Under normal conditions, skeletal muscle has a high turnover rate – in the range of 1-2% of muscle proteins are being synthesized and broken down daily. Without the right nutrition at the right time, any potential muscle gain from increased protein synthesis could be canceled out by protein breakdown.
Protein Synthesis Primer: It’s All About mTOR
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.
Post-workout
Muscle cells are primed for protein synthesis in the hours after training, but only if the right nutrition is there
- Only the essential amino acids (EAAs) have been shown to activate protein synthesis, with leucine being the most important
- The window is only open for a short time, and long term gains in muscle can be compromised if protein intake is delayed
The Case for Carbs
Studies have shown that insulin signaling isn’t needed to turn on training-induced protein synthesis – just leucine is required
- However, post-workout glucose consumption, although not activating protein synthesis, also had a powerful inhibiting effect on protein degradation
- Carbohydrates increase insulin levels, which may still be important
- Muscle is primed for increased protein synthesis for 24+ hours after training, but the burst in protein synthesis that occurs as a result of training or amino acid intake only lasts for a few hours
Post-workout (up to 60 minutes after training) Protein Source: 30-50g fast-acting protein: whey isolates/ hydrolysates or casein hydrolysate
Carb Source: 25-75g of medium-to-low GI carbs
- Off-season lifters or hard-gainers may want to have 50-100g of a mixture of medium to high GI carbs
Pre-workout
During training, ATP is burned to fuel muscle contractions, which increases AMP levels.
- This activates a protein called AMP kinase (AMPK), which reduces protein synthesis by inhibiting mTOR
- AMPK keeps protein synthesis machinery from getting turned off during the workout.
Wrap-up
Nutrients have a potent effect on the protein synthetic machinery, and timing them right can make or break your training progress.
Peri-workout
Carbohydrates have been shown to inhibit protein degradation, and blunt AMPK mediated inhibition of mTOR.
- Protein intake during a strength training workout resulted in an increase in protein synthesis, but much less so than when protein was delivered post-training
- This is important because insulin is a powerful inhibitor of protein degradation
How Much Protein?
Proteins act synergistically with weight training to stimulate protein synthesis, but there appears to be an upper limit to how much protein we can eat to max out protein synthesis.
- Scientists have rarely used a training stimulus that comes close to what most guys are doing in the gym, making it difficult to extrapolate and make specific recommendations.
- It’s important to experiment to find the right formula for you.
References Baar K, Esser K.
Phosphorylation of p70(S6k) correlates with increased skeletal muscle mass following resistance exercise. Am J Physiol 1999;276:C120-C127
- Protein coingestion stimulates muscle protein synthesis during resistance-type exercise. Biolo G, Declan Fleming RY, Wolfe RR
- An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. J Clin Invest 1995;95:811-9
- Skeletal muscle protein anabolic response to resistance exercise and essential amino acids is delayed with aging. J Appl Physiol 2009;106:1692-701
- Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise (Int J Sport Nutr Exerc Metab 2004;14:255-71)
The “Anabolic Window”
There are three times for increasing protein/amino acid availability to augment the acute increase in protein synthesis caused by training
- Pre-workout (within an hour or so before the workout begins):
- Peri- workout (during the training session)
- Post- workout (less than two hours post-exercise):
Pre-workout (30-60 minutes out) Protein Source: 30-50g of any medium to fast-acting protein source.
Whole-food is okay, but you may want to restrict whole-food protein closer to 60 minutes out than 30 minutes out.
- Carb Source: 25-75g of low to medium GI carbs.
Peri-workout: (during the workout) Protein Source: 10-20g of BCAAs or 20-30g of isolates / hydrolysates from casein or whey or a mixture like Plazma™ or MAG-10®
Carb Source: Optional. 35-50g of high glycemic carbs, sipped throughout the workout.
