, Ronaldo Rosa dos Santos Junior, Fernando Ernesto Ucker et Luana Machado dos Santos. « Evaluation of biomechanical variables in the task of laying the casing : a case study ». Dans METHODOLOGY FOCUSED ON THE AREA OF INTERDISCIPLINARITY- V1. Seven Editora, 2023. http://dx.doi.org/10.56238/methofocusinterv1-049.
Texte intégralRésumé :
The present work aims to analyze the numerous biomechanical variables observed during the execution of the laying task by a mason. For this, a research method based on the case study was developed, in which photographic records were made of the different stages that make up the activity. Such steps consist of loading of materials, preparation of the mortar, application of the mass on the wall, and laying of the ceramic piece. Biomechanical variables such as load lifting, repetitiveness, muscle contraction, mechanical compression, and inadequate posture were found. Through the analysis and discussion of the literature, measures were presented to be implemented in the worker's routine to minimize biomechanical risks, thus generating a safer and healthier work environment. Therefore, when the worker is in a favorable work environment, he is more productive. Investment in the ergonomic area within civil construction brings benefits, through productivity and minimization of expenses with occupational diseases and accidents at work.
Actes de conférences sur le sujet "Muscle mechanical work"
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Neptune, Richard R., Kotaro Sasaki et Steven A. Kautz. « Muscle Mechanical Work Adaptations With Increasing Walking Speed ». Dans ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176567.
Texte intégralRésumé :
Recent modeling studies of walking at self-selected speeds have identified how individual muscles work in synergy to satisfy the task demands including body support, forward propulsion and swing initiation (e.g. [1, 6]). These analyses revealed that young adults walking at a self-selected speed utilize a distribution of hip and knee extensor muscle force in early stance and ankle plantar flexor and rectus femoris force in late stance to provide support and forward propulsion [6]. However, how these muscles’ putative contributions to these functional tasks change with walking speed is not well understood. Intuitively, increasing walking speed would necessitate an increase in activity for muscles that contribute to forward propulsion. However, increasing walking speed is also associated with longer stride lengths (e.g., [2]), which may require increased activity from those muscles contributing to swing initiation, and increased activity from those muscles contributing to vertical support because the vertical excursion of the body’s center of mass increases.
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Karduna, Andrew R., et Phil W. McClure. « Moment Arm Calculations From In-Vivo Kinematic Data : Applications to the Trapezius Muscle ». Dans ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2527.
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Abstract Alterations in scapular movement patterns are believed to be associated with muscle weakness, fatigue, and paralysis. Due to the control that muscles exert on scapular position, it is important to understand their mechanical efficiency. Previous researchers have used the principle of virtual work to assess shoulder muscle moment arms, but these studies have focused on the glenohumeral joint [1,2]. The purpose of this investigation was to develop an approach for studying scapular muscle moment arms - specifically focusing on the middle and upper trapezius.
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Buchanan, Thomas S., Jian-Yu Cheng, Xiaofeng Shen et Kurt Manal. « An EMG-Driven Musculoskeletal Model for Estimation of Human Joint Moments During Isometric Time-Varying Loads ». Dans ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0176.
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Abstract The purpose of this work was to develop a robust EMG-driven elbow model to estimate muscle forces and joint torques of different people performing different time-varying loads at the elbow. The model consisted of an anatomical model, an EMG-to-activation model, a Hill-type muscle model, and a nonlinear optimizer. All of the major muscles about the elbow were taken into account. The parameters used by the muscle model were optimal fiber length, maximum contraction velocity, pennation angle, tendon slack length, and maximum muscle force. EMG and joint angle were input variables. Moment arm and muscle length varied as a function of joint angle, as defined in the anatomical model. The model was used to examine the importance of accounting for muscle velocity during rapid loads applied at fixed joint angles.
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Reddy, Aviktha, et Yahia M. Al-Smadi. « Inverse Dynamic Analysis of Shoulder Muscle Activity During Archery Draw Back ». Dans ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50881.
