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PloS One 2018Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to... (Clinical Trial)
Clinical Trial
Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 ± 3.0 y, 90.0 ± 13.8 kg, 174.9 ± 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscle's length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3-5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d ∙ wk-1) of training (POST). Although three-way (muscle [RF, VL] x region [30, 50, 70%] x time [PRE, POST]) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 ± 0.69 cm2, p < 0.001) over the RF (0.59 ± 0.20 cm2, p = 0.011), while significant decreases in average FL were noted for the RF (-1.03 ± 0.30 cm, p = 0.004) but not the VL (-0.05 ± 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.
Topics: Adaptation, Physiological; Adult; Exercise; Humans; Male; Muscle Strength; Muscle, Skeletal; Quadriceps Muscle; Resistance Training; Young Adult
PubMed: 30161137
DOI: 10.1371/journal.pone.0198304 -
Clinical Orthopaedics and Related... Apr 2020Children with cerebral palsy have impaired muscle growth and muscular contractures that limit their ROM. Contractures have a decreased number of serial sarcomeres and...
BACKGROUND
Children with cerebral palsy have impaired muscle growth and muscular contractures that limit their ROM. Contractures have a decreased number of serial sarcomeres and overstretched lengths, suggesting an association with a reduced ability to add the serial sarcomeres required for normal postnatal growth. Contractures also show a markedly reduced number of satellite cells-the muscle stem cells that are indispensable for postnatal muscle growth, repair, and regeneration. The potential role of the reduced number of muscle stem cells in impaired sarcomere addition leading to contractures must be evaluated.
QUESTIONS/PURPOSES
(1) Does a reduced satellite cell number impair the addition of serial sarcomeres during recovery from an immobilization-induced contracture? (2) Is the severity of contracture due to the decreased number of serial sarcomeres or increased collagen content?
METHODS
The hindlimbs of satellite cell-specific Cre-inducible mice (Pax7; Rosa26; n = 10) were maintained in plantarflexion with plaster casts for 2 weeks so that the soleus was chronically shortened and the number of its serial sarcomeres was reduced by approximately 20%. Subsequently, mice were treated with either tamoxifen to reduce the number of satellite cells or a vehicle (an injection and handling control). The transgenic mouse model with satellite cell ablation combined with a casting model to reduce serial sarcomere number recreates two features observed in muscular contractures in children with cerebral palsy. After 30 days, the casts were removed, the mice ankles were in plantarflexion, and the mice's ability to recover its ankle ROM by cage remobilization for 30 days were evaluated. We quantified the number of serial sarcomeres, myofiber area, and collagen content of the soleus muscle as well as maximal ankle dorsiflexion at the end of the recovery period.
RESULTS
Mice with reduced satellite cell numbers did not regain normal ankle ROM in dorsiflexion; that is, the muscles remained in plantarflexion contracture (-16° ± 13° versus 31° ± 39° for the control group, -47 [95% confidence interval -89 to -5]; p = 0.03). Serial sarcomere number of the soleus was lower on the casted side than the contralateral side of the mice with a reduced number of satellite cells (2214 ± 333 versus 2543 ± 206, -329 [95% CI -650 to -9]; p = 0.04) but not different in the control group (2644 ± 194 versus 2729 ± 249, -85 [95% CI -406 to 236]; p = 0.97). The degree of contracture was strongly associated with the number of sarcomeres and myofiber area (r =0.80; P < 0.01) rather than collagen content. No differences were seen between groups in terms of collagen content and the fraction of muscle area.
CONCLUSIONS
We found that a reduced number of muscle stem cells in a transgenic mouse model impaired the muscle's ability to add sarcomeres in series and thus to recover from an immobilization-induced contracture.
CLINICAL RELEVANCE
The results of our study in transgenic mouse muscle suggests there may be a mechanistic relationship between a reduced number of satellite cells and a reduced number of serial sarcomeres. Contracture development, secondary to impaired sarcomere addition in muscles in children with cerebral palsy may be due to a reduced number of muscle stem cells.
