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1.
PLoS One ; 15(10): e0240181, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33007014

RESUMO

OBJECTIVES: The purpose of this study was to compare the duration of high-intensity static stretching on flexibility and strength in the hamstrings. METHODS: Fourteen healthy males (20.8 ± 0.6 years, 170.7 ± 6.5 cm, 66.4 ± 9.9 kg) underwent high-intensity static stretching for three different durations (10, 15, and 20 seconds). The intensity of static stretching was set at the maximum point of discomfort. To examine the change in flexibility and strength, range of motion, peak passive torque, relative passive torque, muscle-tendon unit stiffness, peak torque of isokinetic knee flexion, and knee angle at peak torque of isokinetic knee flexion were measured. To evaluate a time course of pain, a numerical rating scale was described. RESULTS: Range of motion (P < 0.01), peak passive torque (P < 0.01), and knee angle at peak torque were increased at all interventions. Relative passive torque (P < 0.01) and muscle-tendon unit stiffness (P < 0.01) were decreased at all interventions. Peak torque decreased after 10 seconds of stretching (P < 0.05). Numerical rating scale during stretching was 8-9 levels in all interventions, the pain disappeared immediately after the post-measurements (median = 0). CONCLUSION: The results suggested that muscle-tendon unit stiffness decreased regardless of duration of high-intensity static stretching. However, peak torque of isokinetic knee flexion decreased after 10 seconds of high-intensity static stretching, though it was no change after for more than 15 seconds of stretching.


Assuntos
Músculos Isquiossurais/fisiologia , Exercícios de Alongamento Muscular , Feminino , Humanos , Articulação do Joelho/fisiologia , Masculino , Amplitude de Movimento Articular/fisiologia , Tendões/fisiologia , Torque
2.
Int J Nanomedicine ; 15: 6373-6383, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32904686

RESUMO

Background: The treatment of tendon injuries remains a challenging problem in clinical due to their slow and insufficient natural healing process. Scaffold-based tissue engineering provides a promising strategy to facilitate tendon healing and regeneration. However, many tissue engineering scaffolds have failed due to their poor and unstable mechanical properties. To address this, we fabricated nanofibrous polycaprolactone/methacrylated poly(trimethylene carbonate) (PCL/PTMC-MA) composite scaffolds via electrospinning. Materials and Methods: PTMC-MA was characterized by nuclear magnetic resonance. Fiber morphology of composite scaffolds was evaluated using scanning electron microscopy. The monotonic tensile test was performed for determining the mechanical properties of composite scaffolds. Cell viability and collagen deposition were assessed via PrestoBlue assay and enzyme-linked immunosorbent assay, respectively. Results: These PCL/PTMC-MA composite scaffolds had an increase in mechanical properties as PTMC-MA content increase. After photo-crosslinking, they showed further enhanced mechanical properties including creep resistance, which was superior to pure PCL scaffolds. It is worth noting that photo-crosslinked PCL/PTMC-MA (1:3) composite scaffolds had a Young's modulus of 31.13 ± 1.30 MPa and Max stress at break of 23.80 ± 3.44 MPa that were comparable with the mechanical properties of native tendon (Young's modulus 20-1200 MPa, max stress at break 5-100 MPa). In addition, biological experiments demonstrated that PCL/PTMC-MA composite scaffolds were biocompatible for cell adhesion, proliferation, and differentiation.


Assuntos
Células-Tronco Mesenquimais/citologia , Nanofibras/química , Fotoquímica/métodos , Tecidos Suporte/química , Animais , Adesão Celular , Diferenciação Celular , Proliferação de Células , Células Cultivadas , Colágeno/metabolismo , Dioxanos/química , Teste de Materiais , Camundongos Endogâmicos C57BL , Poliésteres/química , Polímeros/química , Regeneração , Tendões/fisiologia
3.
Proc Biol Sci ; 287(1933): 20200431, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32811308

RESUMO

Ground contact duration and stride frequency each affect muscle metabolism and help scientists link walking and running biomechanics to metabolic energy expenditure. While these parameters are often used independently, the product of ground contact duration and stride frequency (i.e. duty factor) may affect muscle contractile mechanics. Here, we sought to separate the metabolic influence of the duration of active force production, cycle frequency and duty factor. Human participants produced cyclic contractions using their soleus (which has a relatively homogeneous fibre type composition) at prescribed cycle-average ankle moments on a fixed dynamometer. Participants produced these ankle moments over short, medium and long durations while maintaining a constant cycle frequency. Overall, decreased duty factor did not affect cycle-average fascicle force (p ≥ 0.252) but did increase net metabolic power (p ≤ 0.022). Mechanistically, smaller duty factors increased maximum muscle-tendon force (p < 0.001), further stretching in-series tendons and shifting soleus fascicles to shorter lengths and faster velocities, thereby increasing soleus total active muscle volume (p < 0.001). Participant soleus total active muscle volume well-explained net metabolic power (r = 0.845; p < 0.001). Therefore, cyclically producing the same cycle-average muscle-tendon force using a decreased duty factor increases metabolic energy expenditure by eliciting less economical muscle contractile mechanics.


