During my competitive bodybuilding years I, just like everyone else in this particular field, was mainly interested in increasing my muscle size. This is no longer the case. Still, the science of inducing Muscle Protein Synthesis (MPS) and counteracting the Muscle Protein Breakdown (MPB) fascinates me a lot. It still applies to what I do, if not for any other reason, at least for the fact that being careless in this matter might result in losing muscle mass – and from there diminishing athletic performance. And, I care a lot about optimal athletic performance.
While I was researching my post on the methods for calculating protein intake, I stumbled on a meta study. In this post I want to examine this meta study alone. It’s quite interesting and, even more importantly, it is written in a language that a layman like me can easily understand. I encourage you to read the paper if you have time.
The name of the paper is, “A Brief Review of Critical Processes in Exercise-Induced Muscular Hypertrophy” and it could be found here. Of course, the paper includes references to other papers, based on which it draws its conclusions (in case you’re interested in the sources).
My notes are below. I’ve capitalized a few words here and there for additional emphasis. I did this only in places where the conclusion drawn ran counter-intuitive to popular belief (and counter-intuitive to many industry publications and the advertisers in them), or I didn’t know about it at all.
Regulation of muscle protein turnover
- Resistance exercise in a fed state (with enough protein) promotes Muscle Protein Synthesis (MPS)
- Resistance exercise in a fasted state promotes Muscle Protein Breakdown (MPB)
- Addition of amino acids post-exercise suppresses the rise in MPB
- Post-exercise (PE) hyperinsulinemia (from fast-digesting carbs with your PE protein) does not cause MPS, but it suppresses MPB
- ONLY the essential amino acids (EAA) produce MPS
- The EAA Leucine ALONE appears to be the metabolic trigger for MPS
- Exercise increases the sensitivity to Leucine. Aging and inactivity decrease it
- Post-exercise is the most optimal period for inducing aminoadicemia (eating protein) which in turn induces MPS
- Protein synthesis in the muscles remains enhanced for at least 24 hours PE.
Protein dose and MPS response
- Young people (in their 20-ies) achieve the same MPS with just 20g protein (0.25g/kg body mass/meal) PE that old adults (in their 70-ies) can achieve with close to 40g of protein
- Beyond these levels of protein intake the amino acids are more heavily oxidized (not entirely used for MPS)
Protein quality and muscle protein turnover
- Even a protein dose that is 25 percent of what is considered to be an optimal dose for MPS can become ‘optimal’ with the addition of the amino acid Leucine.
- Whey is superior to casein in stimulating MPS despite the fact that it is only 20 percent higher in Leucine. This effect of superiority is due to the fact that whey is digested much faster than casein
- Proteins with naturally higher Leucine content (whey) are superior for inducing MPS when compared to proteins with naturally lower Leucine content (soy).
Protein and weight loss
- High-quality protein in doses that are higher than the normally consumed (15-17 percent of calories is what’s normally consumed) has a ‘sparing’ effect on muscle tissue only when the calorie deficit is not huge. The higher the calorie deficit the less muscle-sparing effect of protein
Strategies for increased MPS
- Addition of carbohydrates to a protein meal PE: 1) serves to reverse the exercise-induced suppression of protein synthesis, and 2) helps restore glycogen stores
- Glutamine, taken alone post-exercise (PE) does NOT augment MPS
- Arginine, a precursor to nitric oxide, has NO effect on nitric oxide concentration even at large doses (10g). Nitric oxide dilates (widens) blood vessels, therefore it potentially promotes increased flow of nutrients and hormones to muscle tissues.