Articles de revues : « Muscle and tendon »

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Avey, Alec M., et Keith Baar. « Muscle-tendon cross talk during muscle wasting ». American Journal of Physiology-Cell Physiology 321, n^o 3 (1 septembre 2021) : C559—C568. http://dx.doi.org/10.1152/ajpcell.00260.2021.

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In organisms from flies to mammals, the initial formation of a functional tendon is completely dependent on chemical signals from muscles (myokines). However, how myokines affect the maturation, maintenance, and regeneration of tendons as a function of age is completely unstudied. Here we discuss the role of four myokines—fibroblast growth factors (FGF), myostatin, the secreted protein acidic and rich in cysteine (SPARC) miR-29—in tendon development and hypothesize a role for these factors in the progressive changes in tendon structure and function as a result of muscle wasting (disuse, aging, and disease). Because of the close relationship between mechanical loading and muscle and tendon regulation, disentangling muscle-tendon cross talk from simple mechanical loading is experimentally quite difficult. Therefore, we propose an experimental framework that hopefully will be useful in demonstrating muscle-tendon cross talk in vivo. Though understudied, the promise of a better understanding of muscle-tendon cross talk is the development of new interventions that will improve tendon development, regeneration, and function throughout the lifespan.

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Kardon, G. « Muscle and tendon morphogenesis in the avian hind limb ». Development 125, n^o 20 (15 octobre 1998) : 4019–32. http://dx.doi.org/10.1242/dev.125.20.4019.

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The proper development of the musculoskeletal system in the tetrapod limb requires the coordinated development of muscle, tendon and cartilage. This paper examines the morphogenesis of muscle and tendon in the developing avian hind limb. Based on a developmental series of embryos labeled with myosin and tenascin antibodies in whole mount, an integrative description of the temporal sequence and spatial pattern of muscle and tendon morphogenesis and their relationship to cartilage throughout the chick hind limb is presented for the first time. Anatomically distinct muscles arise by the progressive segregation of muscle: differentiated myotubes first appear as a pair of dorsal and ventral muscle masses; these masses subdivide into dorsal and ventral thigh, shank and foot muscle masses; and finally these six masses segregate into individual muscles. From their initial appearance, most myotubes are precisely oriented and their pattern presages the pattern of future, individual muscles. Anatomically distinct tendons emerge from three tendon primordia associated with the major joints of the limb. Contrary to previous reports, comparison of muscle and tendon reveals that much of their morphogenesis is temporally and spatially closely associated. To test whether reciprocal muscle-tendon interactions are necessary for correct muscle-tendon patterning or whether morphogenesis of each of these tissues is autonomous, two sets of experiments were conducted: (1) tendon development was examined in muscleless limbs produced by coelomic grafting of early limb buds and (2) muscle development was analyzed in limbs where tendon had been surgically altered. These experiments demonstrate that in the avian hind limb the initial morphogenetic events, formation of tendon primordia and initial differentiation of myogenic precursors, occur autonomously with respect to one another. However, later morphogenetic events, such as subdivision of muscle masses and segregation of tendon primordia into individual tendons, do require to various degrees reciprocal interactions between muscle and tendon. The dependence of these later morphogenetic events on tissue interactions differs between different proximodistal regions of the limb.

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Konow, Nicolai, Emanuel Azizi et Thomas J. Roberts. « Muscle power attenuation by tendon during energy dissipation ». Proceedings of the Royal Society B : Biological Sciences 279, n^o 1731 (28 septembre 2011) : 1108–13. http://dx.doi.org/10.1098/rspb.2011.1435.

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An important function of skeletal muscle is deceleration via active muscle fascicle lengthening, which dissipates movement energy. The mechanical interplay between muscle contraction and tendon elasticity is critical when muscles produce energy. However, the role of tendon elasticity during muscular energy dissipation remains unknown. We tested the hypothesis that tendon elasticity functions as a mechanical buffer, preventing high (and probably damaging) velocities and powers during active muscle fascicle lengthening. We directly measured lateral gastrocnemius muscle force and length in wild turkeys during controlled landings requiring rapid energy dissipation. Muscle-tendon unit (MTU) strain was measured via video kinematics, independent of muscle fascicle strain (measured via sonomicrometry). We found that rapid MTU lengthening immediately following impact involved little or no muscle fascicle lengthening. Therefore, joint flexion had to be accommodated by tendon stretch. After the early contact period, muscle fascicles lengthened and absorbed energy. This late lengthening occurred after most of the joint flexion, and was thus mainly driven by tendon recoil. Temporary tendon energy storage led to a significant reduction in muscle fascicle lengthening velocity and the rate of energy absorption. We conclude that tendons function as power attenuators that probably protect muscles against damage from rapid and forceful lengthening during energy dissipation.

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Harșa, Mihai-Iuliu, Loránd Kocsis, Angéla-Mária Czundel, Lóránd Dénes et Zsuzsanna Pap. « Anatomical Variations of the Peroneus Tertius and Extensor Digitorum Longus Muscles – Case Presentation ». Journal of Interdisciplinary Medicine 6, n^o 3 (1 septembre 2021) : 162–66. http://dx.doi.org/10.2478/jim-2021-0025.

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Abstract Introduction: The extensor digitorum longus and peroneus tertius muscles have multiple morphological variations. The tendinous slips of these muscles are used as grafts to replace other damaged tendons. Case presentation: We present a unique anatomical variant observed during dissection of a cadaver at the Department of Anatomy and Embryology of the “George Emil Palade” University of Medicine, Pharmacy, Science and Technology of Târgu Mureș, Romania. The peroneus tertius muscle was identified on the left lower extremity as originating from the inferior third of the fibula and interosseus membrane. The posterior belly of this muscle joins the muscular belly of the extensor digitorum longus muscle. The tendons of toes II to V detach from the extensor digitorum longus muscle with an additional tendon. This last tendon gives off an accessory tendinous slip; lateral to this, the peroneus tertius muscle tendon is observed. In case of the right lower limb we also noted the peroneus tertius muscle originating from the distal part of the extensor digitorum longus muscle. Regarding the extensor digitorum longus muscle we describe an accessory tendinous slip. Conclusion: The anatomical variation reported in this study is similar to those reported by previous studies, but displays particular characteristics regarding the VI tendon of extensor digitorum longus and the joining of the peroneus tertius and extensor digitorum longus muscles in the left lower extremity.

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Kagan, I. I., V. V. Ivlev et A. M. Gur'yanov. « Differences and regularities of the macro- and microscopic structure of the limb tendons ». Journal of Anatomy and Histopathology 11, n^o 1 (30 mars 2022) : 36–43. http://dx.doi.org/10.18499/2225-7357-2022-11-1-36-43.

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The aim of the study was to present differences and regularities in the macro- and microscopic structure of the muscle tendons of the limbs identified by comparative analysis and generalization of the obtained findings.Material and methods. The study included transverse histotopograms of 519 tendons of 17 different muscles of the upper and lower limbs. Histotopograms were received from 93 human cadavers and amputated limbs of 10 patients. Transverse sections of tendons up to 20 μm thick were stained with picrofuchsin according to Van Gieson, and hematoxylin–eosin. Histotopograms were studied and photographed using a stereoscopic microscope MBS-10.Results. The authors have generalized data on the macro- and microscopic structure of the limb tendons. General regularities of the internal macro- and microscopic structure of the tendons have been specified. It has been demonstrated that these regularities are of applied relevance for improvement of restorative tendon microsurgery. Individual differences and differences between the tendons of different muscles at the structural level were revealed: the number, size, architectonics of the tendon bundles of the 1st order. Tendon bundles of the 1st order are the main structural units of the macro- and microscopic structure of the limb muscle tendons. Depending on the size of the cross-sectional area, they can be divided into small (0.004–0.009 mm2), medium (0.01–0.04 mm2), large (0.05–0.09 mm2) and very large (0.1–0.5 mm2). There were detected differences in the number, ratio and architectonics of the tendon bundles at different levels within one tendon; this allows assuming division and fusion of tendon bundles of the 1st order throughout the tendon.Conclusion. The macro- and microscopic structure of the muscle tendons of the upper and lower limbs demonstrates general regularities and differences in the structure of the various muscle tendons, the fact being of theoretical and applied significance.

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Strumpf, Dan, et Talila Volk. « Kakapo, a Novel Cytoskeletal-associated Protein Is Essential for the Restricted Localization of the Neuregulin-like Factor, Vein, at the Muscle–Tendon Junction Site ». Journal of Cell Biology 143, n^o 5 (30 novembre 1998) : 1259–70. http://dx.doi.org/10.1083/jcb.143.5.1259.

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In the Drosophila embryo, the correct association of muscles with their specific tendon cells is achieved through reciprocal interactions between these two distinct cell types. Tendon cell differentiation is initiated by activation of the EGF-receptor signaling pathway within these cells by Vein, a neuregulin-like factor secreted by the approaching myotube. Here, we describe the cloning and the molecular and genetic analyses of kakapo, a Drosophila gene, expressed in the tendons, that is essential for muscle-dependent tendon cell differentiation. Kakapo is a large intracellular protein and contains structural domains also found in cytoskeletal-related vertebrate proteins (including plakin, dystrophin, and Gas2 family members). kakapo mutant embryos exhibit abnormal muscle-dependent tendon cell differentiation. A major defect in the kakapo mutant tendon cells is the failure of Vein to be localized at the muscle–tendon junctional site; instead, Vein is dispersed and its levels are reduced. This may lead to aberrant differentiation of tendon cells and consequently to the kakapo mutant deranged somatic muscle phenotype.

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Biewener, A., et R. Baudinette. « In vivo muscle force and elastic energy storage during steady-speed hopping of tammar wallabies (Macropus eugenii) ». Journal of Experimental Biology 198, n^o 9 (1 septembre 1995) : 1829–41. http://dx.doi.org/10.1242/jeb.198.9.1829.