Assuntos
Metabolismo Energético/fisiologia , Músculo Esquelético/fisiologia , Tendões/fisiologia , Adulto , Tornozelo/fisiologia , Feminino , Marcha/fisiologia , Humanos , Masculino , Contração Muscular/fisiologia , Corrida/fisiologia , Caminhada/fisiologia
4.
Bone Joint J ; 102-B(8): 1095-1106, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32731821

RESUMO

AIMS: Achilles tendon injuries are a frequent problem in orthopaedic surgery due to their limited healing capacity and the controversy surrounding surgical treatment. In recent years, tissue engineering research has focused on the development of biomaterials to improve this healing process. The aim of this study was to analyze the effect of tendon augmentation with a nanostructured fibrin-agarose hydrogel (NFAH) or genipin cross-linked nanostructured fibrin-agarose hydrogel (GP-NFAH), on the healing process of the Achilles tendon in rats. METHODS: NFAH, GP-NFAH, and MatriDerm (control) scaffolds were generated (five in each group). A biomechanical and cell-biomaterial-interaction characterization of these biomaterials was then performed: Live/Dead Cell Viability Assay, water-soluble tetrazolium salt-1 (WST-1) assay, and DNA-released after 48 hours. Additionally, a complete section of the left Achilles tendon was made in 24 Wistar rats. Animals were separated into four treatment groups (six in each group): direct repair (Control), tendon repair with MatriDerm, or NFAH, or GP-NFAH. Animals were euthanized for further histological analyses after four or eight weeks post-surgery. The Achilles tendons were harvested and a histopathological analysis was performed. RESULTS: Tensile test revealed that NFAH and GP-NFAH had significantly higher overall biomechanical properties compared with MatriDerm. Moreover, biological studies confirmed a high cell viability in all biomaterials, especially in NFAH. In addition, in vivo evaluation of repaired tendons using biomaterials (NFAH, GP-NFAH, and MatriDerm) resulted in better organization of the collagen fibres and cell alignment without clinical complications than direct repair, with a better histological score in GP-NFAH. CONCLUSION: In this animal model we demonstrated that NFAH and GP-NFAH had the potential to improve tendon healing following a surgical repair. However, future studies are needed to determine the clinical usefulness of these engineered strategies. Cite this article: Bone Joint J 2020;102-B(8):1095-1106.


Assuntos
Tendão do Calcâneo/cirurgia , Microambiente Celular/efeitos dos fármacos , Colágeno/uso terapêutico , Elastina/uso terapêutico , Regeneração/efeitos dos fármacos , Traumatismos dos Tendões/cirurgia , Tendão do Calcâneo/lesões , Animais , Materiais Biocompatíveis/farmacologia , Modelos Animais de Doenças , Fibrina/farmacologia , Hidrogéis/farmacologia , Masculino , Nanoestruturas , Distribuição Aleatória , Ratos , Ratos Wistar , Tendões/fisiologia , Engenharia Tecidual/métodos , Cicatrização/efeitos dos fármacos , Cicatrização/fisiologia
5.
Int J Sports Med ; 41(11): 709-719, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32365388

RESUMO

This two-part narrative review aims to provide an insight into the age-related mechanical and neuromuscular factors contributing to: (1) decreased maximal muscle strength and power; (2) decreased force control; and (3) increased fatigability. Structural and functional changes from the macro-level of the muscle-tendon unit to the micro-level of the single muscle fibre have been reviewed and are described. At the muscle-tendon unit level, muscle volume, thickness and cross-sectional area, as well as pennation angle and fascicle length all decrease as part of the natural ageing process. These changes negatively affect muscle quality, muscle and tendon stiffness and Young's modulus and account for impairment in motor performance. A progressive age-related alteration in neuromuscular function is also well-established, with reduction in number and firing rate of the motor unit, contractile velocity and specific tension of muscle fibres, and stability of neuromuscular junction. These could be the result of structural alterations in the: (i) motor neuron, with number reduced, size and collateral sprouting increased; (ii) neuromuscular junction, with decreased post-synaptic junctional fold and density of active zones and increased pre-synaptic branching and post-synaptic area; and (iii) muscle fibre, with decreased number and size and increased type I and co-expression of myosin heavy chain.