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The objective of this study is to conduct biomechanical simulation for a musculoskeletal of archery performance. The simulation aims to find the movement patterns in working postures, the muscle activity and joint reaction forces. The results obtained are discussed and the work presented can help analyze the utilization of various muscles during the performance of the repetitive motion of archery.
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Caruntu, Dumitru I., Ricardo Moreno et Robert Freeman. « Knee Muscle and Ligament Forces During Drop Landing Exercise ». Dans ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70982.
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This work investigates the human leg muscle and ligaments forces during a drop-landing exercise. An inverse dynamics 2-D model of human leg is used on this ballistic task in order to predict these forces. The model consists of three bony structures, namely femur, tibia, and patella. The joints of the model are the knee joint and the hip joint. The ligamentous structure of the knee includes the two cruciate ligaments, Anterior Cruciate Ligament (ACL) and the Posterior Cruciate Ligament (PCL), and the two collateral ligaments, Lateral Collateral Ligament (LCL) and Medial Collateral Ligament (MCL). The system of muscles of the system includes muscle such as quadriceps, hamstrings, gastrocnemius are included in the model. Experimental data used show a maximum of 100 degrees of flexion angle and ground reaction forces up to 4 times the body weight. The inverse dynamics 2-D model consists of an objective function to minimize the muscle forces, and a set of constraints consisting of equality constraints which are the dynamics equations of the bony structures, and inequality constraints in which all muscle forces must be positive. All muscle forces show a pattern in which they reach large magnitudes at the beginning of landing, decreasing as the subject end the exercise with a standing position.
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Hakansson, Nils A., et Maury L. Hull. « Influence of Pedaling Rate on Muscle Mechanical Energy in Low Power Recumbent Pedaling Using Forward Dynamic Simulations ». Dans ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35108.
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An understanding of the muscle power contributions to the crank and limb segments in recumbent pedaling would be useful in the development of rehabilitative pedaling exercises. The objectives of this work were to (i) develop a forward dynamic model to simulate low-power pedaling in the recumbent position, (ii) use the model to quantify the power contributions of the muscles to driving the crank and limb segments, and (iii) determine whether there were differences in the muscle power contributions required to simulate recumbent pedaling at three different pedaling rates. A forward dynamic model was used to determine the individual muscle excitation amplitude and timing to drive simulations that best replicated experimental kinematics and kinetics of recumbent pedaling. The segment kinematics, pedal reaction forces, and electromyograms (EMG) of 10 muscles of the right leg were recorded from 16 subjects as they pedaled a recumbent ergometer at 40, 50, and 60 rpm and a constant 50 W workrate. Intersegmental joint moments were computed using inverse dynamics and the muscle excitation onset and offset timing were determined from the EMG data. All quantities were averaged across ten cycles for each subject and averaged across subjects. The model-generated kinematic and kinetic quantities tracked almost always within 1 SD of the experimental data for all three pedaling rates. The uniarticular hip and knee extensors generated 65 percent of the total mechanical work in recumbent pedaling. The triceps surae muscles transferred power from the limb segments to the crank and the bi-articular muscles that crossed the hip and knee delivered power to the crank during the leg transitions between flexion and extension. The functions of the individual muscles did not change with pedaling rate, but the mechanical energy generated by the knee extensors and hip flexors decreased as pedaling rate increased. By varying the pedaling rate, it is possible to manipulate the individual muscle power contributions to the crank and limb segments in recumbent pedaling and thereby design rehabilitative pedaling exercises to meet specific objectives.
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Sandler, Reuben, et Stephen N. Robinovitch. « Impact Severity During a Fall Is Decreased by Lower Extremity Muscle Contractions During Descent ». Dans ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0084.
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Abstract Falls are a major cause of injury in the elderly, including the vast majority of hip and wrist fractures, and a considerable portion of vertebral fractures. In the event of a fall, one’s risk for such an injury depends on bone strength, and the configuration and kinetic energy (KE) of the body at the instant it contacts the ground. Consideration of acts such as sitting and squatting suggests that a major determinant of KE is the amount of energy “absorbed” (or negative work performed) during the descent phase of the fall by eccentrically-contracting lower extremity muscles. In the present study, we used a computational model of backwards falling to address the following questions: (1) what degree of impact energy attenuation might be achieved through muscle contraction during the descent phase of falling? and (2) what is the relative importance of muscle contractions at the hip, knee, and ankle in attenuating impact energy?
