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= mTOR, Muscular Growth, and Longevity = mTOR is the Mammalian Target of Rapamycin. It is composed of two mechanisms, namely mTOR Complex 1 and 2 (mTORC1 and mTORC2 respectively). mTORC1 is nutrient sensitive whereas mTORC2 has more to do with survival. mTOR is essentially a regulator of all processes in the human body so it is naturally a part of the conversation when it comes to human longevity. Years of science has backed the fact that consideration put into one’s dietary, exercise, and other lifestyle choices can improve one’s longevity. Recently, studies done on mTOR show that it is a critical vector affected by said choices and consequently provides a direct effect on an individual’s longevity. (Mota-Martorell, 2020)

General Background

Define Muscular growth and give some background
Muscular growth refers to the increase in muscle mass. It can be achieved via two mechanisms: muscular hypertrophy, and muscular hyperplasia. Hypertrophy, in this context, refers to the increase in muscular size due to the enlargement of muscle fibers in response to some stimulus. Muscular hyperplasia refers to the increased number of cells acquired through strength training. Muscular hypertrophy is typically the primary mechanism for muscular growth. Strength training paired with adequate protein intake results in increased muscle accrual.

Protein consumption causes increases in mTOR signaling activation and makes way for muscle protein synthesis. Muscle protein synthesis, for example, leverages mTOR activation be cause mTORC1 is activated by the amino acids that come from the digestion of the protein ingested by the individual. By leveraging this pathway, mTOR signaling due to protein intake and the consequent contractile tissue accrual makes it so that osteoporosis (when leveraging strength training to better utilize protein ingestion and its effects on muscle mass accrual) and muscle wasting in general is staved off. This positively impacts longevity.

Muscle Protein Synthesis for Longevity
While protein ingestion induces mRNA translation through mTORC1 to promote cell growth and benefit longevity (the necessary development for healthy well-being is supported)., protein ingestion can work in tandem with resistance training to maximize longevity. (Song, 2017) Muscle protein synthesis relies in part on external stimuli, say, presented via resistance training. Sure, amino acid presence can result in nutrient sensitive mTORC1 to start mTOR signaling activation. However, mTORC1 also responds to resistance training. (Song, 2017) Adequate muscle protein synthesis relies on mTOR to spike in response to the presence of amino acids and resistance training. If an individual has an adequate protein intake and pairs said protein intake with resistance training, muscular hypertrophy and hyperplasia can be initiated. Having accrued more active tissue than before, and individual can rely on the increased energy expenditure to lose body fat, improve insulin sensitivity, and be better prepared for functional movement well into senescence. All of these outcomes increase the likelihood that longevity is maximized.

Considering Different Training Methodologies
When considering muscular hypertrophy, it is understood that the most important thing to consider is total volume across various exercises focusing on any particular group of muscles/individual muscles. (NEED STUDY) What would be interesting to consider is the impact of various training methodologies on mTOR signaling activation and the resultant impact on muscular hypertrophy. Resistance training does play a role in activating mTOR (specifically mTORC1) at a base level. (SOURCE)

High volume training impact on mTOR
Higher volume training would, in a general sense, introduce more opportunities for resistance training induced mTOR spikes. Then, the cascade into mTORC1 starting cell growths would cause the impacts on longevity discussed in the other assignment (literature review, also NEED SOURCE).

HIIT training impact on mTOR:
https://journals.physiology.org/doi/full/10.1152/ajpregu.00479.2015

Concurrent training impact on mTOR:

https://physoc.onlinelibrary.wiley.com/doi/full/10.14814/phy2.14411

Androgens, Associated Resceptors, and the Hormonal Component Interactions with mTOR:
The role of androgen receptor in muscular hypertrophy in response to mTOR pathway being activated through resistance training:

https://link.springer.com/article/10.1186/s12986-020-00446-y ;

Androgen receptor density varies within muscle groups.

Macronutrient Role in mTOR and Muscular Hypertrophy
mTORC1 activation is observed red as mTORC1 is understood to be nutrient-sensitive. Since mTOR is a growth regulator, mTOR signaling in presence of amino acids (monomers of the protein macronutrient) especially, paired with micro-damage in existing musculature, will support the process of muscle protein synthesis and lead to the accrual of active tissue over time. This is the role protein plays play in muscular hypertrophy.

Glucose is a monomer of the carbohydrate macronutrient. Glucose also plays an impact on muscular hypertrophy. The presence of glucose in large amounts can inhibit the sig

https://www.nature.com/articles/s41598-020-65397-z

Nutrient intake and the resultant cell growth regulation happens through mTORC1.

Protein:
The primary macronutrient required for mTORC1 to begin muscle protein synthesis is protein.