To understand protein synthesis, it's important to become better acquainted with mTor. Research tells us that when you force a muscle to contract against a heavy load, the primary response is an activation of protein synthesis. Protein synthesis activation is, in turn, controlled by a series of phosphorylation events orchestrated by a protein called mammalian target of rapamycin, or mTOR for short.
mTOR is arguably the most important cell signaling complex for muscle growth. It's the master-controller of protein synthesis in the cell, and there's a direct relationship between muscle growth and mTOR activation; the more a workout activates mTOR, the more the protein synthesis machinery cranks out new proteins for muscle growth and repair.
Neurobiological substrates supporting human social cognition and behavior. Review and synthesis of relevant research in neuropsychology, psychiatry, neuroimaging and experimental animal research.
More recent studies looking at a more general model for protein synthesis show that insulin + amino acids can have a synergistically positive effect on protein synthesis, causing the greatest mTOR activation together!
This originally came as quite a surprise, because insulin is a potent activator of protein synthesis. Insulin activates mTOR by way of PI3K/akt signaling, which is parallel to the pathways used by amino acids and mechanical stress to activate mTOR.
But add in an intense training session with the right nutrient intake at the right time and things change; protein synthesis is activated and degradation is suppressed. The result is an accumulation of muscle protein over time, as shown in the figure below.
During training, ATP is burned to fuel muscle contractions, which increases AMP levels. This activates a protein called AMP kinase (AMPK). AMPK reduces protein synthesis by inhibiting mTOR.
Importantly, this reservoir of peroxidase-processed thyroglobulin is usually enough for months of use explaining why defects in thyroid hormone synthesis often take months to become clinically apparent.
Importantly, activation of protein synthesis in the seems to ultimately determine how well we respond to training in the . What this means is that not only are workouts needed to maximally activate protein synthesis, but the right nutrition needs to be there at precisely the right time for this to happen.
There's been considerable research on exactly what type of nutrition is needed to maximally activate protein synthesis. While we'll discuss specifics later, it's important to know that only the essential amino acids (EAAs) have been shown to activate protein synthesis, with in particular being the most important for turning on the protein synthesis machinery.
It's also clear from the literature that carbs aren't needed to activate protein synthesis after training, but there are other reasons to include carbs, which we'll get into later.
It's important to realize that the kind of intense, balls-out training most T NATION readers do probably activates protein synthesis to a greater degree than what researchers are using in the lab. Therefore, .
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