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In order to evaluate the role of elastic energy recovery in the hopping of macropodids, in vivo measurements of muscletendon forces using buckle force transducers attached to the tendons of the gastrocnemius (G), plantaris (PL) and flexor digitorum longus (FDL) of tammar wallabies were made as the animals hopped on a treadmill at speeds ranging from 2.1 to 6.3 m s-1. These muscles and tendons constitute the main structures that are most important in energy storage and recovery. Electromyographic recordings from the lateral gastrocnemius and plantaris muscles, together with high-speed films (200 frames s-1) and video (60 fields s-1), were also used to correlate muscle activation and kinematic patterns of limb movement with force development. On the basis of in situ calibrations of the buckle transducers, we found that muscle forces and elastic energy storage increased with increased hopping speed in all three muscletendon units. Elastic energy recovery reached a maximum of 25 % of metabolic energy expenditure at 6.3 m s-1 and is probably greater than this at higher speeds. Force sharing among the three muscles was consistently maintained over this range of speeds in terms of recruitment. Although forces and stresses were generally comparable within the gastrocnemius and plantaris muscles, maximal tendon stresses were considerably greater in the gastrocnemius, because of its smaller cross-sectional area (peak muscle stress: 227 versus 262 kPa; peak tendon stress: 36 versus 32 MPa, G versus PL). As a result, energy storage was greatest in the gastrocnemius tendon despite its much shorter length, which limits its volume and, hence, energy storage capacity, compared with PL and FDL tendons. Forces and stresses (17 MPa maximum) developed within the FDL tendon were consistently much lower than those for the other two tendons. Peak stresses in these three tendons indicated safety factors of 3.0 for G, 3.3 for PL and 6.0 for FDL. The lower stresses developed within the tendons of the plantaris and, especially, the flexor digitorum longus may indicate the need to maintain sufficient stiffness for phalangeal control of foot placement, at the expense of reduced strain energy recovery.

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Stevic, Ruza, et Dragan Masulovic. « Ultrasound diagnostics of muscle and tendon injuries ». Srpski arhiv za celokupno lekarstvo 137, n^o 11-12 (2009) : 647–52. http://dx.doi.org/10.2298/sarh0912647s.

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Introduction. Sonography is a useful technique for the investigation of a number of musculoskeletal disorders. The most common indication for ultrasonography of muscles and tendons is the diagnosis of traumatic lesions, distinguishing them from other disorders and follow-up of healing process. Objective. The purpose of this paper is to show the importance of ultrasound in the diagnosis of muscle and tendon injuries. Methods. The study included 170 patients (148 male and 22 female), mean age 29.6 years (range 14-60 years). All examinations were performed by linear transducer of 7.5-10 MHz, with longitudinal and transverse scanning. Ultrasound examination followed physical examination. Results. Traumatic lesions of muscles were diagnosed in 113 patients (66.7%) and tendon injuries in 57 cases (33.2%). The muscle changes detected by ultrasonography were the following: 70 (61.9%) partial and two (1.76%) complete ruptures, 22 (19.46%) haematoma, 9 (7.96%) strains grade I, 4 fibroses and 4 ossifying myositis 4 (3.5%, respectively). Complications of muscle injuries were diagnosed in two cases, a muscular hernia and an arteriovenous fistula. Among tendon injuries, 21 (33.8%) ruptures and 36 (66.1%) tendinitis were diagnosed. Accompanying effusion in the bursa of patients with tendon injuries was found in 9 cases. Conclusion. Ultrasonography allowed visualization and objective assessment of the type and the extent of traumatic pathomorphological changes of muscles and tendons. Such diagnostic possibilities of ultrasonography are especially important in the choice of appropriate therapy.

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Maas, Huub, Wendy Noort, Hiltsje A. Smilde, Jacob A. Vincent, Paul Nardelli et Timothy C. Cope. « Detection of epimuscular myofascial forces by Golgi tendon organs ». Experimental Brain Research 240, n^o 1 (22 octobre 2021) : 147–58. http://dx.doi.org/10.1007/s00221-021-06242-1.

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AbstractSkeletal muscles embed multiple tendon organs, both at the proximal and distal ends of muscle fibers. One of the functions of such spatial distribution may be to provide locally unique force feedback, which may become more important when stresses are distributed non-uniformly within the muscle. Forces exerted by connections between adjacent muscles (i.e. epimuscular myofascial forces) may cause such local differences in force. The aim of this exploratory study was to investigate the effects of mechanical interactions between adjacent muscles on sensory encoding by tendon organs. Action potentials from single afferents were recorded intra-axonally in response to ramp-hold release (RHR) stretches of a passive agonistic muscle at different lengths or relative positions of its passive synergist. The tendons of gastrocnemius (GAS), plantaris (PL) and soleus (SO) muscles were cut from the skeleton for attachment to servomotors. Connective tissues among these muscles were kept intact. Lengthening GAS + PL decreased the force threshold of SO tendon organs (p = 0.035). The force threshold of lateral gastrocnemius (LG) tendon organs was not affected by SO length (p = 0.371). Also displacing LG + PL, kept at a constant muscle–tendon unit length, from a proximal to a more distal position resulted in a decrease in force threshold of LG tendon organs (p = 0.007). These results indicate that tendon organ firing is affected by changes in length and/or relative position of adjacent synergistic muscles. We conclude that tendon organs can provide the central nervous system with information about local stresses caused by epimuscular myofascial forces.

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Pollock, C. M., et R. E. Shadwick. « Allometry of muscle, tendon, and elastic energy storage capacity in mammals ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 266, n^o 3 (1 mars 1994) : R1022—R1031. http://dx.doi.org/10.1152/ajpregu.1994.266.3.r1022.

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This paper considers the structural properties of muscle-tendon units in the hindlimbs of mammals as a function of body mass. Morphometric analysis of the ankle extensors, digital flexors, and digital extensors from 35 quadrupedal species, ranging in body mass from 0.04 to 545 kg, was carried out. Tendon dimensions scale nearly isometrically, as does muscle mass. The negative allometry of muscle fiber length results in positive allometric scaling of muscle cross-sectional areas in all but digital extensors. Maximum muscle forces are predicted to increase allometrically, with mass exponents as high as 0.91 in the plantaris, but nearly isometrically (0.69) in the digital extensors. Thus the maximum amount of stress a tendon may experience in vivo, as indicated by the ratio of muscle and tendon cross-sectional areas, increases with body mass in digital flexors and ankle extensors. Consequently, the capacity for elastic energy storage scales with positive allometry in these tendons but is isometric in the digital extensors, which probably do not function as springs in normal locomotion. These results suggest that the springlike tendons of large mammals can potentially store more elastic strain energy than those of smaller mammals because their disproportionately stronger muscles can impose higher tendon stresses.

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Ward, Samuel R., Gregory J. Loren, Scott Lundberg et Richard L. Lieber. « High Stiffness of Human Digital Flexor Tendons Is Suited for Precise Finger Positional Control ». Journal of Neurophysiology 96, n^o 5 (novembre 2006) : 2815–18. http://dx.doi.org/10.1152/jn.00284.2006.

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The objective of this study was to define the biomechanical properties of the human digital flexor tendons and to compare these biomechanical properties to other muscle-tendon units in the forearm. Mechanical measurements were performed on fresh-frozen tendons under physiological load and temperature conditions. Loads were determined by first measuring the physiological cross-sectional area of each digital belly of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) and estimating maximum tension ( Po) of that specific muscle head. Loading each tendon to the appropriate Po resulted in no significant difference in tendon strain among any of the tendons within each muscle ( P > 0.05; digits 2–5) or between muscle types (FDP vs. FDS). The one exception to this finding was that a significantly higher strain at Po was observed in the FDP tendon to the small finger ( P < 0.05). Average absolute strains observed for the FDP and FDS tendons (1.20 ± 0.38%, mean ± SD; n = 39) were significantly lower than those observed previously in a study of the prime movers of the wrist. The measured strain of ∼1.5% was less than half of that predicted to occur in muscles of this architectural design. Modeling sarcomere shortening magnitudes during FDP or FDS contraction yielded a value of only 0.10 μm, which would have a negligible effect on the force generating capacity of these muscles. Thus the high stiffness of the digital flexor tendons suits them well for fine positional control and would render their muscle spindles quite sensitive to length perturbations at the fingertips.

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Vertullo, Christopher J., Jason M. Konrath, Benjamin Kennedy, Hamish Bush, Rodney S. Barrett et David G. Lloyd. « HAMSTRING MORPHOLOGY AND STRENGTH REMAIN ALTERED 2 YEARS FOLLOWING A HAMSTRING GRAFT IN ACL RECONSTRUCTION ». Orthopaedic Journal of Sports Medicine 5, n^o 5_suppl5 (1 mai 2017) : 2325967117S0018. http://dx.doi.org/10.1177/2325967117s00181.

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Background: The hamstring graft used in anterior cruciate ligament (ACL) reconstruction has been shown to lead to changes to the semitendinosus and gracilis musculature. This study further evaluated the effect of the surgery on hamstring muscle morphology and knee muscle strength at 2 years post-surgery. Hypotheses: (1) Loss of donor muscle size would significantly correlate with knee muscle strength deficits (2) Loss of donor muscle size would be greater for muscles that do not experience tendon regeneration, and (3) Morphological adaptations would also be evident in non-donor knee muscles. Study Design: Cross sectional evaluation. Methods: 20 participants (14 male, 6 female, 29 ± 7 years, 82 ± 15 kg) that had undergone a hamstring graft in ACL reconstruction at least two years previously, underwent bilateral MRI and subsequent strength testing. Muscle and tendon volumes, peak CSA’s and lengths were determined for 12 muscles and 6 functional muscle groups of the surgical and contralateral limbs. Peak isokinetic concentric strength was measured in knee flexion/extension and internal/external tibial rotation. Results: Only 50% of the patients regenerated both the semitendinosus and gracilis tendons. The regenerated tendons were longer with larger volume and CSA compared to the contralateral side. Deficits in semitendinosus and gracilis muscle size were greater for tendons that did not regenerate. In addition, combined hamstrings (semitendinosus, semimembranosus, biceps femoris) and combined medial knee muscles (semitendinosus, semimembranosus, gracilis, vastus medialis, medial gastrocnemius, sartorius) on the surgical side were reduced in volume by 12% and 10% respectively. A 7% larger volume was observed in the surgical leg for the biceps femoris and corresponded with a lower internal/external tibial rotation strength ratio. The difference in volume, peak CSA and length of the semitendinosus and gracilis correlated significantly with the deficit in knee flexion strength with Pearson correlations of 0.51, 0.57 and 0.61 respectively. Conclusion: The muscle-tendon properties of the semitendinosus and gracilis are substantially altered following harvesting, and these alterations may contribute to knee flexor weakness in the surgical limb. These deficits are more pronounced in tendons that do not regenerate and are only partially offset by compensatory hypertrophy of other hamstring muscles. Clinical Relevance: Surgeons should consider muscle retraction of the hamstring following tendon harvest in their choice of graft option for ACL reconstruction.