Assuntos
Envelhecimento/fisiologia , Músculo Esquelético/fisiologia , Humanos , Neurônios Motores/citologia , Neurônios Motores/fisiologia , Fadiga Muscular/fisiologia , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/inervação , Junção Neuromuscular/anatomia & histologia , Junção Neuromuscular/fisiologia , Qualidade de Vida , Tendões/anatomia & histologia , Tendões/fisiologia
6.
J Sports Sci ; 38(13): 1516-1523, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32228117

RESUMO

Running is an activity with a consistently high injury rate. Running footwear design that mimics barefoot running has been proposed to reduce injury rate by increasing the strength of foot structures. However, there is little evidence to support this. The purpose of the current study is to use shear wave ultrasound elastography to examine material properties (shear modulus) of intrinsic foot structures in experienced minimally and traditionally shod runners. It is hypothesized that minimalist runners will exhibit increased stiffness compared to controls demonstrating the strengthening of these structures. Eighteen healthy runners (8 minimalist and 10 traditionalist), running a minimum of 10 mi · wk-1, participated. Elastography scans were performed on the left foot of each participant. There is no apparent stiffening of foot structures associated with wearing minimalist shoes. Only the FHB tendon is different between shoe types and, contrary to the hypothesis, was stiffer in traditionalist compared to minimalist runners (257.26 ± 51.64 kPa vs 160.88 ± 27.79 kPa, respectively). A moderate positive (r = 0.7) relationship between training load and tendon stiffness suggests strengthening of tendon when running in traditional shoes. If running in minimalist shoes increases loading on these structures without resulting in stronger tissues, it is possible that minimalist footwear may increase injury risk.


Assuntos
Técnicas de Imagem por Elasticidade , Pé/diagnóstico por imagem , Pé/fisiologia , Corrida/fisiologia , Sapatos , Adolescente , Adulto , Fenômenos Biomecânicos , Estudos Transversais , Módulo de Elasticidade , Desenho de Equipamento , Fáscia/diagnóstico por imagem , Fáscia/fisiologia , Análise da Marcha , Humanos , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Projetos Piloto , Fatores de Risco , Corrida/lesões , Tendões/diagnóstico por imagem , Tendões/fisiologia , Estudos de Tempo e Movimento , Adulto Jovem
7.
Sci Rep ; 10(1): 5872, 2020 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-32245985

RESUMO

Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon. Although plantar flexor muscle mechanics and Achilles tendon energy storage have been explored during rearfoot striking, they have not been fully characterized during forefoot striking. This study examined how plantar flexor muscle-tendon mechanics during running differs between rearfoot and forefoot striking. We used musculoskeletal simulations, driven by joint angles and electromyography recorded from runners using both rearfoot and forefoot striking running patterns, to characterize plantar flexor muscle-tendon mechanics. The simulations revealed that foot strike pattern affected the soleus and gastrocnemius differently. For the soleus, forefoot striking decreased tendon energy storage and fiber work done while the muscle fibers were shortening compared to rearfoot striking. For the gastrocnemius, forefoot striking increased muscle activation and fiber work done while the muscle fibers were lengthening compared to rearfoot striking. These changes in gastrocnemius mechanics suggest that runners planning to convert to forefoot striking might benefit from a progressive eccentric gastrocnemius strengthening program to avoid injury.


Assuntos
Músculo Esquelético/fisiologia , Corrida/fisiologia , Tendões/fisiologia , Tendão do Calcâneo/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Simulação por Computador , Eletromiografia , Feminino , , Humanos , Masculino , Fibras Musculares Esqueléticas/fisiologia , Fatores Sexuais
8.
Scand J Med Sci Sports ; 30(7): 1151-1162, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32246562

RESUMO

We mapped structural and functional characteristics of muscle-tendon units in a population exposed to very long-term routine overloading. Twenty-eight military academy cadets (age = 21.00 ± 1.1 years; height = 176.1 ± 4.8 cm; mass = 73.8 ± 7.0 kg) exposed for over 24 months to repetitive overloading were profiled via ultrasonography with a senior subgroup of them (n = 11; age = 21.4 ± 1.0 years; height = 176.5 ± 4.8 cm; mass = 71.4 ± 6.6 kg) also tested while walking and marching on a treadmill. A group of eleven ethnicity- and age-matched civilians (age = 21.6 ± 0.7 years; height = 176.8 ± 4.3 cm; mass = 74.6 ± 5.6 kg) was also profiled and tested. Cadets and civilians exhibited similar morphology (muscle and tendon thickness and cross-sectional area, pennation angle, fascicle length) in 26 out of 29 sites including the Achilles tendon. However, patellar tendon thickness along the entire tendon was greater (P < .05) by a mean of 16% for the senior cadets compared with civilians. Dynamically, cadets showed significantly smaller ranges of fascicle length change and lower shortening velocity in medial gastrocnemius during walking (44.0% and 47.6%, P < .05-.01) and marching (27.5% and 34.3%, P < .05-.01) than civilians. Furthermore, cadets showed lower normalized soleus electrical activity during walking (22.7%, P < .05) and marching (27.0%, P < .05). Therefore, 24-36 months of continuous overloading, primarily occurring under aerobic conditions, leads to more efficient neural and mechanical behavior in the triceps surae complex, without any major macroscopic alterations in key anatomical structures.