Topics: Animals; Cerebral Palsy; Contracture; Disease Models, Animal; Hindlimb; Mice; Mice, Transgenic; Muscle, Skeletal; Range of Motion, Articular; Sarcomeres; Stem Cells; Tamoxifen
PubMed: 32011372
DOI: 10.1097/CORR.0000000000001134 -
The International Journal of... Mar 1990In the present study we focused our attention on the role of spinal cord-muscle interactions in the development of muscle and spinal cord cells. Four experimental... (Review)
Review
In the present study we focused our attention on the role of spinal cord-muscle interactions in the development of muscle and spinal cord cells. Four experimental approaches were used: 1) muscle fiber-spinal cord co-culture; 2) chronic spinal cord stimulation in chick embryos; 3) direct electrical stimulation of the denervated chick muscle; 4) skeletal muscle transplantation in close apposition to the spinal cord in chick embryos. The characteristics of mATPase and energetic metabolism enzyme activities and of myosin isoform expression were used as markers for fiber types in two peculiar muscles, the fast-twitch PLD and the slow-tonic ALD. In vitro, in the absence of neurons, myoblasts can express some characteristics of either slow or fast muscle types according to their origin, while in the presence of neurons, muscle fiber differentiation seems to be related to the spontaneous rhythm delivered by the neurons. The in ovo experiments of chronic spinal cord stimulation demonstrate that the differentiation of the fast and slow muscle features appears to be rhythm dependent. In the chick, direct stimulation of denervated muscles shows that the rhythm of the muscle activity is also involved in the control of muscle properties. In chick embryos developing ALD, the changes induced by modifications of muscle tension demonstrate that this factor also influences muscle development. Other experiments show that muscle back-transplantation can alter the early spinal cord development.
Topics: Aging; Animals; Cell Communication; Cells, Cultured; Chick Embryo; Chickens; Embryo, Nonmammalian; Motor Neurons; Muscle Development; Muscles; Quail; Spinal Cord
PubMed: 2203457
DOI: No ID Found -
Progress in Biophysics and Molecular... Nov 2017Discovery of Piezo channels and the reporting of their sensitivity to the inhibitor GsMTx4 were important milestones in the study of non-selective cationic... (Review)
Review
Discovery of Piezo channels and the reporting of their sensitivity to the inhibitor GsMTx4 were important milestones in the study of non-selective cationic mechanosensitive channels (MSCs) in normal physiology and pathogenesis. GsMTx4 had been used for years to investigate the functional role of cationic MSCs, especially in muscle tissue, but with little understanding of its target or inhibitory mechanism. The sensitivity of Piezo channels to bilayer stress and its robust mechanosensitivity when expressed in heterologous systems were keys to determining GsMTx4's mechanism of action. However, questions remain regarding Piezo's role in muscle function due to the non-selective nature of GsMTx4 inhibition toward membrane mechanoenzymes and the implication of MCS channel types by genetic knockdown. Evidence supporting Piezo like activity, at least in the developmental stages of muscle, is presented. While the MSC targets of GsMTx4 in muscle pathology are unclear, its muscle protective effects are clearly demonstrated in two recent in situ studies on normal cardiomyocytes and dystrophic skeletal muscle. The muscle protective function may be due to the combined effect of GsMTx4's inhibitory action on cationic MSCs like Piezo and TRP, and its potentiation of repolarizing K selective MSCs like K2P and SAKCa. Paradoxically, the potent in vitro action of GsMTx4 on many physiological functions seems to conflict with its lack of in situ side-effects on normal animal physiology. Future investigations into cytoskeletal control of sarcolemma mechanics and the suspected inclusion of MSCs in membrane micro/nano sized domains with distinct mechanical properties will aide our understanding of this dichotomy.
Topics: Animals; Electrophysiological Phenomena; Humans; Ion Channel Gating; Ion Channels; Mechanical Phenomena; Muscles
PubMed: 28778608
DOI: 10.1016/j.pbiomolbio.2017.07.011 -
Journal of Applied Physiology... Mar 2019Most limb muscles operate within a compartment defined by fascial layers that enclose a muscle or groups of muscles within a defined space. These compartments are...
Most limb muscles operate within a compartment defined by fascial layers that enclose a muscle or groups of muscles within a defined space. These compartments are important clinically, because fluid accumulation can cause ischemia and tissue necrosis if untreated. Little is known, however, about how fascial enclosures influence healthy muscle function. One previous study showed that removing a fascial covering reduced the force output of a muscle under maximal stimulation. We hypothesized that such reduction in force output was due to a change in the muscle length following fasciotomy and that a reduced force output could be explained by the length-tension relationship of muscle. Thus we predicted that the maximum force across a range of lengths would be unchanged following fasciotomy. We measured maximal tetanic force output in a wing muscle in wild turkeys both before and after removal of fascia that enclosed the muscle in a compartment. Our hypothesis was not supported. The length-tension curve of this muscle showed that removal of fascia reduced maximum force output to 72 ± 10% of the prefascial release condition. Thus a reduction in muscle force following fasciotomy was not explained by a change in muscle length. The mechanism underlying reduction in force is unclear, but it suggests that the assumption underlying most isolated muscle experiments, i.e., removal of a muscle from its situation in vivo does not influence its maximal mechanical output, may need reexamining. NEW & NOTEWORTHY Most limb muscles are enclosed within compartments bound by robust fascial sheets. The mechanical significance of the close packing of muscle and fascia is largely unexplored. We used an animal model to show that removal of a fascial covering reduces the maximal force developed during contraction. These results raise questions about the use of isolated muscles to estimate muscle performance and suggest that a muscle's mechanical surrounding influences performance by mechanisms that are not understood.