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Fukutani, Atsuki, et Toshiyuki Kurihara. « Tendon Cross-Sectional Area is Not Associated with Muscle Volume ». Journal of Applied Biomechanics 31, n^o 3 (juin 2015) : 176–80. http://dx.doi.org/10.1123/jab.2014-0183.

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Recent studies have reported that resistance training increases the cross-sectional areas (CSAs) of tendons; however, this finding has not been consistently observed across different studies. If tendon CSA increases through resistance training, resistance-trained individuals should have larger tendon CSAs as compared with untrained individuals. Therefore, in the current study, we aimed to investigate whether resistance training increases tendon CSAs by comparing resistance-trained and untrained individuals. Sixteen males, who were either body builders or rugby players, were recruited as the training group, and 11 males, who did not participate in regular resistance training, were recruited into the control group. Tendon CSAs and muscle volumes of the triceps brachii, quadriceps femoris, and triceps surae were calculated from images obtained by using magnetic resonance imaging. The volumes of the 3 muscles were significantly higher in the training group than in the control group (P < .001 for all muscles). However, a significant difference in tendon CSAs was found only for the distal portion of the triceps surae tendon (P = .041). These findings indicate that tendon CSA is not associated with muscle volume, suggesting that resistance training does not increase tendon CSA.

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Ito, Ko, Yasuhiro Go, Shoji Tatsumoto, Chika Usui, Yosuke Mizuno, Eiji Ikami, Yuta Isozaki et al. « Gene expression profiling of the masticatory muscle tendons and Achilles tendons under tensile strain in the Japanese macaque Macaca fuscata ». PLOS ONE 18, n^o 1 (19 janvier 2023) : e0280649. http://dx.doi.org/10.1371/journal.pone.0280649.

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Both Achilles and masticatory muscle tendons are large load-bearing structures, and excessive mechanical loading leads to hypertrophic changes in these tendons. In the maxillofacial region, hyperplasia of the masticatory muscle tendons and aponeurosis affect muscle extensibility resulting in limited mouth opening. Although gene expression profiles of Achilles and patellar tendons under mechanical strain are well investigated in rodents, the gene expression profile of the masticatory muscle tendons remains unexplored. Herein, we examined the gene expression pattern of masticatory muscle tendons and compared it with that of Achilles tendons under tensile strain conditions in the Japanese macaque Macaca fuscata. Primary tenocytes isolated from the masticatory muscle tendons (temporal tendon and masseter aponeurosis) and Achilles tendons were mechanically loaded using the tensile force and gene expression was analyzed using the next-generation sequencing. In tendons exposed to tensile strain, we identified 1076 differentially expressed genes with a false discovery rate (FDR) < 10−10. To identify genes that are differentially expressed in temporal tendon and masseter aponeurosis, an FDR of < 10−10 was used, whereas the FDR for Achilles tendons was set at > 0.05. Results showed that 147 genes are differentially expressed between temporal tendons and masseter aponeurosis, out of which, 125 human orthologs were identified using the Ensemble database. Eight of these orthologs were related to tendons and among them the expression of the glycoprotein nmb and sphingosine kinase 1 was increased in temporal tendons and masseter aponeurosis following exposure to tensile strain. Moreover, the expression of tubulin beta 3 class III, which promotes cell cycle progression, and septin 9, which promotes cytoskeletal rearrangements, were decreased in stretched Achilles tendon cells and their expression was increased in stretched masseter aponeurosis and temporal tendon cells. In conclusion, cyclic strain differentially affects gene expression in Achilles tendons and tendons of the masticatory muscles.

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Boutin, Robert, et Russell Fritz. « Musculotendinous Disorders in the Upper Extremity : Part 2. MRI of the Elbow, Forearm, Wrist, and Hand ». Seminars in Musculoskeletal Radiology 21, n^o 04 (3 août 2017) : 376–91. http://dx.doi.org/10.1055/s-0037-1604008.

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AbstractMuscle and tendon injuries about the elbow and more distal aspect of the upper arm are commonly evaluated and characterized with magnetic resonance imaging. This article reviews our experience with muscle and tendon injury as well as denervation of muscles. We focus on abnormalities of the biceps and the triceps tendons about the elbow as well as abnormalities of the flexor and extensor tendons about the elbow, forearm, wrist, and hand. We also discuss and illustrate our experience with lacerations, crush injuries, and muscle hernias in the forearm.

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Wilson, Alan, et Glen Lichtwark. « The anatomical arrangement of muscle and tendon enhances limb versatility and locomotor performance ». Philosophical Transactions of the Royal Society B : Biological Sciences 366, n^o 1570 (27 mai 2011) : 1540–53. http://dx.doi.org/10.1098/rstb.2010.0361.

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The arrangement of muscles and tendons has been studied in detail by anatomists, surgeons and biomechanists for over a century, and the energetics and mechanics of muscle contraction for almost as long. Investigation of how muscles function during locomotion and the relative length change in muscle fibres and the associated elastic tendon has, however, been more challenging. In recent years, novel in vivo measurement methods such as ultrasound and sonomicrometry have contributed to our understanding of the dynamics of the muscle tendon unit during locomotion. Here, we examine both published and new data to explore how muscles are arranged to deliver the wide repertoire of locomotor function and the trade-offs between performance and economy that result.

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Yan, Ruojin, Hong Zhang, Yuanzhu Ma, Ruifu Lin, Bo Zhou, Tao Zhang, Chunmei Fan et al. « Discovery of Muscle-Tendon Progenitor Subpopulation in Human Myotendinous Junction at Single-Cell Resolution ». Research 2022 (29 septembre 2022) : 1–16. http://dx.doi.org/10.34133/2022/9760390.

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The myotendinous junction (MTJ) is a complex and special anatomical area that connects muscles and tendons, and it is also the key to repairing tendons. Nevertheless, the anatomical structure and connection structure of MTJ, the cluster and distribution of cells, and which cells are involved in repairing the tissue are still unclear. Here, we analyzed the cell subtype distribution and function of human MTJ at single-cell level. We identified four main subtypes, including stem cell, muscle, tendon, and muscle-tendon progenitor cells (MTP). The MTP subpopulation, which remains the characteristics of stem cells and also expresses muscle and tendon marker genes simultaneously, may have the potential for bidirectional differentiation. We also found the muscle-tendon progenitor cells were distributed in the shape of a transparent goblet; muscle cells first connect to the MTP and then to the tendon. And after being transplanted in the MTJ injury model, MTP exhibited strong regenerative capability. Finally, we also demonstrated the importance of mTOR signaling for MTP maintenance by in vitro addition of rapamycin and in vivo validation using mTOR-ko mice. Our research conducted a comprehensive analysis of the heterogeneity of myotendinous junction, discovered a special cluster called MTP, provided new insights into the biological significance of myotendinous junction, and laid the foundation for future research on myotendinous junction regeneration and restoration.

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Loram, Ian D., Martin Lakie, Irene Di Giulio et Constantinos N. Maganaris. « The Consequences of Short-Range Stiffness and Fluctuating Muscle Activity for Proprioception of Postural Joint Rotations : The Relevance to Human Standing ». Journal of Neurophysiology 102, n^o 1 (juillet 2009) : 460–74. http://dx.doi.org/10.1152/jn.00007.2009.

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Proprioception comes from muscles and tendons. Tendon compliance, muscle stiffness, and fluctuating activity complicate transduction of joint rotation to a proprioceptive signal. These problems are acute in postural regulation because of tiny joint rotations and substantial short-range muscle stiffness. When studying locomotion or perturbed balance these problems are less applicable. We recently measured short-range stiffness in standing and considered the implications for load stability. Here, using an appropriately simplified model we analyze the conversion of joint rotation to spindle input and tendon tension while considering the effect of short-range stiffness, tendon compliance, fluctuating muscle activity, and fusimotor activity. Basic principles determine that when muscle stiffness and tendon compliance are high, fluctuating muscle activity is the greatest factor confounding registration of postural movements, such as ankle rotations during standing. Passive and isoactive muscle, uncomplicated by active length fluctuations, enable much better registration of joint rotation and require fewer spindles. Short-range muscle stiffness is a degrading factor for spindle input and enhancing factor for Golgi input. Constant fusimotor activity does not enhance spindle registration of postural joint rotations in actively modulated muscle: spindle input remains more strongly associated with muscle activity than joint rotation. A hypothesized rigid α–γ linkage could remove this association with activity but would require large numbers of spindles in active postural muscles. Using microneurography, the existence of a rigid α–γ linkage could be identified from the correlation between spindle output and muscle activity. Basic principles predict a proprioceptive “dead zone” in the active agonist muscle that is related to the short-range muscle stiffness.

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Carter, Stephen J., Laura Q. Rogers, Heather R. Bowles et Gary R. Hunter. « Muscle-tendon Elasticity ». Medicine & ; Science in Sports & ; Exercise 50, n^o 5S (mai 2018) : 834. http://dx.doi.org/10.1249/01.mss.0000538746.81701.67.

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Vila Pouca, Maria C. P., Marco P. L. Parente, Renato M. Natal Jorge et James A. Ashton-Miller. « Injuries in Muscle-Tendon-Bone Units : A Systematic Review Considering the Role of Passive Tissue Fatigue ». Orthopaedic Journal of Sports Medicine 9, n^o 8 (1 août 2021) : 232596712110207. http://dx.doi.org/10.1177/23259671211020731.