Assuntos
Militares , Músculo Esquelético/fisiologia , Tendões/fisiologia , Caminhada , Fenômenos Biomecânicos , Humanos , Masculino , Ultrassonografia , Adulto Jovem
9.
Am J Ophthalmol ; 216: 186-192, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32247775

RESUMO

PURPOSE: Magnetic resonance imaging was used to determine the effect of axial length (AL) on globe rotational axis and horizontal extraocular muscle leverage during horizontal duction. DESIGN: Prospective observational case series. METHODS: At a single academic center, 36 orthophoric adults with a wide range of ALs underwent high-resolution axial orbital magnetic resonance imaging in target-controlled adduction and abduction. ALs were measured in planes containing maximum globe cross-sections. Area centroids were calculated to determine globe centers. Rotational axes in orbital coordinates were calculated from displacements of lens centers and globe-optic nerve attachments. Lever arms were calculated as distances between published extraocular muscle insertions and rotational axes. RESULTS: ALs averaged 26.3 ± 0.3 mm (standard error [range 21.5-33.4 mm]). Rotational axes from adduction to abduction averaged 1.1 ± 0.2 mm medial and 1.1 ± 0.2 mm anterior to the globe's geometric center in adduction. Linear regression demonstrated no significant correlation between AL and rotational axis horizontal (R2 = 0.06) or anteroposterior (R2 = 0.07) position. Medial rectus (MR) lever arms averaged 12.0 ± 0.2 mm and lateral rectus (LR) lever arms averaged 12.8 ± 0.2 mm. Both MR (R2 = 0.24, P < .001) and LR (R2 = 0.32, P < .001) lever arms significantly increased by about 0.3 mm per 1.0-mm of increased AL, with a corresponding reduction in predicted per-millimeter effect of surgical repositioning of their insertions. CONCLUSIONS: Regardless of AL, the globe rotates about a point nasal and anterior to its geometric center, giving the LR more leverage than the MR. This eccentricity may diminish the effect of tendon repositioning in moderate to highly myopic patients, with reductions in per-mill imeter dose/response predicted with longer AL.


Assuntos
Comprimento Axial do Olho/anatomia & histologia , Movimentos Oculares/fisiologia , Músculos Oculomotores/fisiologia , Tendões/fisiologia , Adulto , Idoso , Comprimento Axial do Olho/diagnóstico por imagem , Feminino , Voluntários Saudáveis , Humanos , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Músculos Oculomotores/diagnóstico por imagem , Estudos Prospectivos
10.
Sci Rep ; 10(1): 3992, 2020 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-32132649

RESUMO

Tendons are dense fibrous structures that attach muscles to bones. Healing of tendon injuries is a clinical challenge owing to poor regenerative potential and scarring. Here, we created reporter mice that express EGFP, driven by the promoter of the tendon-specific Scleraxis (Scx) transcription-factor gene; we then generated induced pluripotent stem cells (iPSCs) from these mice. Utilising these fluorescently labelled iPSCs, we developed a tenogenic differentiation protocol. The iPSC-derived EGFP-positive cells exhibited elevated expression of tendon-specific genes, including Scx, Mohawk, Tenomodulin, and Fibromodulin, indicating that they have tenocyte-like properties. Finally, we demonstrated that these cells promoted tendon regeneration in mice after transplantation into injured tendons reducing scar formation via paracrine effect. Our data demonstrate that the tenogenic differentiation protocol successfully provided functional cells from iPSCs. We propose that pluripotent stem cell-based therapy using this protocol will provide an effective therapeutic approach for tendon injuries.