Topics: Animals; Biomechanical Phenomena; Birds; Fascia; Fasciotomy; Female; Male; Mechanical Phenomena; Muscle Contraction; Muscle, Skeletal
PubMed: 30543496
DOI: 10.1152/japplphysiol.00330.2018 -
Sensors (Basel, Switzerland) Nov 2023This work presents the fabrication and characterization of a triple-layered biomimetic muscle constituted by polypyrrole (PPy)-dodecylbenzenesulfonate (DBS)/adhesive...
This work presents the fabrication and characterization of a triple-layered biomimetic muscle constituted by polypyrrole (PPy)-dodecylbenzenesulfonate (DBS)/adhesive tape/PPy-DBS demonstrating simultaneous sensing and actuation capabilities. The muscle was controlled by a neurobiologically inspired cortical neural network sending agonist and antagonist signals to the conducting polymeric layers. Experiments consisted of controlled voluntary movements of the free end of the muscle at angles of ±20°, ±30°, and ±40° while monitoring the muscle's potential response. Results show the muscle's potential varies linearly with applied current amplitude during actuation, enabling current sensing. A linear dependence between muscle potential and temperature enabled temperature sensing. Electrolyte concentration changes also induced exponential variations in the muscle's potential, allowing for concentration sensing. Additionally, the influence of the electric current density on the angular velocity, the electric charge density, and the desired angle was studied. Overall, the conducting polymer-based soft biomimetic muscle replicates properties of natural muscles, permitting simultaneous motion control, current, temperature, and concentration sensing. The integrated neural control system exhibits key features of biological motion regulation. This muscle actuator with its integrated sensing and control represents an advance for soft robotics, prosthetics, and biomedical devices requiring biomimetic multifunctionality.
Topics: Polymers; Biomimetics; Robotics; Pyrroles; Muscles
PubMed: 38005519
DOI: 10.3390/s23229132 -
Integrative and Comparative Biology Aug 2018Muscles undergo cycles of length change and force development during locomotion, and these contribute to their work and power production to drive body motion. Muscle...
Muscles undergo cycles of length change and force development during locomotion, and these contribute to their work and power production to drive body motion. Muscle fibers are typically considered to be linear actuators whose stress depends on their length, velocity, and activation state, and whose properties can be scaled up to explain the function of whole muscles. However, experimental and modeling studies have shown that a muscle's stress additionally depends on inactive and passive tissues within the muscle, the muscle's size, and its previous contraction history. These effects have not been tested under common sets of contraction conditions, especially the cyclic contractions that are typical of locomotion. Here we evaluate the relative effects of size, history-dependent, activation and three-dimensional effects on the work and power produced during cyclic contractions of muscle models. Simulations of muscle contraction were optimized to generate high power outputs: this resulted in the muscle models being largely active during shortening, and inactive during lengthening. As such, the history-dependent effects were dominated by force depression during simulated active shortening rather than force enhancement during active stretch. Internal work must be done to deform the muscle tissue, and to accelerate the internal muscle mass, resulting in reduced power and work that can be done on an external load. The effect of the muscle mass affects the scaling of muscle properties, with the inertial costs of contraction being relatively greater at larger sizes and lower activation levels.
Topics: Animals; Biomechanical Phenomena; Humans; Locomotion; Muscle Contraction; Muscle, Skeletal
PubMed: 29726964
DOI: 10.1093/icb/icy021 -
PloS One 2013Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive,...
Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive, significantly increase the risk of chronic diseases. The purpose of this study was to provide details of quadriceps and hamstring muscle inactivity and activity during normal daily life of ordinary people. Eighty-four volunteers (44 females, 40 males, 44.1±17.3 years, 172.3±6.1 cm, 70.1±10.2 kg) were measured during normal daily life using shorts measuring muscle electromyographic (EMG) activity (recording time 11.3±2.0 hours). EMG was normalized to isometric MVC (EMG(MVC)) during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5±1.7% of EMG(MVC)). During normal daily life the average EMG amplitude was 4.0±2.6% and average activity burst amplitude was 5.8±3.4% of EMG(MVC) (mean duration of 1.4±1.4 s) which is below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC)). Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5±11.9% of the total recording time and the longest inactivity periods lasted for 13.9±7.3 min (2.5-38.3 min). Women had more activity bursts and spent more time at intensities above 40% EMG(MVC) than men (p<0.05). In conclusion, during normal daily life the locomotor muscles are inactive about 7.5 hours, and only a small fraction of muscle's maximal voluntary activation capacity is used averaging only 4% of the maximal recruitment of the thigh muscles. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting by standing can considerably increase cumulative daily muscle activity.