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Martinez-Villalpando, Ernesto C., Jeff Weber, Grant Elliott et Hugh Herr. « Biomimetic Prosthetic Knee Using Antagonistic Muscle-Like Activation ». Dans ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67705.
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The majority of commercial prosthetic knees are passive in nature and therefore cannot replicate the positive mechanical work exhibited by the natural human knee in early and late stance. In contrast to traditional purely dissipative prosthetic knees, we propose a biomimetic active agonist-antagonist structure designed to reproduce both positive and negative work phases of the natural joint while using series elasticity to minimize net energy consumption. We present the design and implementation of the active knee prosthesis prototype.
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Danley, Bryan B., et Shadow Huang. « Biomechanical and Biochemical Study of Muscle-Tendon-Bone in Porcine Digital Flexor Tendon ». Dans ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52360.
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The musculoskeletal system provides the body with both movement and support. In particular, contractile forces developed in the muscles are transmitted through the muscle-tendon junction (MTJ) into the tendon and then through the tendon-bone insertion into the bone. Each junction occurs between two dissimilar materials (muscle-to-tendon and tendon-to-bone) and neither is fully understood. The current study analyzes the relationship between the tissue microstructure and macro-scale biomechanical properties of the muscle-tendon-bone unit to better understand the anisotropic mechanical behavior of the tissue. Collagen content was assayed at various locations along the porcine digital flexor tendon. Collagen concentration as a percent of the wet weight in the bone end was found to be 20.4±5.2% (n=6), the mid tendon to be 20.6±5.3% (n=6), and the muscle end to be 25.2±3.6% (n=4). No statistical differences were found between these collagen concentrations. Additionally, to the best of the authors’ knowledge, this is the first study to report cross-sectional stress-strain data for the muscle-tendon-bone unit. Results indicate that the tendon cross-sectional stiffness increases from the proximal end to the distal end. However, no direction dependent anisotropies were found between the mediolateral and dorsopalmar directions. Effects of microstructural components, such as glycosaminoglycans and collagen, and phenomenon such as fibril sliding and cross-linking, are discussed in relation to the reported cross-section stress-strain response. This work provides a synergistic approach for quantifying biomechanical and biochemical properties of biological tissue, and potentially facilitates the development of tissue engineered MTJ and tendon-bone insertion.
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Flemming, Leslie, et Stephen Mascaro. « Wet SMA Actuator Array With Matrix Vasoconstriction Device ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82952.
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A new mechanism for controlling arrays of Shape Memory Alloy (SMA) muscle wires has been developed. Similar to previous work, SMA wires on the order of 0.25 mm in diameter are embedded in a network of compliant fluid filled vessels on the order of 1 mm in diameter. Hot and cold water are delivered through the vascular network to convectively heat and cool the SMA muscles, causing them to contract and extend. By arranging the muscles or actuators in a 2D array, n2 actuators can be controlled using 2n valves, where the valves control the flow to and from rows and columns of actuators. However, unlike the previous Matrix Manifold and Valve system (MMV), the fluid flows to the actuators are now controlled using a Matrix Vasoconstriction Device (MVD). The MVD is capable of constricting combinations of the vessels, which are arranged in rows and columns. The MVD does not introduce any fluidic resistance to the network until constricted, allowing for larger flow rates and faster muscle cycling. The MVD system architecture also removes undesired dynamic effects stemming from fluidic capacitance which were suffered by the MMV. An array of 16 muscle wires has been experimentally implemented using an MVD with 8 control inputs. The MVD has been constructed in a 50 mm × 50 mm × 60 mm volume, and the overall length of the actuators is 500 mm. The system will drive each SMA wire at a rate of 2 Hz with a force of 10 N and a stroke of 10 mm. The system could control a robotic hand with up to 16 DOF and fit within the size of a human forearm.