Assuntos
Células-Tronco Pluripotentes Induzidas/metabolismo , Regeneração , Traumatismos dos Tendões/metabolismo , Tendões/fisiologia , Tenócitos/metabolismo , Animais , Antígenos de Diferenciação/biossíntese , Regulação da Expressão Gênica , Camundongos , Camundongos Transgênicos , Traumatismos dos Tendões/genética
11.
J Sports Sci Med ; 19(1): 52-58, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32132827

RESUMO

While the time course of muscle-tendon unit (MTU) function and structure following short (1 min) and long (5 min) durations of static stretching has already been investigated, less is known about medium stretch durations. Therefore, the purpose of this study was to investigate the time course of these parameters following 3 min of static stretching of the plantar flexor muscles. Fourteen healthy volunteers were tested on two separate days in a random order with two different rest times (0 min, 5 min) after 3 × 60 s of stretching. During each test, the dorsiflexion range of motion (RoM), passive resistive torque (PRT), and maximum voluntary contraction (MVC) were measured with a dynamometer. Ultrasonography of the gastrocnemius medialis (GM) muscle-tendon junction displacement and motion capture allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate their stiffness. We observed an increase in RoM and a decrease in PRT and muscle-tendon stiffness at 0 min and 5 min post-stretching. This can be attributed to a decrease in muscle stiffness, as a decrease in PRT and muscle stiffness was observed up to 5 min after the stretching. No changes were detected in MVC torque and tendon stiffness. Static stretching for 3 × 60 s changes the muscle-tendon functions (RoM, PRT) for at least 5 min. These changes are related to mechano-morphological changes of the muscle, but not the tendon structure.


Assuntos
Exercícios de Alongamento Muscular , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/fisiologia , Tendões/anatomia & histologia , Tendões/fisiologia , Adulto , Eletromiografia , Feminino , Humanos , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/diagnóstico por imagem , Amplitude de Movimento Articular/fisiologia , Tendões/diagnóstico por imagem , Fatores de Tempo , Torque , Ultrassonografia , Adulto Jovem
12.
Nat Commun ; 11(1): 1332, 2020 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-32165612

RESUMO

Compared to transmission systems based on shafts and gears, tendon-driven systems offer a simpler and more dexterous way to transmit actuation force in robotic hands. However, current tendon fibers have low toughness and suffer from large friction, limiting the further development of tendon-driven robotic hands. Here, we report a super tough electro-tendon based on spider silk which has a toughness of 420 MJ/m3 and conductivity of 1,077 S/cm. The electro-tendon, mechanically toughened by single-wall carbon nanotubes (SWCNTs) and electrically enhanced by PEDOT:PSS, can withstand more than 40,000 bending-stretching cycles without changes in conductivity. Because the electro-tendon can simultaneously transmit signals and force from the sensing and actuating systems, we use it to replace the single functional tendon in humanoid robotic hand to perform grasping functions without additional wiring and circuit components. This material is expected to pave the way for the development of robots and various applications in advanced manufacturing and engineering.


Assuntos
Condutividade Elétrica , Seda/química , Aranhas/química , Tendões/fisiologia , Animais , Simulação por Computador , Retroalimentação , Humanos , Teste de Materiais , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestrutura , Impressão Tridimensional , Robótica , Seda/ultraestrutura
13.
Integr Comp Biol ; 60(1): 140-155, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32211841

RESUMO

The geometry of the musculoskeletal system, such as moment arms and linkages, determines the link between muscular functions and external mechanical results, but as the geometry becomes more complex, this link becomes less clear. The musculoskeletal system of snakes is extremely complex, with several muscles that span dozens of vertebrae, ranging from 10 to 45 vertebrae in the snake semispinalis-spinalis muscle (a dorsiflexor). Furthermore, this span correlates with habitat in Caenophidians, with burrowing and aquatic species showing shorter spans while arboreal species show longer spans. Similar multi-articular spans are present in the prehensile tails of primates, the necks of birds, and our own digits. However, no previous analysis has adequately explained the mechanical consequences of these multi-articular spans. This paper uses techniques from the analysis of static systems in engineering to analyze the consequences of multiarticular muscle configurations in cantilevered gap bridging and compares these outcomes to a hypothetical mono-articular system. Multi-articular muscle spans dramatically reduce the forces needed in each muscle, but the consequent partitioning of muscle cross-sectional area between numerous muscles results in a small net performance loss. However, when a substantial fraction of this span is tendinous, performance increases dramatically. Similarly, metabolic cost is increased for purely muscular multi-articular spans, but decreases rapidly with increasing tendon ratio. However, highly tendinous spans require increased muscle strain to achieve the same motion, while purely muscular systems are unaffected. These results correspond well with comparative data from snakes and offer the potential to dramatically improve the mechanics of biomimetic snake robots.