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Background: Low-cycle fatigue damage accumulating to the point of structural failure has been recently reported at the origin of the human anterior cruciate ligament under strenuous repetitive loading. If this can occur in a ligament, low-cycle fatigue damage may also occur in the connective tissue of muscle-tendon units. To this end, we reviewed what is known about how, when, and where injuries of muscle-tendon units occur throughout the body. Purpose: To systematically review injuries in the muscle-tendon-bone complex; assess the site of injury (muscle belly, musculotendinous junction [MTJ], tendon/aponeurosis, tendon/aponeurosis–bone junction, and tendon/aponeurosis avulsion), incidence, muscles and tendons involved, mechanism of injury, and main symptoms; and consider the hypothesis that injury may often be consistent with the accumulation of multiscale material fatigue damage during repetitive submaximal loading regimens. Methods: PubMed, Web of Science, Scopus, and ProQuest were searched on July 24, 2019. Quality assessment was undertaken using ARRIVE, STROBE, and CARE (Animal Research: Reporting In Vivo Experiments, Strengthening the Reporting of Observational Studies in Epidemiology, and the Case Report Statement and Checklist, respectively). Results: Overall, 131 studies met the inclusion criteria, including 799 specimens and 2,823 patients who sustained 3,246 injuries. Laboratory studies showed a preponderance of failures at the MTJ, a viscoelastic behavior of muscle-tendon units, and damage accumulation at the MTJ with repetitive loading. Observational studies showed that 35% of injuries occurred in the tendon midsubstance; 28%, at the MTJ; 18%, at the tendon-bone junction; 13%, within the muscle belly and that 6% were tendon avulsions including a bone fragment. The biceps femoris was the most injured muscle (25%), followed by the supraspinatus (12%) and the Achilles tendon (9%). The most common symptoms were hematoma and/or swelling, tenderness, edema and muscle/tendon retraction. The onset of injury was consistent with tissue fatigue at all injury sites except for tendon avulsions, where 63% of the injuries were caused by an evident trauma. Conclusion: Excluding traumatic tendon avulsions, most injuries were consistent with the hypothesis that material fatigue damage accumulated during repetitive submaximal loading regimens. If supported by data from better imaging modalities, this has implications for improving injury detection, prevention, and training regimens.

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Ker, James. « The Violin Heart ». Clinical Medicine Insights : Cardiology 4 (janvier 2010) : 117954681000400. http://dx.doi.org/10.1177/117954681000400002.

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Left ventricular false tendons are thin, fibromuscular structures which traverse the left ventricular cavity. They are thought to be intracavitary radiations of the bundle of His. Usually these tendons span between the interventricular septum and the lateral wall or a papillary muscle. They have been known to be a source of innocent and musical murmurs. In this case report a peculiar left ventricular false tendon is shown—one extending between the two papillary muscles, giving the appearance of a musical note. During ventricular diastole the tendon is pulled taut between the two heads of the papillary muscles and during ventricular systole the tendon relaxes. The echocardiographic characteristics and possible long term implications are discussed.

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Roberts, Thomas J., et Emanuel Azizi. « The series-elastic shock absorber : tendons attenuate muscle power during eccentric actions ». Journal of Applied Physiology 109, n^o 2 (août 2010) : 396–404. http://dx.doi.org/10.1152/japplphysiol.01272.2009.

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Elastic tendons can act as muscle power amplifiers or energy-conserving springs during locomotion. We used an in situ muscle-tendon preparation to examine the mechanical function of tendons during lengthening contractions, when muscles absorb energy. Force, length, and power were measured in the lateral gastrocnemius muscle of wild turkeys. Sonomicrometry was used to measure muscle fascicle length independently from muscle-tendon unit (MTU) length, as measured by a muscle lever system (servomotor). A series of ramp stretches of varying velocities was applied to the MTU in fully activated muscles. Fascicle length changes were decoupled from length changes imposed on the MTU by the servomotor. Under most conditions, muscle fascicles shortened on average, while the MTU lengthened. Energy input to the MTU during the fastest lengthenings was −54.4 J/kg, while estimated work input to the muscle fascicles during this period was only −11.24 J/kg. This discrepancy indicates that energy was first absorbed by elastic elements, then released to do work on muscle fascicles after the lengthening phase of the contraction. The temporary storage of energy by elastic elements also resulted in a significant attenuation of power input to the muscle fascicles. At the fastest lengthening rates, peak instantaneous power input to the MTU reached −2,143.9 W/kg, while peak power input to the fascicles was only −557.6 W/kg. These results demonstrate that tendons may act as mechanical buffers by limiting peak muscle forces, lengthening rates, and power inputs during energy-absorbing contractions.

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Maas, Huub, Richard T. Jaspers, Guus C. Baan et Peter A. Huijing. « Myofascial force transmission between a single muscle head and adjacent tissues : length effects of head III of rat EDL ». Journal of Applied Physiology 95, n^o 5 (novembre 2003) : 2004–13. http://dx.doi.org/10.1152/japplphysiol.00220.2003.

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Force transmission from muscle fibers via the connective tissue network (i.e., myofascial force transmission) is an important determinant of muscle function. This study investigates the role of myofascial pathways for force transmission from multitendoned extensor digitorum longus (EDL) muscle within an intact anterior crural compartment. Effects of length changes exclusively of head III of rat EDL muscle (EDL III) on myofascial force transmission were assessed. EDL III was lengthened at the distal tendon. For different lengths of EDL III, isometric forces were measured at the distal tendon of EDL III, as well as at the proximal tendon of whole EDL and at the distal tendons of tibialis anterior and extensor hallucis longus (TA+EHL) muscles. Lengthening of EDL III caused high changes in force exerted at the distal tendon of EDL III (from 0 to 1.03 ± 0.07 N). In contrast, only minor changes were found in force exerted at the proximal EDL tendon (from 2.37 ± 0.09 to 2.53 ± 0.10 N). Increasing the length of EDL III decreased TA+EHL force significantly (by 7%, i.e., from 5.62 ± 0.27 to 5.22 ± 0.32 N). These results show that force is transmitted between EDL III and adjacent tissues via myofascial pathways. Optimal force exerted at the distal tendon of EDL III (1.03 ± 0.07 N) was more than twice the force expected on the basis of the physiological cross-sectional area of EDL III muscle fibers (0.42 N). Therefore, a substantial fraction of this force must originate from sources other than EDL III. It is concluded that myofascial pathways play an important role in force transmission from multitendoned muscles.

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Schneider, Lawrence H. « Tendon Transfers in Muscle and Tendon Loss ». Hand Clinics 4, n^o 2 (mai 1988) : 267–72. http://dx.doi.org/10.1016/s0749-0712(21)01141-0.

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Farcy, Stevy, Antoine Nordez, Sylvain Dorel, Hugo Hauraix, Pierre Portero et Giuseppe Rabita. « Interaction between gastrocnemius medialis fascicle and Achilles tendon compliance : a new insight on the quick-release method ». Journal of Applied Physiology 116, n^o 3 (1 février 2014) : 259–66. http://dx.doi.org/10.1152/japplphysiol.00309.2013.

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The insufficient temporal resolution of imaging devices has made the analysis of very fast movements, such as those required to measure active muscle-tendon unit stiffness, difficult. Thus the relative contributions of tendon, aponeurosis, and fascicle to muscle-tendon unit compliance remain to be determined. The present study analyzed the dynamic interactions of fascicle, tendon, and aponeurosis in human gastrocnemius medialis during the first milliseconds of an ankle quick-release movement, using high-frame-rate ultrasonography (2,000 frames/s). Nine subjects performed the tests in random order at six levels of maximal voluntary contraction (MVC) (30% to 80% of MVC). These tests were carried out with the ultrasound probe placed on the muscle belly and on the myotendinous junction. Tendon, muscle fascicle, and aponeurosis length changes were quantified in relation to shortening of the muscle-tendon unit during the first few milliseconds following the release. The tendon was the main contributor (around 72%) to the shortening of the muscle-tendon unit, whereas the muscle fascicle and aponeurosis contributions were 18% and 10%, respectively. Because these structures can be considered in series, the quantified contributions can be regarded as relative contributions to muscle-tendon compliance. These contributions were not modified with the level of MVC or the time range used for the analysis between 10 and 25 ms. The constant contribution of tendon, muscle fascicle, and aponeurosis to muscle-tendon unit compliance may help to simplify the mechanism of compliance regulation and to maintain the important role of tendons in enhancing work output and movement efficiency.

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Abe, Shinichi, et Masahito Yamamoto. « Factors Involved in Morphogenesis in the Muscle–Tendon–Bone Complex ». International Journal of Molecular Sciences 22, n^o 12 (14 juin 2021) : 6365. http://dx.doi.org/10.3390/ijms22126365.

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A decline in the body’s motor functions has been linked to decreased muscle mass and function in the oral cavity and throat; however, aging of the junctions of the muscles and bones has also been identified as an associated factor. Basic and clinical studies on the muscles, tendons and bones, each considered independently, have been published. In recent years, however, research has focused on muscle attachment as the muscle–tendon–bone complex from various perspectives, and there is a growing body of knowledge on SRY-box9 (Sox9) and Mohawk(Mkx), which has been identified as a common controlling factor and a key element. Myostatin, a factor that inhibits muscle growth, has been identified as a potential key element in the mechanisms of lifetime structural maintenance of the muscle–tendon–bone complex. Findings in recent studies have also uncovered aspects of the mechanisms of motor organ complex morphostasis in the superaged society of today and will lay the groundwork for treatments to prevent motor function decline in older adults.

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Lieber, R. L., G. J. Loren et J. Friden. « In vivo measurement of human wrist extensor muscle sarcomere length changes ». Journal of Neurophysiology 71, n^o 3 (1 mars 1994) : 874–81. http://dx.doi.org/10.1152/jn.1994.71.3.874.

