Figure - available from: Frontiers in Physiology
This content is subject to copyright.
Conceptualization of conventional versus sarcoplasmic hypertrophy, and how these phenomena would manifest with the electrophoresis technique discussed. The left inset demonstrates various modes of muscle fiber hypertrophy. The small blue circles within the fiber represent mitochondria, the smaller gray circles occupying most of the intracellular space represent myofibrils, and the remainder of the space represents the sarcoplasm. In situations where hypertrophy occurs due to the proportional accretion of myofibrillar protein (i.e., conventional hypertrophy), there could either be the addition of new myofibrils to the periphery which “push” the cell outward (indicated as new yellow dots), or there could be the thickening of pre-existing myofibrils (indicated by the haloing of gray circles). Alternatively, sarcoplasmic hypertrophy occurs through the disproportionate expansion of the sarcoplasm relative to myofibril addition. Select studies have shown this process may occur in response to resistance training, although some studies refute this model of hypertrophy. This process could potentially be shown through TEM imaging, phalloidin staining, or the determination of specific tension in isolated fibers (not depicted in figure). This process could also be reflected when analyzing pre- and post-training biopsy specimens through SDS-PAGE and Coomassie staining, and analyzing the changes in myosin heavy chain (MHC) and actin protein band densities (illustrated on the right inset of the figure).
Source publication
Skeletal muscle fibers are multinucleated cells that contain mostly myofibrils suspended in an aqueous media termed the sarcoplasm. Select evidence suggests sarcoplasmic hypertrophy, or a disproportionate expansion of the sarcoplasm relative to myofibril protein accretion, coincides with muscle fiber or tissue growth during resistance training. The...
Similar publications
Introduction :La frequence des malformations uterines est estimee entre 0,5 et 4 %. Ces anomalies peuvent avoir des repercussions sur levolution de la conception. Patients et observation :Nous rapportons trois cas de RCIU associee a un oligoamniossecondaire a des malformations uterines decouvertes en per operatoire type : uterus pseudo unicorne dan...
The article is devoted to solving the problem of the development of startup ecosystems in
the countries of Central and Eastern Europe (including Ukrainian entrepreneurship since Ukraine
gained independence) by reorienting their economy to a market economy and conducting it based on
sustainable development, ethics, and social responsibility. It has...
Las anomalías congénitas Mullerianas son las que afectan al desarrollo y la morfología de las trompas de Falopio, del útero y/o de la vagina, con o sin anomalías asociadas de ovario, del tracto urinario, esqueléticas o de otros órganos. El desarrollo normal del tracto reproductivo femenino implica una serie de procesos complejos caracterizados por...
In April 2017, a double teratological case in an adult Monachoides incarnatus
(Müller, 1774) was discovered in Liège (Belgium). The specimen constitutes a “unicorn snail”, where the snail owns only one central ommatophore (eye-stalk) with two eyes at the top of the tentacle, and a supernumerary small eye close to the right eye. The unique upper sta...
Citations
... Some have hypothesized that the disconnect between changes in muscle size and strength may be due to sarcoplasmic (i.e. disproportionately larger increase in non-force generating elements) rather than myofibrillar hypertrophy (Roberts et al., 2020). If that thesis is true, it could potentially explain the disconnect between muscle growth and changes in strength following low load training with blood flow restriction and high-load training. ...
... This would facilitate the estimations on how many sets are sufficient if a high metabolic load is to be achieved with increasing load. For example, metabolic perturbations are important factors for sarcoplasmic hypertrophy, which is associated with muscle fiber growth during resistance training [25]. In this context, on a cellular level several sarcoplasmic proteins such as Creatine kinase M-type, Beta-enolase and Pyruvate kinase are upregulated after strength exercise, which indicates an increased activation of the glycolytic metabolism [12]. ...