Assuntos
Locomoção/fisiologia , Músculo Esquelético/fisiologia , Serpentes/fisiologia , Tendões/fisiologia , Animais , Fenômenos Biomecânicos
14.
Gait Posture ; 77: 89-94, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32004951

RESUMO

BACKGROUND: Reduced push-off intensity during walking is thought to play an important role in age-related mobility impairment. We posit that an age-related shift toward shorter plantarflexor operating lengths during walking functionally limits force generation, and thereby the ability of those muscles to respond to increased propulsive demands during walking. RESEARCH QUESTION: To determine whether gastrocnemius muscle fascicle lengths during normal walking: (1) are shorter in older than young adults, and (2) correlate with one's capacity to increase the propulsive demands of walking to their maximum. METHODS: We used in vivo cine B-mode ultrasound to measure gastrocnemius fascicle lengths in 9 older and 9 young adults walking at their preferred speed, their maximum speed, and with horizontal impeding forces that increased in a ramped design at 1%BW/s to their maximum. A repeated measures ANOVA tested for effects of age and walking condition, and Pearson correlations assessed the relation between fascicle outcomes and condition performance. RESULTS: A tendency toward shorter medial gastrocnemius muscle fascicle lengths in older versus young adults was not statistically significant. However, older adults walked with reduced peak fascicle shortening during all conditions compared to young adults - an outcome not explained by reduced muscle-tendon unit shortening and exacerbated during tasks with greater than normal propulsive demand. As hypothesized, we found a strong and significant positive correlation in older subjects between gastrocnemius fascicle lengths during normal walking and performance on the ramped impeding force condition (p = 0.005, r²â€¯= 0.704), even after controlling for isometric strength (p = 0.011, r²â€¯= 0.792) and subject stature (p = 0.010, r²â€¯= 0.700). SIGNIFICANCE: Our findings provide muscle-level insight to develop more effective rehabilitation techniques to improve push-off intensity in older adults and assistive technologies designed to steer plantarflexor muscle fascicle operating behavior during functional tasks.


Assuntos
Marcha/fisiologia , Perna (Membro)/diagnóstico por imagem , Músculo Esquelético/diagnóstico por imagem , Adulto , Fatores Etários , Idoso , Fenômenos Biomecânicos , Feminino , Humanos , Perna (Membro)/fisiologia , Perna (Membro)/fisiopatologia , Masculino , Músculo Esquelético/fisiologia , Músculo Esquelético/fisiopatologia , Equipamentos de Autoajuda , Tendões/fisiologia , Ultrassonografia , Caminhada/fisiologia , Adulto Jovem
15.
Bone Joint J ; 102-B(2): 205-211, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32009424

RESUMO

AIMS: To evaluate the donor site morbidity and tendon morphology after harvesting whole length, full-thickness peroneus longus tendon (PLT) proximal to the lateral malleolus for ligament reconstructions or tendon transfer. METHODS: A total of 21 eligible patients (mean age 34.0 years (standard deviation (SD) 11.2); mean follow-up period 31.8 months (SD 7.7), and 12 healthy controls (mean age, 26.8 years (SD 5.9) were included. For patients, clinical evaluation of the donor ankle was performed preoperatively and postoperatively. Square hop test, ankle strength assessment, and MRI of distal calf were assessed bilaterally in the final follow-up. The morphological symmetry of peroneal tendons bilaterally was evaluated by MRI in healthy controls. RESULTS: Among the patients, the mean pre- and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score and Karlsson-Peterson score were 98.7 (SD 2.5; p = 0.480) and 98.5 (SD 2.4; p = 0.480), and 98.3 (SD 2.4; p = 0.162) and 97.9 (SD 2.5; p = 0.162), respectively. There was no significant difference between square hop test bilaterally (p = 0.109) and plantar flexion peak force bilaterally (p = 0.371). The harvested limb had significantly less eversion peak force compared to the contralateral limb (p < 0.001). Evidence of probable tendon regeneration was observed in all the patients by MRI and the total bilateral peroneal tendon index (mean ratio of harvested side cross-sectional area of peroneal tendon compared with the contralateral side) was 82.9% (SD 17.4). In 12 healthy controls, peroneal tendons (mean 99.4% (SD 4.3) were found to be morphologically symmetrical between the two sides. CONCLUSION: The current study showed satisfactory clinical foot and ankle outcomes after full-thickness PLT harvesting and indicated the regenerative potential of PLT after its removal. Level of Evidence: Level IV, therapeutic retrospective case series. Cite this article: Bone Joint J 2020;102-B(2):205-211.