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1. Human extensor carpi radialis brevis (ECRB) sarcomere length was measured intraoperatively in five subjects using laser diffraction. 2. In a separate cadaveric study, ECRB tendons were loaded to the muscle's predicted maximum tetanic tension, and tendon strain was measured to estimate active sarcomere shortening at the expense of tendon lengthening. 3. As the wrist joint was passively flexed from full extension to full flexion, ECRB sarcomere length increased from 2.6 to 3.4 microns at a rate of 7.6 nm/deg joint angle rotation. Correcting for tendon elongation during muscle activation yielded an active sarcomere length range of 2.44 to 3.33 microns. Maximal predicted sarcomere shortening accompanying muscle activation was dependent on initial sarcomere length and was always < 0.15 microns, suggesting a minimal effect of tendon compliance. 4. Thin filament lengths measured from electron micrographs of muscle biopsies obtained from the same region of the ECRB muscles were 1.30 +/- .027 (SE) microns whereas thick filaments were 1.66 +/- .027 microns long, suggesting an optimal sarcomere length of 2.80 microns and a maximum sarcomere length for active force generation of 4.26 microns. 5. These experiments demonstrate that human skeletal muscles can function on the descending limb of their sarcomere length-tension relationship under physiological conditions. Thus, muscle force changes during joint rotation are an important component of the motor control system.

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Luo, Xi, Guofeng Cai, Kun Ma et Aiqi Cai. « Construction and Simulation of Biomechanical Model of Human Hip Joint Muscle-Tendon Assisted by Elastic External Tendon by Hill Muscle Model ». Computational Intelligence and Neuroscience 2022 (2 août 2022) : 1–14. http://dx.doi.org/10.1155/2022/1987345.

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Based on the Hill muscle model (HMM), a biomechanical model of human hip muscle tendon assisted by elastic external tendon (EET) was preliminarily established to investigate and analyze the biomechanical transition between the hip joint (HJ) and related muscle tendons. Using the HMM, the optimal muscle fiber length and muscle force scaling variables were introduced by means of constrained optimization problems and were optimized. The optimized HMM was constructed with human parameters of 170 cm and 70 kg. The biomechanical model simulation test of the hip muscle tendon was performed in the automatic dynamic analysis of mechanical systems (ADAMS) software to analyze and optimize the changes in the root mean square error (RMSE), biological moment, muscle moment distribution coefficient (MDC), muscle moment, muscle force, muscle power, and mechanical work of the activation curves of the hip major muscle, iliopsoas muscle, rectus femoris muscle, and hamstring muscle under analyzing the optimized HMM and under different EET auxiliary stiffnesses from the joint moment level, joint level, and muscle level, respectively. It was found that the trends of the output joint moment of the optimized HMM and the biological moment of the human HJ were basically the same, r2 = 0.883 and RMSE = 0.18 Nm/kg, and the average metabolizable energy consumption of the HJ was (243.77 ± 1.59) J. In the range of 35%∼65% of gait cycle (GC), the auxiliary moment showed a significant downward trend with the increase of EET stiffness, when the EET stiffness of the human body was less than 200 Nm/rad, the biological moment of the human HJ gradually decreased with the increase of EET stiffness, and the MDC of the iliopsoas and hamstring muscles gradually decreased; when the EET stiffness was greater than 200 Nm/rad, the increase of the total moment of the extensor muscles significantly increased, the MDC of the gluteus maximus and rectus muscles gradually increased, and the gluteus maximus and hamstring muscle moments and muscle forces gradually increased; the results show that the optimized muscle model based on Hill can reflect the law of human movement and complete the simulation test of HJ movements, which provides a new idea for the analysis of energy migration in the musculoskeletal system of the lower limb.

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Kalliokoski, Kari K., Henning Langberg, Ann Kathrine Ryberg, Celena Scheede-Bergdahl, Simon Doessing, Andreas Kjaer, Robert Boushel et Michael Kjaer. « The effect of dynamic knee-extension exercise on patellar tendon and quadriceps femoris muscle glucose uptake in humans studied by positron emission tomography ». Journal of Applied Physiology 99, n^o 3 (septembre 2005) : 1189–92. http://dx.doi.org/10.1152/japplphysiol.00283.2005.

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Both tendon and peritendinous tissue show evidence of metabolic activity, but the effect of acute exercise on substrate turnover is unknown. We therefore examined the influence of acute exercise on glucose uptake in the patellar and quadriceps tendons during dynamic exercise in humans. Glucose uptake was measured in five healthy men in the patellar and quadriceps tendons and the quadriceps femoris muscle at rest and during dynamic knee-extension exercise (25 W) using positron emission tomography and [18F]-2-fluoro-2-deoxy-d-glucose ([18F]FDG). Glucose uptake index was calculated by dividing the tissue activity with blood activity of [18F]FDG. Exercise increased glucose uptake index by 77% in the patellar tendon (from 0.30 ± 0.09 to 0.51 ± 0.16, P = 0.03), by 106% in the quadriceps tendon (from 0.37 ± 0.15 to 0.75 ± 0.36, P = 0.02), and by 15-fold in the quadriceps femoris muscle (from 0.31 ± 0.11 to 4.5 ± 1.7, P = 0.005). The exercise-induced increase in the glucose uptake in neither tendon correlated with the increase in glucose uptake in the quadriceps muscle ( r = −0.10, P = 0.87 for the patellar tendon and r = −0.30, P = 0.62 for the quadriceps tendon). These results show that tendon glucose uptake is increased during exercise. However, the increase in tendon glucose uptake is less pronounced than in muscle and the increases are uncorrelated. Thus tendon glucose uptake is likely to be regulated by mechanisms independently of those regulating skeletal muscle glucose uptake.

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Fouré, Alexandre, Antoine Nordez et Christophe Cornu. « Effects of eccentric training on mechanical properties of the plantar flexor muscle-tendon complex ». Journal of Applied Physiology 114, n^o 5 (1 mars 2013) : 523–37. http://dx.doi.org/10.1152/japplphysiol.01313.2011.

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Eccentric training is a mechanical loading classically used in clinical environment to rehabilitate patients with tendinopathies. In this context, eccentric training is supposed to alter tendon mechanical properties but interaction with the other components of the muscle-tendon complex remains unclear. The aim of this study was to determine the specific effects of 14 wk of eccentric training on muscle and tendon mechanical properties assessed in active and passive conditions in vivo. Twenty-four subjects were randomly divided into a trained group ( n = 11) and a control group ( n = 13). Stiffness of the active and passive parts of the series elastic component of plantar flexors were determined using a fast stretch during submaximal isometric contraction, Achilles tendon stiffness and dissipative properties were assessed during isometric plantar flexion, and passive stiffness of gastrocnemii muscles and Achilles tendon were determined using ultrasonography while ankle joint was passively moved. A significant decrease in the active part of the series elastic component stiffness was found ( P < 0.05). In contrast, a significant increase in Achilles tendon stiffness determined under passive conditions was observed ( P < 0.05). No significant change in triceps surae muscles and Achilles tendon geometrical parameters was shown ( P > 0.05). Specific changes in muscle and tendon involved in plantar flexion are mainly due to changes in intrinsic mechanical properties of muscle and tendon tissues. Specific assessment of both Achilles tendon and plantar flexor muscles allowed a better understanding of the functional behavior of the muscle-tendon complex and its adaptation to eccentric training.

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Venkatapathy, Santhi, et Rajesh Bhargavan. « Clinical Assessment of Existence of Palmaris Longus Muscle among South Indian Population ». Journal of Hand Surgery (Asian-Pacific Volume) 25, n^o 02 (20 avril 2020) : 137–42. http://dx.doi.org/10.1142/s2424835520500149.

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Background: Palmaris longus tendon is often used as a donor tendon by surgeons in tendon grafts. It is one of the flexor muscles of the forearm and documented well for its variations in both morphology and number of tendons. Prevalence of absence of this muscle varies among the individuals of same population and individuals of various ethnic groups. The aim of this study was to assess the existence of Palmaris longus muscle within a group of students and its association with side of the limb and gender of the individual. Methods: Three hundred medical students of 150 males and 150 females with age group of 18–21 years were clinically assessed. The standard Schaffer’s test was used for the assessment of PL tendon. If the tendon was not found in this test, the confirmation was done by other four tests. Results: Results of this study shows that an overall absence of palmaris longus muscle in both sexes was found to be 32%, out of which 21% absence was found in males and 43% absence found in females. Among the males, the unilateral agenesis was seen in 16% and bilateral agenesis in 4% and in females the unilateral agenesis was seen in 29% and bilateral agenesis seen in 14%. Conclusions: To conclude; in the present study, prevalence of Palmaris longus muscle agenesis was found to be more in female subjects on their left side. Surgeons who plan for tendon reconstructive procedures should know variations of Palmaris longus muscle and its clinical assessment.

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Rosenfeld, Peter F., Jonathan Dick et Terence S. Saxby. « The Response of the Flexor Digitorum Longus and Posterior Tibial Muscles to Tendon Transfer and Calcaneal Osteotomy for Stage II Posterior Tibial Tendon Dysfunction ». Foot & ; Ankle International 26, n^o 9 (septembre 2005) : 671–74. http://dx.doi.org/10.1177/107110070502600902.

