Etudes Musculation

Rôle des vésicules extracellulaires dans la croissance

29/06/2019 | Etudes sur les hormones et Etudes Musculation


Emerging role of extracellular vesicles in the regulation of skeletal muscle adaptation
Ivan J. Jr Vechetti           j appl physiol 13 juin 2019

Extracellular vesicles (EVs) were initially characterized as “garbage” bags with the finality to remove unwanted material from the cells. It is now becoming clear that EVs mediate intercellular communication between distant cells through a transfer of genetic material, a process important to the systemic adaptation in physiological and pathological conditions.

Although speculative, it has been suggested that the majority of EVs that make it into the bloodstream would be coming from skeletal muscle, since it is one of the largest organs in the human body. While it is well established that skeletal muscle secretes peptides (currently known as myokines) into the bloodstream, the notion that skeletal muscle releases EVs is in its infancy. Besides intercellular communication and systemic adaptation, EV release could represent the mechanism by which muscle adapts to certain stimuli. This review will summarize the current understanding of EV biology and biogenesis, current isolation methods, and briefly discuss the possible role EVs have in regulating skeletal muscle mass.

Comment la souplesse thoracique augmente-t’elle?

26/05/2019 | Musculation des pectoraux et Etudes Musculation


Effect of intercostal muscle contraction on rib motion in humans studied by finite element analysis
Guangzhi Zhang   japplphysiol.00995.2017

The effect of intercostal muscle contraction on generating rib motion has been investigated for a long time and is still controversial in physiology. This may be because of the complicated structure of the rib cage, making direct prediction of the relationship between intercostal muscle force and rib movement impossible. Finite element analysis is a useful tool that is good at solving complex structural mechanic problems.

In this study, we individually activated the intercostal muscle groups from the dorsal to ventral portions and obtained five different rib motions classified based on rib moving directions. We found that the ribs cannot only rigidly rotate around the spinal joint but also be deformed, particularly around the relatively soft costal cartilages, where the moment of muscle force for the rigid rotation is small. Although the intercostal muscles near the costal cartilages cannot generate a large moment to rotate the ribs, the muscles may still have a potential to deform the costal cartilages and contribute to the expansion and contraction of the rib cage based on the force-length relationship.

Our results also indicated that this potential is matched well with the special shape of the costal cartilages, which become progressively oblique in the caudal direction. Compared with the traditional explanation of rib motion, by additionally considering the effect from the tissue deformation, we found that the special structure of the ventral portion of the human rib cage could be of mechanical benefit to the intercostal muscles, generating inspiratory and expiratory rib motions.

NEW & NOTEWORTHY Compared with the traditional explanation of rib motion, additionally considering the effect from tissue deformation helps us understand the special structure of the ventral portion of the human rib cage, such that the costal cartilages progressively become oblique and the costochondral junction angles gradually change into nearly right angles from the upper to lower ribs, which could be of mechanical benefit to the intercostal muscles in the ventral portion, generating inspiratory and expiratory rib motions.

Comment la brûle déclenche l’anabolisme?

09/05/2019 | Etudes sur les hormones et Etudes Musculation et Etudes Compléments alimentaires


IL-6 release from muscles during exercise is stimulated by lactate-dependent protease activity
Pernille Hojman       08 MAY 2019 ajpendo

IL-6 is secreted from muscles to the circulation during high-intensity and long-duration exercise, where muscle-derived IL-6 works as an energy sensor to increase release of energy substrates from liver and adipose tissues. We investigated the mechanism involved in the exercise-mediated surge in IL-6 during exercise. Using interval-based cycling in healthy young men, swimming exercise in mice, and electrical stimulation of primary human muscle cells, we explored the role of lactate production in muscular IL-6 release during exercise. First, we observed a tight correlation between lactate production and IL-6 release during both strenuous bicycling and electrically stimulated muscle cell cultures. In mice, intramuscular injection of lactate mimicked the exercise-dependent release of IL-6, and pH buffering of lactate production during exercise attenuated IL-6 secretion. Next, we used in vivo bioimaging to demonstrate that intrinsic intramuscular proteases were activated in mice during swimming, and that blockade of protease activity blunted swimming-induced IL-6 release in mice. Last, intramuscular injection of the protease hyaluronidase resulted in dramatic increases in serum IL-6 in mice, and immunohistochemical analyses showed that intramuscular lactate and hyaluronidase injections led to release of IL-6-containing intramyocellular vesicles. We identified a pool of IL-6 located within vesicles of skeletal muscle fibers, which could be readily secreted upon protease activity. This protease-dependent release of IL-6 was initiated by lactate production, linking training intensity and lactate production to IL-6 release during strenuous exercise.

Régulation des ribosomes dans l’hypertrophie?

22/03/2019 | Etudes Musculation


Regulation of Ribosome Biogenesis During Skeletal Muscle Hypertrophy
Kim, Hyo-Gun         Exercise and Sport Sciences Reviews: April 2019 - Volume 47 - Issue 2 - p 91–97

An increase in ribosomal capacity is a hallmark of the hypertrophying muscle. We review evidence demonstrating that transcription of ribosomal RNA genes is necessary for the increase in ribosomal capacity, and this is critical for muscle growth in human and animal models of hypertrophy.

Hyperplasie musculaire pour la croissance?