Topics: Activities of Daily Living; Adult; Aged; Electromyography; Female; Humans; Male; Middle Aged; Muscle, Skeletal; Quadriceps Muscle; Time Factors; Young Adult
PubMed: 23349681
DOI: 10.1371/journal.pone.0052228 -
Cells, Tissues, Organs 2003Mammalian skeletal muscle fibers can be classified into functional types by the heavy chain (MyHC) and light chain (MyLC) isoforms of myosin (the primary motor protein)... (Comparative Study)
Comparative Study Review
Mammalian skeletal muscle fibers can be classified into functional types by the heavy chain (MyHC) and light chain (MyLC) isoforms of myosin (the primary motor protein) that they contain. Most human skeletal muscle contains fiber types and myosin isoforms I, IIA and IIX. Some highly specialized muscle fibers in human extraocular and jaw-closing muscles express either novel myosins or unusual combinations of isoforms of unknown functional significance. Extrinsic laryngeal muscles may express the extraocular MyHC isoform for rapid contraction and a tonic MyHC isoform for slow tonic contractions. In jaw-closing muscles, fiber phenotypes and myosin expression have been characterized as highly unusual. The jaw-closing muscles of most carnivores and primates have tissue-specific expression of the type IIM or 'type II masticatory' MyHC. Human jaw-closing muscles, however, do not contain IIM myosin. Rather, they express myosins typical of developing or cardiac muscle in addition to type I, IIA and IIX myosins, and many of their fibers are hybrids, expressing two or more isoforms. Fiber morphology is also unusual in that the type II fibers are mostly of smaller diameter than type I. By combining physiological and biochemical techniques it is possible to determine the maximum velocity of unloaded shortening (V(o)) of an individual skeletal muscle fiber and subsequently determine the type and amount of myosin isoform. When analyzed, some laryngeal fibers shorten at much faster rates than type II fibers from limb and abdominal muscle. Yet some type I fibers in masseter show an opposite trend towards speeds 10-fold slower than type I fibers of limb muscle. These unusual shortening velocities are most probably regulated by MyHC isoforms in laryngeal fibers and by MyLC isoforms in masseter. For the jaw-closing muscles, this finding represents the first case in human muscle of physiological regulation of kinetics by light chains. Together, these results demonstrate that, compared to other skeletal muscles, cranial muscles have a wider repertoire of contractile protein expression and function. Molecular techniques for reverse transcription of mRNA and amplification by polymerase chain reaction have been applied to typing of single fibers isolated from limb muscles, successfully identifying pure type I, IIA and IIX and hybrid type I/IIA and IIA/IIX fibers. This demonstrates the potential for future studies of the regulation of gene expression in jaw-closing and laryngeal muscles, which have such a variety of complex fiber types fitting them for their roles in vivo.
Topics: Animals; Humans; Laryngeal Muscles; Masseter Muscle; Rectus Abdominis
PubMed: 12784043
DOI: 10.1159/000070576 -
Biomaterials Apr 2013Ideal scaffolds that represent native extracellular matrix (ECM) properties of musculofascial tissues have great importance in musculofascial tissue engineering....
Ideal scaffolds that represent native extracellular matrix (ECM) properties of musculofascial tissues have great importance in musculofascial tissue engineering. However, detailed characterization of musculofascial tissues' ECM (particularly, of fascia) from large animals is still lacking. In this study, we developed a decellularization protocol for processing pig composite musculofascial tissues. Decellularized muscle (D-muscle) and decellularized fascia (D-fascia), which are two important components of decellularized musculofascial extracellular matrix (DMM), were comprehensively characterized. D-muscle and D-fascia retained intact three-dimensional architecture, strong mechanical properties, and bioactivity of compositions such as collagen, laminin, glycosaminoglycan, and vascular endothelial growth factor. D-muscle and D-fascia provided a compatible niche for human adipose-derived stem cell integration and proliferation. Heterotopic and orthotopic implantation of D-muscle and D-fascia in a rodent model further proved their biocompatibility and myogenic properties during the remodeling process. The differing characteristics of D-muscle from D-fascia (e.g. D-muscle's strong pro-angiogenic and pro-myogenic properties vs. D-fascia's strong mechanical properties) indicate different clinical application opportunities of D-muscle vs. D-fascia scaffolds. DMM comprising muscle and fascia ECM as a whole unit can thus provide not only a clinically translatable platform for musculofascial tissue repair and regeneration but also a useful standard for scaffold design in musculofascial tissue engineering.
Topics: Animals; Cell Proliferation; Collagen; DNA; Extracellular Matrix; Fascia; Glycosaminoglycans; Humans; Immunohistochemistry; Laminin; Male; Microscopy, Electron, Scanning; Muscles; Rats; Rats, Inbred F344; Regeneration; Swine; Tissue Engineering; Tissue Scaffolds; Vascular Endothelial Growth Factor A
PubMed: 23347834
DOI: 10.1016/j.biomaterials.2012.12.048