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Background: The purpose of this prospective study was to evaluate the response of the flexor digitorum longus (FDL) and posterior tibial (PT) muscles to FDL tendon transfer and medial displacement calcaneal osteotomy for stage II posterior tibial tendon dysfunction (PTTD). Methods: Twelve patients were divided into two groups, depending on whether the PTtendon was excised(Excised Tendon Group) or left intact (Intact Tendon Group). The muscle volumes of the FDL and PT muscles in both legs were measured and compared, using cross-sectional area (CSA) analysis of preoperative and postoperative MRI. Results: Preoperatively, there was an average 11% reduction in the PT muscle volume and a 17% increase in the FDL muscle volume from the normal contralateral side in both groups. One year after surgery (average 13.4 months) in both groups, the FDL muscle volume had increased by an average of 27% and the PT muscle volume had decreased by 23% compared to the contralateral normal side. The FDL volume increased by 44% in the Excised Tendon Group compared to 11% in the Intact Tendon Group. The PT muscle volumes were not assessed in the Excised Tendon Group because all PT muscle had been replaced by fatty infiltration. The PT volumes in the Intact Tendon Group decreased further from a 6% reduction preoperatively to a 23% reduction postoperatively compared to the normal contralateral side. The American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot scores increased from 50 preoperatively to 88 at 1 year after surgery. There was no difference in the scores between the Excised Tendon (47 to 87) and Intact Tendon (53 to 89) groups. Conclusion: We concluded that the FDL muscle hypertrophies in response to a failing PT muscle. This hypertrophy continues after FDL transfer and medial displacement calcaneal osteotomy. With excision of the PT tendon, the FDL undergoes greater hypertrophy than if the tendon is left attached. The PT muscle continues to atrophy and undergoes complete fatty replacement if the tendon is excised. Transfer of the FDL and medial displacement calcaneal osteotomy produce a satisfactory improvement in hindfoot function; the outcome was the same whether the PT tendon was sacrificed or left intact.

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Verschueren, Sabine M. P., Paul J. Cordo et Stephan P. Swinnen. « Representation of Wrist Joint Kinematics by the Ensemble of Muscle Spindles From Synergistic Muscles ». Journal of Neurophysiology 79, n^o 5 (1 mai 1998) : 2265–76. http://dx.doi.org/10.1152/jn.1998.79.5.2265.

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Verschueren, Sabine M. P., Paul J. Cordo, and Stephan P. Swinnen. Representation of wrist joint kinematics by the ensemble of muscle spindles from synergistic muscles. J. Neurophysiol. 79: 2265–2276, 1998. Proprioceptive information about movement is transmitted to the central nervous system by a variety of receptor types, which are widely distributed among the muscles, joints, and skin. Muscle spindles are known to be an important and reliable source of information for the perception of movement kinematics. Previous studies that focused on the characteristics of single muscle spindle firing patterns have left the impression that each receptor fires in relation to a number of kinematic variables, leaving the following question unanswered: what role is played by the ensemble of muscle spindles within the same muscle or within synergistic muscles? The study described in this paper addressed whether the perception of joint position and velocity is based on the net input of muscle spindles residing in all synergistic muscles crossing a joint. Normal human adults performed a motor coordination task that required perception of joint velocity and dynamic position at the wrist. The task was to open the left hand briskly as the right wrist was passively rotated in the flexion direction through a prescribed target angle. In randomly occurring trials, the tendons to three muscles [extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), and extensor digitorum (ED)] were vibrated either individually or in different combinations during the performance of the motor task. Tendon vibration is known to distort muscle spindle firing patterns, and consequently, kinesthesia. By comparing performance errors with and without tendon vibration, the relative influences of muscle spindles residing in ECR, ECU, and ED were quantified. Vibration of the individual ECR, ECU, or ED tendons produced systematic undershoot errors in performance, consistent with the misperception of wrist velocity and dynamic position. Performance errors were larger when combinations of, rather than individual, muscle tendons were vibrated. The error resulting from simultaneous vibration of ECR and ECU was roughly equal to the sum of the errors produced by vibration of the individual tendons. These effects of vibrating synergistic tendons at the wrist suggest that kinesthesia is derived from the integrated input of muscle spindles from all synergistic muscles.

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Muthukrishnan, Subbaratnam, Seulgi Mun, Mi Y. Noh, Erika R. Geisbrecht et Yasuyuki Arakane. « Insect Cuticular Chitin Contributes to Form and Function ». Current Pharmaceutical Design 26, n^o 29 (4 septembre 2020) : 3530–45. http://dx.doi.org/10.2174/1381612826666200523175409.

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: Chitin contributes to the rigidity of the insect cuticle and serves as an attachment matrix for other cuticular proteins. Deficiency of chitin results in abnormal embryos, cuticular structural defects and growth arrest. When chitin is not turned over during molting, the developing insect is trapped inside the old cuticle. Partial deacetylation of cuticular chitin is also required for proper laminar organization of the cuticle and vertical pore canals, molting, and locomotion. Thus, chitin and its modifications strongly influence the structure of the exoskeleton as well as the physiological functions of the insect. : Internal tendons and specialized epithelial cells called “tendon cells” that arise from the outer layer of epidermal cells provide attachment sites at both ends of adult limb muscles. Membrane processes emanating from both tendon and muscle cells interdigitate extensively to strengthen the attachment of muscles to the extracellular matrix (ECM). Protein ligands that bind to membrane-bound integrin complexes further enhance the adhesion between muscles and tendons. Tendon cells contain F-actin fiber arrays that contribute to their rigidity. In the cytoplasm of muscle cells, proteins such as talin and other proteins provide attachment sites for cytoskeletal actin, thereby increasing integrin binding and activation to mechanically couple the ECM with actin in muscle cells. Mutations in integrins and their ligands, as well as depletion of chitin deacetylases, result in defective locomotion and muscle detachment from the ECM. Thus, chitin in the cuticle and chitin deacetylases strongly influence the shape and functions of the exoskeleton as well as locomotion of insects.

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Davis, Max E., Jonathan P. Gumucio, Kristoffer B. Sugg, Asheesh Bedi et Christopher L. Mendias. « MMP inhibition as a potential method to augment the healing of skeletal muscle and tendon extracellular matrix ». Journal of Applied Physiology 115, n^o 6 (15 septembre 2013) : 884–91. http://dx.doi.org/10.1152/japplphysiol.00137.2013.

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The extracellular matrix (ECM) of skeletal muscle and tendon is composed of different types of collagen molecules that play important roles in the transmission of forces throughout the body, and in the repair and regeneration of injured tissues. Fibroblasts are the primary cells in muscle and tendon that maintain, repair, and modify the ECM in response to mechanical loading, injury, and inactivity. Matrix metalloproteinases (MMPs) are enzymes that digest collagen and other structural molecules, which are synthesized and excreted by fibroblasts. MMPs are required for baseline ECM homeostasis, but disruption of MMP regulation due to injury or disease can alter the normal ECM architecture and prevent proper force transmission. Chronic injuries and diseases of muscles and tendons can be severely debilitating, and current therapeutic modalities to enhance healing are quite limited. This review will discuss the mechanobiology of MMPs, and the potential use of MMP inhibitors to improve the treatment of injured and diseased skeletal muscle and tendon tissue.

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Herbert, R. D., B. Bolsterlee et S. C. Gandevia. « Passive changes in muscle length ». Journal of Applied Physiology 126, n^o 5 (1 mai 2019) : 1445–53. http://dx.doi.org/10.1152/japplphysiol.00673.2018.

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This review, the first in a series of minireviews on the passive mechanical properties of skeletal muscles, seeks to summarize what is known about the muscle deformations that allow relaxed muscles to lengthen and shorten. Most obviously, when a muscle lengthens, muscle fascicles elongate, but this is not the only mechanism by which muscles change their length. In pennate muscles, elongation of muscle fascicles is accompanied by changes in pennation and changes in fascicle curvature, both of which may contribute to changes in muscle length. The contributions of these mechanisms to change in muscle length are usually small under passive conditions. In very pennate muscles with long aponeuroses, fascicle shear could contribute substantially to changes in muscle length. Tendons experience moderate axial strains even under passive loads, and, because tendons are often much longer than muscle fibers, even moderate tendon strains may contribute substantially to changes in muscle length. Data obtained with new imaging techniques suggest that muscle fascicle and aponeurosis strains are highly nonuniform, but this is yet to be confirmed. The development, validation, and interpretation of continuum muscle models informed by rigorous measurements of muscle architecture and material properties should provide further insights into the mechanisms that allow relaxed muscles to lengthen and shorten.

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Seyfarth, A., R. Blickhan et J. L. Van Leeuwen. « Optimum take-off techniques and muscle design for long jump ». Journal of Experimental Biology 203, n^o 4 (15 février 2000) : 741–50. http://dx.doi.org/10.1242/jeb.203.4.741.

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A two-segment model based on Alexander (1990; Phil. Trans. R. Soc. Lond. B 329, 3–10) was used to investigate the action of knee extensor muscles during long jumps. A more realistic representation of the muscle and tendon properties than implemented previously was necessary to demonstrate the advantages of eccentric force enhancement and non-linear tendon properties. During the take-off phase of the long jump, highly stretched leg extensor muscles are able to generate the required vertical momentum. Thereby, serially arranged elastic structures may increase the duration of muscle lengthening and dissipative operation, resulting in an enhanced force generation of the muscle-tendon complex. To obtain maximum performance, athletes run at maximum speed and have a net loss in mechanical energy during the take-off phase. The positive work done by the concentrically operating muscle is clearly less than the work done by the surrounding system on the muscle during the eccentric phase. Jumping performance was insensitive to changes in tendon compliance and muscle speed, but was greatly influenced by muscle strength and eccentric force enhancement. In agreement with a variety of experimental jumping performances, the optimal jumping technique (angle of attack) was insensitive to the approach speed and to muscle properties (muscle mass, the ratio of muscle fibre to tendon cross-sectional area, relative length of fibres and tendon). The muscle properties also restrict the predicted range of the angle of the velocity vector at take-off.

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Clark, William H., et Jason R. Franz. « Do triceps surae muscle dynamics govern non-uniform Achilles tendon deformations ? » PeerJ 6 (12 juillet 2018) : e5182. http://dx.doi.org/10.7717/peerj.5182.