22/03/2019 | Etudes Musculation


Muscle Fiber Splitting Is a Physiological Response to Extreme Loading in Animals
Murach, Kevin A           Exercise and Sport Sciences Reviews: April 2019 - Volume 47 - Issue 2 - p 108–115

Skeletal muscle fiber branching and splitting typically is associated with damage and regeneration and is considered pathological when observed during loading-induced hypertrophy. We hypothesize that fiber splitting is a nonpathological component of extreme loading and hypertrophy, which is primarily supported by evidence in animals, and propose that the mechanisms and consequences of fiber splitting deserve further exploration.

Comment expliquer la mémoire musculaire (suite)?

17/02/2019 | Etudes Musculation


Comparative Transcriptome and Methylome Analysis in Human Skeletal Muscle Anabolism, Hypertrophy and Epigenetic Memory.
Daniel C Turner         bioRxiv posted 15 February 2019

Transcriptome wide changes in human skeletal muscle after acute (anabolic) and chronic resistance exercise (RE) induced hypertrophy have been extensively determined in the literature. We have also recently undertaken DNA methylome analysis (850,000 + CpG sites) in human skeletal muscle after acute and chronic RE, detraining and retraining, where we identified a role for DNA methylation in an epigenetic memory of exercise induced skeletal muscle hypertrophy. However, it is currently unknown as to whether all the genes identified in the transcriptome studies to date are also epigenetically regulated at the DNA level after acute, chronic or repeated RE exposure. We therefore aimed to undertake large scale bioinformatical analysis by pooling the publicly available transcriptome data after acute (110 samples) and chronic RE (181 samples) and comparing these large data sets with our genome-wide DNA methylation analysis in human skeletal muscle after acute and chronic RE, detraining and retraining. Indeed, after acute RE we identified 866 up- and 936 down-regulated genes at the expression level, with 270 (out of the 866 up-regulated) identified as being hypomethylated, and 216 (out of 936 downregulated) as hypermethylated. After chronic RE we identified 2,018 up- and 430 down-regulated genes with 592 (out of 2,018 upregulated) identified as being hypomethylated and 98 (out of 430 genes downregulated) as hypermethylated. After KEGG pathway analysis, genes associated with cancer pathways were significantly enriched in both bioinformatic analysis of the pooled transcriptome and methylome data after both acute and chronic RE. This resulted in 23 (out of 69) and 28 (out of 49) upregulated and hypomethylated and 12 (out of 37) and 2 (out of 4) downregulated and hypermethylated cancer genes following acute and chronic RE respectively. Within skeletal muscle tissue, these cancer genes predominant functions were associated with matrix/ actin structure and remodelling, mechano-transduction (including PTK2/Focal Adhesion Kinase and Phospholipase D- following chronic RE only), TGF-beta signalling and protein synthesis (GSK3B after acute RE only). Interestingly, 51 genes were also identified to be up/downregulated in both the acute and chronic RE pooled transcriptome analysis as well as significantly hypo/hypermethylated after acute RE, chronic RE, detraining and retraining.

Five genes; FLNB, MYH9, SRGAP1, SRGN, ZMIZ1 demonstrated increased gene expression in the acute and chronic RE transcriptome and also demonstrated hypomethylation in these conditions. Importantly, these 5 genes demonstrated retained hypomethylation even during detraining (following training induced hypertrophy) when exercise was ceased and lean mass returned to baseline (pre-training) levels, identifying them as novel epigenetic memory genes. Importantly, for the first time across the transcriptome and epigenome combined, this study identifies novel differentially methylated genes associated with human skeletal muscle anabolism, hypertrophy and epigenetic memory.

Peut-on perdre du muscle en gardant sa force au régime?

28/11/2018 | Etudes Musculation et Etudes Perte de poids


Si tu veux clacher tous les coachs à la mode

A Low-Carbohydrate Ketogenic Diet Reduces Body Mass Without Compromising Performance in Powerlifting and Olympic Weightlifting Athletes
Greene, David A       The Journal of Strength & Conditioning Research: December 2018 - Volume 32 - Issue 12 - p 3373–3382

There is evidence that low carbohydrate diets might offer specific advantages for weight reduction without the negative impact on strength and power previously hypothesized to accompany carbohydrate restriction. Therefore, the purpose of this study was to determine whether a low-carbohydrate ketogenic diet (LCKD) could be used as a weight reduction strategy for athletes competing in the weight class sports of powerlifting and Olympic weightlifting.

Fourteen intermediate to elite competitive lifting athletes (age 34 ± 10.5, n = 5 female) consumed an ad libitum usual diet (UD) (>250 g daily intake of carbohydrates) and an ad libitum LCKD (≤50 g or ≤10% daily intake of carbohydrates) in random order, each for 3 months in a crossover design. Lifting performance, body composition, resting metabolic rate, blood glucose, and blood electrolytes were measured at baseline, 3 months, and 6 months.

The LCKD phase resulted in significantly lower body mass (−3.26 kg, p = 0.038) and lean mass (−2.26 kg, p = 0.016) compared with the UD phase.

Lean mass losses were not reflected in lifting performances that were not different between dietary phases.

No other differences in primary or secondary outcome measures were found between dietary phases. Weight class athletes consuming an ad libitum LCKD decreased body mass and achieved lifting performances that were comparable with their UD. Coaches and athletes should consider using an LCKD to achieve targeted weight reduction goals for weight class sports.

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