Inertia-based resistance exercise with flywheels leads to strong acute metabolic responses. However, the metabolic kinetics during a multi-set flywheel squat protocol with increasing loads remains unknown. The aim of the study was to assess the course of blood lactate concentrations (BLC), oxygen uptake (VO 2 ), heart rate (HR) and power during a multi-set protocol of flywheel squat training. Seventeen recreationally trained healthy men (24.3 ± 3.8 years, BMI 24.1 ± 2.2, VO 2max 49.4 ± 6.9 mL/min/kg) completed 5 sets and 15 repetitions flywheel squats. The BLC ( ŋ ² = 0.932), VO 2 ( ŋ ² = 0.899) and HR ( ŋ ² = 0.879) increased significantly over the sets ( P < 0.05). %HR max and %VO 2max increased significantly from pre to post-loading ( P < 0.001), reaching a threshold of 80% HR max after set 2 and 60% VO 2max after set 4, respectively. The power parameters P MEAN ( ŋ ² = 0.191), P ECC ( ŋ ² = 0.149) and P CON ( ŋ ² = 0.062) showed significant decreases after set 2 ( P < 0.05). A multi-set flywheel squat protocol with increasing loads leads to high metabolic and cardiorespiratory demands, which appear to increase linearly with an increase in inertial load.
... Beyond the classic hypertrophy observed in the contractile elements (e.g., myofibers), other noncontractile sarcoplasmic proteins may accumulate within skeletal muscle fibers. Sarcoplasmic hypertrophy has been discussed previously as an adaptation to RET that may or may not be possible (11,202). Although some suggest that high-volume training may promote sarcoplasmic hypertrophy to a greater extent than high-load training (202), relatively few studies have examined sarcoplasmic hypertrophy in this context. ...
... Sarcoplasmic hypertrophy has been discussed previously as an adaptation to RET that may or may not be possible (11,202). Although some suggest that high-volume training may promote sarcoplasmic hypertrophy to a greater extent than high-load training (202), relatively few studies have examined sarcoplasmic hypertrophy in this context. ...
High-load resistance exercise (>60% of 1-repetition maximum) is a well-known stimulus to enhance skeletal muscle hypertrophy with chronic training. However, studies have intriguingly shown that low-load resistance exercise training (RET) (≤60% of 1-repetition maximum) can lead to similar increases in skeletal muscle hypertrophy as compared to high-load RET. This has raised questions about the underlying mechanisms for eliciting the hypertrophic response with low-load RET. A key characteristic of low-load RET is performing resistance exercise to, or close to, task failure, thereby inducing muscle fatigue. The primary aim of this evidence-based narrative review is to explore whether muscle fatigue may act as an indirect or direct mechanism contributing to skeletal muscle hypertrophy during low-load RET. It has been proposed that muscle fatigue could indirectly stimulate muscle hypertrophy through increased muscle fibre recruitment, mechanical tension, ultrastructural muscle damage, the secretion of anabolic hormones, and/or alterations in the expression of specific proteins involved in muscle mass regulation (e.g., myostatin). Alternatively, it has been proposed that fatigue could directly stimulate muscle hypertrophy through the accumulation of metabolic by-products (e.g., lactate), and/or inflammation and oxidative stress. This review summarizes the existing literature eluding to the role of muscle fatigue as a stimulus for low-load RET-induced muscle hypertrophy and provides suggested avenues for future research to elucidate how muscle fatigue could mediate skeletal muscle hypertrophy.
... A hipertrofia muscular tem sido amplamente estudada em humanos e modelos animais, sendo induzida por métodos como tenotomia ou ablação de músculos sinérgicos. Essa hipertrofia pode ser avaliada em nível macroscópico através de técnicas de imagem como DXA, TC, MRI e ultrassonografia, e em nível microscópico pela área de secção transversal (CSA) das fibras musculares (Roberts et al., 2020). Romero et al. (2013) discutem os principais hormônios e fatores de crescimento que influenciam a massa muscular e promovem a hipertrofia do músculo esquelético. ...