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The human Achilles tendon (AT) consists of sub-tendons arising from the gastrocnemius and soleus muscles that exhibit non-uniform tissue displacements thought to facilitate some independent actuation. However, the mechanisms governing non-uniform displacement patterns within the AT, and their relevance to triceps surae muscle contractile dynamics, have remained elusive. We used a dual-probe ultrasound imaging approach to investigate triceps surae muscle dynamics (i.e., medial gastrocnemius-GAS, soleus-SOL) as a determinant of non-uniform tendon tissue displacements in the human AT. We hypothesized that superficial versus deep differences in AT tissue displacements would be accompanied by and correlate with anatomically consistent differences in GAS versus SOL muscle shortening. Nine subjects performed ramped maximum voluntary isometric contractions at each of five ankle joint angles spanning 10° dorsiflexion to 30° plantarflexion. For all conditions, SOL shortened by an average of 78% more than GAS during moment generation. This was accompanied by, on average, 51% more displacement in the deep versus superficial region of the AT. The magnitude of GAS and SOL muscle shortening positively correlated with displacement in their associated sub-tendons within the AT. Moreover, and as hypothesized, superficial versus deep differences in sub-tendon tissue displacements positively correlated with anatomically consistent differences in GAS versus SOL muscle shortening. We present the first in vivo evidence that triceps surae muscle dynamics may precipitate non-uniform displacement patterns in the architecturally complex AT.

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Biewener, A. A., D. D. Konieczynski et R. V. Baudinette. « In vivo muscle force-length behavior during steady-speed hopping in tammar wallabies. » Journal of Experimental Biology 201, n^o 11 (1 juin 1998) : 1681–94. http://dx.doi.org/10.1242/jeb.201.11.1681.

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Moderate to large macropodids can increase their speed while hopping with little or no increase in energy expenditure. This has been interpreted by some workers as resulting from elastic energy savings in their hindlimb tendons. For this to occur, the muscle fibers must transmit force to their tendons with little or no length change. To test whether this is the case, we made in vivo measurements of muscle fiber length change and tendon force in the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies Macropus eugenii as they hopped at different speeds on a treadmill. Muscle fiber length changes were less than +/-0.5 mm in the plantaris and +/-2.2 mm in the lateral gastrocnemius, representing less than 2 % of total fiber length in the plantaris and less than 6 % in the lateral gastrocnemius, with respect to resting length. The length changes of the plantaris fibers suggest that this occurred by means of elastic extension of attached cross-bridges. Much of the length change in the lateral gastrocnemius fibers occurred at low force early in the stance phase, with generally isometric behavior at higher forces. Fiber length changes did not vary significantly with increased hopping speed in either muscle (P>0.05), despite a 1. 6-fold increase in muscle-tendon force between speeds of 2.5 and 6.0 m s-1. Length changes of the PL fibers were only 7+/-4 % and of the LG fibers 34+/-12 % (mean +/- S.D., N=170) of the stretch calculated for their tendons, resulting in little net work by either muscle (plantaris 0.01+/-0.03 J; gastrocnemius -0.04+/-0.30 J; mean +/- s.d. ). In contrast, elastic strain energy stored in the tendons increased with increasing speed and averaged 20-fold greater than the shortening work performed by the two muscles. These results show that an increasing amount of strain energy stored within the hindlimb tendons is usefully recovered at faster steady hopping speeds, without being dissipated by increased stretch of the muscles' fibers. This finding supports the view that tendon elastic saving of energy is an important mechanism by which this species is able to hop at faster speeds with little or no increase in metabolic energy expenditure.

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Rubenson, Jonas. « More than Meat and a Motor : The Diverse Biomechanical Roles of Skeletal Muscle and Their Place in ‘Semi-Living’ Machines ». Leonardo 48, n^o 2 (avril 2015) : 176–77. http://dx.doi.org/10.1162/leon_a_00977.

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The biomechanical roles of skeletal muscle and their tendons are diverse. Perhaps most intuitively, muscle is regarded as a biological ‘motor’ that provides the work required for accelerating the body and overcoming aero- and hydrodynamic forces. With detailed biomechanical analyses, more intricate roles of the muscle-tendon unit have been uncovered, ranging from energy recyclers, to shock absorbers and capacitors. The functional scope of muscle-tendon tissue makes it an attractive choice for exploring bio-machine integration. Research and cross-disciplinary collaboration at SymbioticA offers a testbed for scientific and artistic exploration into engineered muscle-tendon constructs and the broader philosophical debate surrounding their place in ‘semi-living’ machine systems.

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Huang, Brady, Mini Pathria et Anthony Tadros. « Muscle-Tendon-Enthesis Unit ». Seminars in Musculoskeletal Radiology 22, n^o 03 (23 mai 2018) : 263–74. http://dx.doi.org/10.1055/s-0038-1641570.

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AbstractInjuries to the muscle-tendon-enthesis unit are common and a significant source of pain and loss of function. This article focuses on the important anatomical and biomechanical considerations for each component of the muscle-tendon-enthesis unit. We review normal and pathologic conditions affecting this unit, illustrating the imaging appearance of common disorders on magnetic resonance imaging and ultrasound. Knowledge of the anatomy and biomechanics of these structures is crucial for the radiologist to make accurate diagnoses and provide clinically relevant assessments.

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Bernabei, Michel, Jaap H. van Dieën, Guus C. Baan et Huub Maas. « Significant mechanical interactions at physiological lengths and relative positions of rat plantar flexors ». Journal of Applied Physiology 118, n^o 4 (15 février 2015) : 427–36. http://dx.doi.org/10.1152/japplphysiol.00703.2014.

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In situ studies involving supraphysiological muscle lengths and relative positions have shown that connective tissue linkages connecting adjacent muscles can transmit substantial forces, but the physiological significance is still subject to debate. The present study investigates effects of such epimuscular myofascial force transmission in the rat calf muscles. Unlike previous approaches, we quantified the mechanical interaction between the soleus (SO) and the lateral gastrocnemius and plantaris complex (LG+PL) applying a set of muscle lengths and relative positions corresponding to the range of knee and ankle angles occurring during normal movements. In nine deeply anesthetized Wistar rats, the superficial posterior crural compartment was exposed, and distal and proximal tendons of LG+PL and the distal SO tendon were severed and connected to force transducers. The target muscles were excited simultaneously. We found that SO active and passive tendon force was substantially affected by proximally lengthening of LG+PL mimicking knee extension (10% and 0.8% of maximal active SO force, respectively; P < 0.05). Moreover, SO relative position significantly changed the LG+PL length-force relationship, resulting in nonunique values for passive slack-length and optimum-length estimates. We conclude that also, for physiological muscle conditions, isometric force of rat triceps surae muscles is determined by its muscle-tendon unit length as well as by the length and relative position of its synergists. This has implications for understanding the neuromechanics of skeletal muscle in normal and pathological conditions, as well as for studies relying on the assumption that muscles act as independent force actuators.

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Trestik, C. L., et R. L. Lieber. « Relationship Between Achilles Tendon Mechanical Properties and Gastrocnemius Muscle Function ». Journal of Biomechanical Engineering 115, n^o 3 (1 août 1993) : 225–30. http://dx.doi.org/10.1115/1.2895479.

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Strain was measured along the length of frog (Rana pipiens) gastrocnemius muscle-tendon units (MTU). Maximum muscle tension (P0) was measured, and the MTU was passively loaded to P0. Strain at P0 was measured at eight intervals along the tendon and aponeurosis and was approximately two percent for all regions except the aponeurosis region closest to the muscle fibers where it was about six percent. A computer model predicted sarcomere shortening of up to 0.5 μm due to tendon lengthening which demonstrates that tendons provide a more complex physiological function than simply transmitting muscle force to bones.

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Mohammadnezhad, Ghasem, Hasan Matin Homaee et Farshad Ghazalian. « Effect of 6 Weeks of Aerobic Training on TGF-Β1, Myostatin and Matrix Metalloproteinase 9 Genes Expression in the Tendon of Fast- and Slow-Twitch Muscles of Male Wistar Rats ». Journal of Arak University of Medical Sciences 23, n^o 3 (1 août 2020) : 278–91. http://dx.doi.org/10.32598/jams.23.3.5849.2.

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Background and Aim: Tendon, like the skeletal muscle, exhibits mechanical and morphological adaptations resulted from exercise training; however, little is known about the basic cellular and molecular mechanisms that regulate these responses. The aim of the present study was therefore to investigate the effect of 6 weeks of aerobic training on the TGF-β1, myostatin and MMP9 mRNAs expression in the tendon of fast- and slow-twitch muscles. Methods & Materials For this purpose, 12 male Wistar rats at 8 weeks of age were randomly divided into two groups: experimental (n=6) and control (n=6). The exercise group performed aerobic training for 6 weeks, 5 sessions per week. Forty-eight hours after the last training session, all rats were sacrificed and the tendons of soleus and Extensor Digitorum Longus (EDL) muscles were extracted. Expression of TGF-β1, myostatin and MMP9 mRNAs were assayed using RealTime-PCR. Independent t-test was also used for statistical analysis. Ethical Considerations: All stages of the study were conducted according to the ethical guidelines and authorization of Research Deputy of Islamic Azad University, Central Tehran Branch No. IR.IAU.PS.REC.1398.296. Results: The results showed that the expression of TGF-β1 mRNA in EDL and soleus tendons significantly increased (P≤0.001), whereas the expression of myostatin in EDL tendon was significantly reduced (P≤ 0.001). Increased mRNA expression of MMP9 in the tendon of EDL and soleus muscles was not statistically significant (P>0.05). Conclusion: It seems that aerobic exercise can modulate the expression of genes involved in the regulation of tendon collagen in a muscle type-dependent manner.

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Hullfish, Todd J., Kathryn M. O’Connor et Josh R. Baxter. « Medial gastrocnemius muscle remodeling correlates with reduced plantarflexor kinetics 14 weeks following Achilles tendon rupture ». Journal of Applied Physiology 127, n^o 4 (1 octobre 2019) : 1005–11. http://dx.doi.org/10.1152/japplphysiol.00255.2019.