Assuntos
Articulação do Tornozelo/fisiopatologia , Tornozelo/fisiopatologia , Pé/fisiopatologia , Ligamentos Articulares/fisiopatologia , Tendões/transplante , Sítio Doador de Transplante/fisiopatologia , Adulto , Tornozelo/diagnóstico por imagem , Articulação do Tornozelo/diagnóstico por imagem , Feminino , Pé/diagnóstico por imagem , Humanos , Ligamentos Articulares/cirurgia , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Procedimentos Cirúrgicos Reconstrutivos , Recuperação de Função Fisiológica , Regeneração , Estudos Retrospectivos , Transferência Tendinosa , Tendões/diagnóstico por imagem , Tendões/fisiologia , Coleta de Tecidos e Órgãos/métodos , Coleta de Tecidos e Órgãos/reabilitação , Sítio Doador de Transplante/diagnóstico por imagem , Transplante Autólogo , Resultado do Tratamento , Adulto Jovem
16.
Comput Methods Biomech Biomed Engin ; 23(6): 213-223, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31958016

RESUMO

In this paper, we characterized the hyperelastic and damage behavior of the Extensor Digitorum Longus (EDL) human tendon under loading conditions. The study was conducted in both categories of models, phenomenological and physically motivated, to allow the prediction and the macroscopic response of the tendon under specific loading conditions, assuming that its response follows a hyperelastic anisotropic model in conjunction with damage law. We benchmarked multiple hyperelastic and damage models to fit the response of the tendons in uniaxial tensile loading conditions, and by employing a genetic algorithm, we obtained the material parameters for both elastic and damage models. The objective of this study was to explore different mathematical models to determine which would be the best option to predict the behavior of tendons and ligaments in complex biological systems using Finite Elements (FE) models. Therefore, we took into account accuracy as well as computational features. We considered the model proposed by Shearer and coupled it with a sigmoid function, which governs the evolution of damage in tendons, as the most appropriate for the fitting of the experimental data. The achieved solution shows to be of high interest attributable to the simplicity of the damage law function and its low computational cost.


Assuntos
Elasticidade , Tendões/fisiologia , Algoritmos , Anisotropia , Humanos , Modelos Biológicos , Estresse Mecânico
17.
Int J Biol Macromol ; 147: 24-28, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31904464

RESUMO

Nanoparticles owing to their size have a substantial influence on the biological behavior of collagen, thereby opening new channels to unfold the propensity of nanoparticles in terms of collagen stabilization. The present study aims to synthesize and characterize cerium oxide nanoparticles and to investigate their crosslinking efficiency on collagen. Cerium oxide nanoparticles, known biocatalysts, form an effective oxidation system due to their variable oxidation state. Ionic liquid functionalizes cerium oxide nanoparticles (IL-CONP) have been synthesis by the sonication method and characterizes using techniques such as Dynamic Light Scattering, and X-ray Diffraction. The hydrodynamic diameter, Zeta potential and polydispersity index of nanoparticles is 192.3 ± 2.14 nm, -13.76 ± 1.5 mV and 0.387, respectively. Changes in the secondary structure of collagen upon treatment with increasing concentration of IL-CONP indicate conformational modifications at the molecular level. Differential scanning calorimetry studies on rat tail tendon collagen fibers with IL-CONP indicate an increase in thermal stability of collagen from 61 to 87 °C. Thus, cerium oxide-based nanoparticle crosslinking invokes a considerable array of interest as a potential crosslinking agent for collagen.


Assuntos
Cério/química , Colágeno/química , Líquidos Iônicos/química , Nanopartículas/química , Animais , Varredura Diferencial de Calorimetria , Dicroísmo Circular , Tamanho da Partícula , Estabilidade Proteica , Estrutura Secundária de Proteína , Ratos Wistar , Espectroscopia de Infravermelho com Transformada de Fourier , Cauda , Temperatura , Tendões/fisiologia , Difração de Raios X
18.
Eur J Appl Physiol ; 120(3): 653-664, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31980900

RESUMO

PURPOSE: The twofold purpose of this study was (1) to compare differences in development and etiology of neuromuscular fatigue at different plantar flexor (PF) muscle-tendon unit (MTU) lengths between boys and men, and (2) to examine the relationship between musculotendinous stiffness and peripheral fatigue. METHODS: Nineteen pre-pubertal boys and 23 men performed three intermittent fatigue protocols at different PF MTU lengths (short: S, neutral: N and long: L), consisting of repeating maximal voluntary isometric contractions (MVIC) until the torque reached 60% of the initial value of MVIC. The etiology of the neuromuscular fatigue and the gastrocnemius medialis aponeuroses and tendon stiffness (KGM) were investigated using non-invasive methods. RESULT: The number of repetitions did not differ between men and boys, regardless of the PF MTU length (S: 16.5 ± 5.4 and 17.6 ± 5.8; N: 15.8 ± 4.5 and 13.3 ± 3.6; L: 13.6 ± 4.8 and 12.6 ± 4.6, respectively). Boys displayed a lower decrement of potentiated twitch torque (Qtwpot; p < 0.001) and greater decrease of voluntary activation level than men (p < 0.001). Although boys showed lower KGM values than men at S, no significant correlation was found between KGM and Qtwpot. CONCLUSION: PF MTU length had no effect on differences in the development and etiology of neuromuscular fatigue between boys and men. Although both groups displayed similar development of fatigue, central mechanisms mainly accounted for fatigue in boys and peripheral mechanisms were mainly involved in men. Additionally, musculotendinous stiffness did not account for difference in peripheral fatigue between children and adults.