Este estudo teve como objetivo avaliar os efeitos do BCAA injetável na síntese de proteínas musculares e na composição corporal, investigando seu papel no aumento de massa muscular e na recuperação pós-exercício. A metodologia consistiu em uma revisão bibliográfica abrangente em bases de dados como PubMed, SciELO e Google Scholar, focando em estudos de eficácia e segurança. Os principais resultados sugerem que, apesar de o BCAA injetável promover um aumento temporário na síntese proteica, os benefícios são limitados quando comparados à ingestão de proteínas completas, que fornecem todos os aminoácidos essenciais. Além disso, o estudo destaca que o uso contínuo de BCAA injetável pode causar sobrecarga renal, especialmente em pessoas predispostas a problemas renais, além de apresentar riscos como hipoglicemia e resistência à insulina. A conclusão reforça que o BCAA injetável, embora auxilie na recuperação muscular e potencialize a oxidação de ácidos graxos, deve ser utilizado com cautela e em combinação com uma alimentação adequada para garantir resultados seguros e eficazes.
... Previously it has been shown that supplementation of insulin stimulates hypertrophy of mature single myo bres in vitro, while the increase in maximal force remains half of the percentage of increase in CSA when the number of sarcomeres in series is unchanged 50 . It is conceivable that the production of contractile machinery and functional improvement is delayed compared to the increase in muscle mass 51 . This observation is in line with the concurrently reduced speci c force and myosin content in myostatin-null mice, indicating a reduced number of functional bound cross-bridges 30 . ...
Transforming growth factor-β (TGF-β) signaling is associated with progressive skeletal muscle wasting and fibrosis, while double knockout of TGF-β type I receptors Acvr1b and Tgfbr1 results in hypertrophy. Gaining insights in how myofibre-specific knockout of these receptors affects muscle transcriptome, strength and mitochondrial activity could aid in the development of therapeutic interventions to improve muscle function. Here, we show that 3 months of myofibre-specific knockout of both receptors (dKO) in mice induced a 1.6-fold increase in gastrocnemius medialis mass and a 1.3-fold increase in maximal force. Soleus muscle mass and maximal force both increased 1.2-fold in dKO mice. Muscle hypertrophy in dKO mice was accompanied by a proportional increase in succinate dehydrogenase enzyme activity. Single receptor knockout caused minor phenotypical alterations. Transcriptome analyses revealed that gastrocnemius medialis had 1811 and soleus had 295 differentially expressed genes, mainly related to muscle contraction, hypertrophy, filament organization and oxidative metabolism. Hgf and Sln genes were strongly upregulated in both muscles of dKO mice, while Sntb1 was downregulated. This in combination of transcriptional changes are associated with muscle hypertrophy and increased mitochondrial biosynthesis. Our study highlights that myofibre-specific interference with both TGF-β type I receptors concurrently stimulates myofibre hypertrophy and mitochondrial activity.
... Given the composition of skeletal muscle, patients in Cluster 2 probably developed a different kind of hypertrophy, not only caused by an increase in sarcomeres or myofibrils but also by connective tissue hypertrophy (due to an increase in the volume of the extracellular matrix that shows an increase in mineral or protein) [21]. ...
Our study investigates the post-mortem findings of the diaphragm's muscular structural changes in mechanically ventilated COVID-19 patients. Diaphragm samples of the right side from 42 COVID-19 critically ill patients were analyzed and correlated with the type and length of mechanical ventilation (MV), ventilatory parameters, prone positioning, and use of sedative drugs. The mean number of fibers was 550±626. The cross-sectional area was 4120±3280 μm 2 , while the muscular fraction was 0.607±0.126. The overall population was clustered into two distinct populations (clusters 1 and 2). Cluster 1 showed a lower percentage of slow myosin fiber and higher fast fiber content than cluster 2, 68% versus 82%, p<0.00001, and 29.8% versus 18.8%, p=0.00045
... For instance, a plethora of studies have shown that an increase in mechanical loading, such as that which occurs during resistance exercise (RE), can induce radial growth of the muscle fibers (Conceição et al., 2018;Ema et al., 2016;Williams and Goldspink, 1971;Haun et al., 2019;Jorgenson et al., 2020). Surprisingly, however, the ultrastructural adaptations that drive this response have not been well defined (Haun et al., 2019;Jorgenson et al., 2020;Roberts et al., 2020). Indeed, a number of seemingly simple and fundamental important questions have not been answered. ...
... myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) has not been resolved (Jorgenson et al., 2020;Roberts et al., 2020;Wang et al., 1993;Ashmore and Summers, 1981). ...
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e. an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e. myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (fluorescence imaging of myofibrils with image deconvolution [FIM-ID]). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
... For instance, a plethora of studies have shown that an increase in mechanical loading, such as that which occurs during resistance exercise (RE), can induce radial growth of the muscle fibers (Conceição et al., 2018;Ema et al., 2016;Williams and Goldspink, 1971;Haun et al., 2019;Jorgenson et al., 2020). Surprisingly, however, the ultrastructural adaptations that drive this response have not been well defined (Haun et al., 2019;Jorgenson et al., 2020;Roberts et al., 2020). Indeed, a number of seemingly simple and fundamental important questions have not been answered. ...
... myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) has not been resolved (Jorgenson et al., 2020;Roberts et al., 2020;Wang et al., 1993;Ashmore and Summers, 1981). ...
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e., an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e., myofibril hypertrophy) and/or the number of myofibrils (i.e., myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (FIM-ID). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a fundamentally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
... For instance, a plethora of studies have shown that an increase in mechanical loading, such as that which occurs during resistance exercise (RE), can induce radial growth of the muscle fibers (Conceição et al., 2018;Ema et al., 2016;Williams and Goldspink, 1971;Haun et al., 2019;Jorgenson et al., 2020). Surprisingly, however, the ultrastructural adaptations that drive this response have not been well defined (Haun et al., 2019;Jorgenson et al., 2020;Roberts et al., 2020). Indeed, a number of seemingly simple and fundamental important questions have not been answered. ...
... myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) has not been resolved (Jorgenson et al., 2020;Roberts et al., 2020;Wang et al., 1993;Ashmore and Summers, 1981). ...
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e., an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e., myofibril hypertrophy) and/or the number of myofibrils (i.e., myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (FIM-ID). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a foundationally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
... For instance, a plethora of studies have shown that an increase in mechanical loading, such as that which occurs during resistance exercise (RE), can induce radial growth of the muscle fibers (Conceição et al., 2018;Ema et al., 2016;Williams and Goldspink, 1971;Haun et al., 2019;Jorgenson et al., 2020). Surprisingly, however, the ultrastructural adaptations that drive this response have not been well defined (Haun et al., 2019;Jorgenson et al., 2020;Roberts et al., 2020). Indeed, a number of seemingly simple and fundamental important questions have not been answered. ...
... myofibril hypertrophy) and/or the number of myofibrils (i.e. myofibrillogenesis) has not been resolved (Jorgenson et al., 2020;Roberts et al., 2020;Wang et al., 1993;Ashmore and Summers, 1981). ...
An increase in mechanical loading, such as that which occurs during resistance exercise, induces radial growth of muscle fibers (i.e., an increase in cross-sectional area). Muscle fibers are largely composed of myofibrils, but whether radial growth is mediated by an increase in the size of the myofibrils (i.e., myofibril hypertrophy) and/or the number of myofibrils (i.e., myofibrillogenesis) is not known. Electron microscopy (EM) can provide images with the level of resolution that is needed to address this question, but the acquisition and subsequent analysis of EM images is a time- and cost-intensive process. To overcome this, we developed a novel method for visualizing myofibrils with a standard fluorescence microscope (FIM-ID). Images from FIM-ID have a high degree of resolution and contrast, and these properties enabled us to develop pipelines for automated measurements of myofibril size and number. After extensively validating the automated measurements, we used both mouse and human models of increased mechanical loading to discover that the radial growth of muscle fibers is largely mediated by myofibrillogenesis. Collectively, the outcomes of this study offer insight into a foundationally important topic in the field of muscle growth and provide future investigators with a time- and cost-effective means to study it.