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Deficits in plantarflexor kinetics are associated with poor outcomes in patients following Achilles tendon rupture. In this longitudinal study, we analyzed the fascicle length and pennation angle of the medial gastrocnemius muscle and the length of the Achilles tendon using ultrasound imaging. To determine the relationship between muscle remodeling and deficits in plantarflexor kinetics measured at 14 wk after injury, we correlated the reduction in fascicle length and increase in pennation angle with peak torque measured during isometric and isokinetic plantarflexor contractions. We found that the medial gastrocnemius underwent an immediate change in structure, characterized by decreased length and increased pennation of the muscle fascicles. This decrease in fascicle length was coupled with an increase in tendon length. These changes in muscle-tendon structure persisted throughout the first 14 wk following rupture. Deficits in peak plantarflexor torque were moderately correlated with decreased fascicle length at 120 degrees per second ( R2 = 0.424, P = 0.057) and strongly correlated with decreased fascicle length at 210 degrees per second ( R2 = 0.737, P = 0.003). However, increases in pennation angle did not explain functional deficits. These findings suggest that muscle-tendon structure is detrimentally affected following Achilles tendon rupture. Plantarflexor power deficits are positively correlated with the magnitude of reductions in fascicle length. Preserving muscle structure following Achilles tendon rupture should be a clinical priority to maintain plantarflexor kinetics. NEW & NOTEWORTHY In our study, we found that when the Achilles tendon ruptures due to excessive biomechanical loading, the neighboring skeletal muscle undergoes rapid changes in its configuration. The magnitude of this muscle remodeling explains the amount of ankle power loss demonstrated by these patients once their Achilles tendons are fully healed. These findings highlight the interconnected relationship between muscle and tendon. Isolated injuries to the tendon stimulate detrimental changes to the muscle, thereby limiting joint-level function.

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ARSLAN, YUNUS ZIYA, et DERYA KARABULUT. « SENSITIVITY OF MODEL-PREDICTED MUSCLE FORCES OF PATIENTS WITH CEREBRAL PALSY TO VARIATIONS IN MUSCLE-TENDON PARAMETERS ». Journal of Mechanics in Medicine and Biology 21, n^o 01 (février 2021) : 2150008. http://dx.doi.org/10.1142/s0219519421500081.

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Computational musculoskeletal modeling and simulation platforms are efficient tools to gain insight into the muscular coordination of patients with motor disabilities such as cerebral palsy (CP). Muscle force predictions from simulation programs are influenced by the architectural and contractile properties of muscle-tendon units. In this study, we aimed to evaluate the sensitivity of major lower limb muscle forces in patients with CP to changes in muscle-tendon parameters. Open-access datasets of children with CP ([Formula: see text]) and healthy children ([Formula: see text]) were considered. Monte Carlo analysis was executed to specify how sensitive the muscle forces to perturbations between [Formula: see text]% and [Formula: see text]% of the nominal value of the maximum isometric muscle force, optimal muscle fiber length, muscle pennation angle, tendon slack length, and maximum contraction velocity of muscle. The sensitivity analysis revealed that muscle forces of CP patients and healthy individuals were most sensitive to perturbations in the tendon slack length ([Formula: see text]), while forces of CP patients were more sensitive to tendon slack length when compared to the healthy group ([Formula: see text]). Muscle forces of patients and healthy individuals were insensitive to the other four parameters ([Formula: see text]), except for the gracilis and sartorius muscles in which the proportion of optimal muscle fiber length to tendon slack length is higher than 1; forces of these two muscles were also sensitive to the optimal muscle fiber length. The results of this study are expected to contribute to our understanding of which parameters should be personalized when conducting musculoskeletal modeling and simulation of patients with CP.

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Wade, Logan, Glen A. Lichtwark et Dominic J. Farris. « Joint and muscle-tendon coordination strategies during submaximal jumping ». Journal of Applied Physiology 128, n^o 3 (1 mars 2020) : 596–603. http://dx.doi.org/10.1152/japplphysiol.00293.2019.

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Previous research has demonstrated that during submaximal jumping humans prioritize reducing energy consumption by minimizing countermovement depth. However, sometimes movement is constrained to a nonpreferred pattern, and this requires adaptation of neural control that accounts for complex interactions between muscle architecture, muscle properties, and task demands. This study compared submaximal jumping with either a preferred or a deep countermovement depth to examine how joint and muscle mechanics are integrated into the adaptation of coordination strategies in the deep condition. Three-dimensional motion capture, two force plates, electromyography, and ultrasonography were used to examine changes in joint kinetics and kinematics, muscle activation, and muscle kinematics for the lateral gastrocnemius and soleus. Results demonstrated that a decrease in ankle joint work during the deep countermovement depth was due to increased knee flexion, leading to unfavorably short biarticular muscle lengths and reduced active fascicle length change during ankle plantar flexion. Therefore, ankle joint work was likely decreased because of reduced active fascicle length change and operating position on the force-length relationship. Hip joint work was significantly increased as a result of altered muscle activation strategies, likely due to a substantially greater hip extensor muscle activation period compared with plantar flexor muscles during jumping. Therefore, coordination strategies at individual joints are likely influenced by time availability, where a short plantar flexor activation time results in dependence on muscle properties, instead of simply altering muscle activation, while the longer time for contraction of muscles at the hip allows for adjustments to voluntary neural control. NEW & NOTEWORTHY Using human jumping as a model, we show that adapting movement patterns to altered task demands is achieved differently by muscles across the leg. Because of proximal-to-distal sequencing, distal muscles (i.e., plantar flexors) have reduced activation periods and, as a result, rely on muscle contractile properties (force-length relationship) for adjusting joint kinetics. For proximal muscles that have greater time availability, voluntary activation is modulated to adjust muscle outputs.

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Józsa, László G. « ADVANCED HISTOPATHOLOGICAL TECHNIQUES IN DIAGNOSIS OF THE MUSCLE AND TENDON ALTERATIONS ». Journal of Musculoskeletal Research 04, n^o 04 (décembre 2000) : 303–9. http://dx.doi.org/10.1142/s0218957700000288.

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In this mini review, I will attempt to briefly provide the microscopic possibilities in the diagnosis of muscle and tendon disorders based on more than 1000 muscle and 2000 tendon biopsies. The routine histological sections and light microscopy are still of value in the diagnosis of tendon and muscle pathology. The morphologic methods are time-consuming, and consequently should be done step by step. In diagnostic muscle pathology, enzyme histochemistry, histomorphometry, transmission and scanning electron microscopy, and immunohistochemistry are the most reliable methods, while in tendon pathology, they are polarized light microscopy, electron microscopy and immunohistochemistry. However, the histopathological methods can be used not only in the diagnosis of muscle and tendon disorders, but can also predict the physical condition of muscles, detect the healing and regenerating processes and the effectivity of drug administration.

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Zhao, Heng, Yupeng Ren, Elliot J. Roth, Richard L. Harvey et Li-Qun Zhang. « Concurrent deficits of soleus and gastrocnemius muscle fascicles and Achilles tendon post stroke ». Journal of Applied Physiology 118, n^o 7 (1 avril 2015) : 863–71. http://dx.doi.org/10.1152/japplphysiol.00226.2014.

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Calf muscles and Achilles tendon play important roles in functional activities. However, it is not clear how biomechanical properties of the uniarticular soleus (SOL) and biarticular gastrocnemius muscle and Achilles tendon, including the fascicle length, pennation angle, and stiffness, change concurrently post stroke. Biomechanical properties of the medial gastrocnemius (GM) and soleus muscles were evaluated bilaterally in 10 hemiparetic stroke survivors using combined ultrasonography-biomechanical measurements. Biomechanical properties of the Achilles tendon including the length, cross-sectional area (CSA), stiffness, and Young's modulus were evaluated, together with calf muscle biomechanical properties. Gastrocnemius and SOL contributions were separated using flexed and extended knee positions. The impaired side showed decreased fascicle length (GM: 6%, P = 0.002 and SOL: 9%, P = 0.03, at full knee extension and 0° ankle dorsiflexion) and increased fascicular stiffness (GM: 64%, P = 0.005 and SOL: 19%, P = 0.012, at a common 50 N force level). In contrast, Achilles tendon on the impaired side showed changes in the opposite direction as the muscle fascicles with increased tendon length (5%, P < 0.001), decreased tendon CSA (5%, P = 0.04), decreased tendon stiffness (42%, P < 0.001) and Young's modulus (30%, P < 0.001) compared with the unimpaired side. The fascicle and tendon stiffness changes were correlated negatively to the corresponding fascicle and tendon length changes, and decrease in Achilles tendon stiffness was correlated to the increases of SOL and GM fascicular stiffness ( P < 0.05). Characterizations of calf muscle fascicles and Achilles tendon biomechanical properties help us better understand concurrent changes of fascicles and tendon as part of the calf muscle-tendon unit and facilitate development of more effective treatments.

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Hauraix, Hugo, Antoine Nordez et Sylvain Dorel. « Shortening behavior of the different components of muscle-tendon unit during isokinetic plantar flexions ». Journal of Applied Physiology 115, n^o 7 (1 octobre 2013) : 1015–24. http://dx.doi.org/10.1152/japplphysiol.00247.2013.

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The torque-velocity relationship has been widely considered as reflecting the mechanical properties of the contractile apparatus, and the influence of tendinous tissues on this relationship obtained during in vivo experiments remains to be determined. This study describes the pattern of shortening of various muscle-tendon unit elements of the triceps surae at different constant angular velocities and quantifies the contributions of fascicles, tendon, and aponeurosis to the global muscle-tendon unit shortening. Ten subjects performed isokinetic plantar flexions at different preset angular velocities (i.e., 30, 90, 150, 210, 270, and 330°/s). Ultrafast ultrasound measurements were performed on the muscle belly and on the myotendinous junction of the medial and lateral gastrocnemius muscles. The contributions of fascicles, tendon, and aponeurosis to global muscle-tendon unit shortening velocity were calculated for velocity conditions for four parts of the total range of motion. For both muscles, the fascicles' contribution decreased throughout the motion (73.5 ± 21.5% for 100–90° angular range to 33.7 ± 20.2% for 80–70°), whereas the tendon contribution increased (25.8 ± 15.4 to 55.6 ± 16.8%). In conclusion, the tendon contribution to the global muscle-tendon unit shortening is significant even during a concentric contraction. However, this contribution depends on the range of motion analyzed. The intersubject variability found in the maximal fascicle shortening velocity, for a given angular velocity, suggests that some subjects might possess a more efficient musculoarticular complex to produce the movement velocity. These findings are of great interest for understanding the ability of muscle-tendon shortening velocity.

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