Mechanism of work-induced hypertrophy of skeletal muscle.
25/09/2013 · Is carbohydrate needed to further stimulate muscle protein synthesis/hypertrophy ..
The Ultimate Guide to Muscle Protein Synthesis
Now factors that promote protein synthesis such as IGF-1, growth hormone (GH), testosterone and some prostaglandins can commence the growth process. Protein synthesis occurs because a genetically-coded subtsance called 'messenger RNA' (mRNA) is sent out from the nucleus to the ribosomes. The nucleus is believed to release increased mRNA in response to tension and/or myofibrillar damage done as a result of insufficient cycling of actin-myosin cross-bridges during intense muscular contractions, though this mechanism is not fully understood. The mRNA contains the 'instructions' for the ribosomes to synthesize proteins, and so the process of constructing contractile (actin and myosin) and structural proteins (for the other components of the cell) from the amino acids taken into the cell from the bloodstream is set off. Several substances can influence this process. A short overview of the major ones are found below:
Increasing the volume of the tissue that supplies energy to the muscle or is involved with the neural drive: Intimately involved in the production of ATP are intracellular bodies called 'mitochondria'. Muscle fibers will adapt to high volume (and higher rep) training sessions by increasing the number of mitochondria in the cells. They will also increase the concentrations of the enzymes involved in the oxidative phosphorylation and anaerobic glycolysis mechanisms of energy production and increase the volume of sarcoplasmic fluid inside the cell (including glycogen) and also the fluid between the actual cells. This type of hypertrophy produces very little in the way of added limit strength but has profound effects on increasing strength-endurance (the ability to do reps with a certain weight) because it dramatically increases the muscles' ability to produce ATP. Adaptations of this sort are characteristic of Bodybuilders' muscles.
Protein timing and its effects on muscular hypertrophy …
As stated in Rennies 2004 review (26), it may take 20 weeks of resistance training to increase hypertrophy by 20%. This coincides very well with the research presented in this article, as it appears that the change in fiber size has a direct correlation to when satellite cells donate their nuclei for continued domain regulation. Therefore moderate increases in nuclear domain are very possible without the aided donation of nuclei from satellite cells and this does not appear to be rep range dependant. A statement can also be made that the results seen in small animals and humans may be very different. This may be owing to the extent of damage that is seen and how hypertrophy and necrotic damage stimulate the satellite pool differently but that is beyond the scope of this article.
There are two different types of muscular hypertrophy: sarcoplasmic and myofibrillar. During sarcoplasmic hypertrophy, the volume of in the muscle cell increases with no accompanying increase in muscular strength. During myofibrillar hypers, being the and contractile proteins, increase in number and add to muscular strength as well as a small increase in the size of the muscle. Sarcoplasmic hypertrophy is characteristic of the muscles of while myofibrillar hypertrophy is characteristic of .
Another study determined that muscle protein synthesis …
What can be seen when reviewing these and many other papers on the subject is the response to resistance training of fractional elevation remains in line with the results of feeding, both are elevated but the slower turnover proteins (myofibrillar) generally show a larger magnitude in increase. Since these studies show that this holds true with resistance training, dynamic exercise and HFES, all utilizing differing intensities and work output, it seems unlikely that the rep range is the sole cause of any increase in sarcoplasmic fraction up-regulation.
It was mentioned in the The Neuromuscular System Part I: What A Weight Trainer Needs To Know About Muscle article that muscle cells have many nuclei and other intracellular organelles. This is because nuclei are intimately involved in the protein synthesis process (don't forget, actin and myosin are proteins), and a single nuclei can only support the manufacturing of a limited amount of protein. If muscle cells didn't have multiple nuclei they would be very small muscle cells indeed. So if a muscle is to grow beyond its current size (i.e. synthesize contractile proteins - actin and myosin) it has to increase the number of nuclei that it contains (called the 'myonuclei number'). How does it do this?
by an increase in muscle protein synthesis.
Muscle protein synthesis is higher in oxidative fiber
Detailed description how muscle protein synthesis is measured and how to optimize it maximal muscle mass gains.
Resistance training and muscle protein synthesis
28/08/2015 · synthesis (MPS) and muscle protein breakdown (MPB), i.e. net muscle protein balance
does not increase muscle protein synthesis and hypertrophy
Insulin also promotes protein synthesis (hypertrophy or muscle growth) and prevents the breakdown of muscle
of net muscle protein synthesis) ..
Increasing the volume of contractile machinery: The vast majority of the volume of each muscle cell (~80%) is made up of contractile machinery. Therefore, therein lies the greatest potential for increasing muscle cell size. Trained muscle responds by increasing the number of actin/myosin filaments (sarcomeres) that it contains - this is, primarily, what is responsible for the increased strength and size. But before a muscle will grow like this it has to be 'broken down'. Let's take a look at both the 'breaking down' and 'building up' processes:
Protein synthesis occurs when the muscles ..
In a study looking at age affects of Protein Synthesis (6) it was noted that by the end of 2 weeks of weight-lifting exercise, MHC and mixed protein synthesis rates increased in both younger and older participants. The actin protein synthesis rate was increased after exercise in only the younger group. The magnitude of the exercise-induced increase in MHC and mixed protein synthesis rates was similar in the younger and older groups. In the younger group, the MHC and Actin (contractile) protein synthesis rate increased 83% and 78% respectively while the mixed muscle protein synthesis rate increased (102%). This study points to the identification that, as with feeding, all proteins are up regulated with resistance exercise. Now the interesting point was that the exercise protocol used seven weight-lifting exercises (Nautilus equipment) that included the chest press, inclined chest press, latissimus pull-down (wide and narrow grip), leg press, knee extension, knee flexion, and two free weight-lifting exercises that included seated overhead press and overhead triceps extension. Each participant completed ten weight-lifting exercise sessions: 23 sets/day of the nine exercises listed above, 812 repetitions/set, 6090% of maximum voluntary muscle strength. This was a pretty broad range of intensity and easily points out that the rep range itself isnt the determining factor.
How Does Muscle Hypertrophy Happen? - Verywell
In addition, there are other intracellular bodies whose growth and/or proliferation would fall under the category of sarcoplasmic hypertrophy. These would be organelles such as the ribosomes, which are involved in protein synthesis. As in the case of neural drive machinery, in most cases they would increase in size or number only to support sarcomere hypertrophy. They would have little impact on overall muscle size.
You Don't Need Large Amounts Of Protein To Build Muscle
Atherton et al. (7) used electrical stimulation with high frequency (HFS; 6x10 repetitions of 3 s-bursts at 100 Hz to mimic resistance training) to identify signalling present during increased protein synthesis. What he noted, significant to this article and discussion, was that HFS significantly increased myofibrillar and sarcoplasmic protein synthesis 3 h after stimulation 5.3 and 2.7 fold, respectively.
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