Assuntos
Envelhecimento/fisiologia , Fadiga Muscular , Músculo Esquelético/fisiologia , Tendões/fisiologia , Adolescente , Aponeurose/fisiologia , Criança , Humanos , Contração Isométrica , Masculino , Torque , Adulto Jovem
19.
Clin Neurophysiol ; 131(1): 160-166, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31794957

RESUMO

OBJECTIVE: When the compound muscle action potential (CMAP) is recorded in motor nerve conduction studies, the reference (E2) electrode can make a significant contribution to the CMAP. This study investigates the E2 recorded signal and its effect on CMAP measurements when E2 electrode is placed at different sites. METHODS: The CMAP was recorded using the active electrode on the muscle belly and 4 different E2 electrodes placed at distal and proximal sites. The signal recorded by each electrode was also measured using a reference electrode on the contralateral limb. Signals were recorded from the abductor pollicis brevis, abductor digiti minimi, tibialis anterior and biceps muscles. RESULTS: The E2 recorded a smaller signal when it was placed near or off the proximal tendon or muscle origin. This affected CMAP latency, duration for tibialis anterior. Contrary to expectation, initial upward deflection was noted for E2 signal. CONCLUSION: A proximal E2 position records a lower volume conducted signal and yields a CMAP that is more representative of the muscle over which the E1 (active) electrode is placed. SIGNIFICANCE: The proposed 'Proximal E2' montage may be better suited to assess pathology.


Assuntos
Potenciais de Ação/fisiologia , Eletrodos , Neurônios Motores/fisiologia , Músculo Esquelético/fisiologia , Condução Nervosa/fisiologia , Adulto , Idoso , Eletrodos/normas , Eletromiografia/instrumentação , Eletromiografia/métodos , Feminino , Humanos , Masculino , Nervo Mediano/fisiologia , Pessoa de Meia-Idade , Músculo Esquelético/anatomia & histologia , Nervo Musculocutâneo/fisiologia , Nervo Fibular/fisiologia , Estatísticas não Paramétricas , Tendões/fisiologia , Nervo Ulnar/fisiologia
20.
Eur J Appl Physiol ; 120(1): 203-217, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31776693

RESUMO

PURPOSE: Muscle-tendon units are forcefully stretched during rapid deceleration events such as landing. Consequently, tendons act as shock absorbers by buffering the negative work produced by muscle fascicles likely to prevent muscle damage. Landing surface properties can also modulate the amount of energy dissipated by the body, potentially effecting injury risk. This study aimed to evaluate the influence of three different surfaces on the muscle-tendon interactions of gastrocnemius medialis (GM), and vastus lateralis (VL) during single- and double-leg landings from 50 cm. METHODS: Ultrasound images, muscle activity and joint kinematics were collected for 12 participants. Surface testing was also performed, revealing large differences in mechanical behavior. RESULTS: During single-leg landing, stiffer surfaces increased VL fascicle lengthening and velocity, and muscle activity independent of joint kinematics while GM length changes showed no difference between surfaces. Double-leg landing resulted in similar fascicle and tendon behavior despite greater knee flexion angles on stiffer surfaces. CONCLUSION: This demonstrates that VL fascicle lengthening is greater when the surface stiffness increases, when performing single-leg landing. This is due to the combination of limited knee joint flexion and lower surface absorption ability which resulted in greater mechanical demand mainly withstood by fascicles. GM muscle-tendon interactions remain similar between landing surfaces and types. Together, this suggests that surface damping properties primarily affect the VL muscle-tendon unit with a potentially higher risk of injury as a result of increased surface stiffness when performing single-leg landing tasks.


Assuntos
Músculo Quadríceps/fisiologia , Tendões/fisiologia , Adulto , Fenômenos Biomecânicos , Humanos , Perna (Membro)/fisiologia , Masculino , Movimento , Músculo Quadríceps/diagnóstico por imagem , Propriedades de Superfície , Tendões/diagnóstico por imagem
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