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When the satellite cells merge with the existing muscle cells to form new myonuclei this is more than muscle repair, its also the foundation for future muscle growth - beyond previous limits | more

If youve read the Intermittent Thoughts On Building Muscle (read it) you are beyond the simplistic view of muscle growth as a one-way process in the course of which muscle cells balloon up endlessly. Without the incorporation of "new" myonuclei (cell kernels) from the periphery your muscle would become dysfunctional sooner or later (learn more); and while myostatin will prevent that from happening the recruitment of new muscle cells from the satellite cell pool will provide the basis for future muscle growth.

I dont want to go into more detail, here. If you want to develop a better understanding of this process(es), I suggest you head back to the initially mentioned series about the physiological underpinnings of skeletal muscle hypertrophy.
Next to the inclusion of new myonuclei and facilitation of future muscle growth, the satellite cell pool will also provide the raw material for the repair or I should say replacement of damaged muscle cells. For strength trainees like you and me, its thus of paramount importance to ensure that our satellite cells are happy and healthy. And you know what? Thats not even difficult!

According to a recent study from the Aarhus University all it takes to  help your muscle precursor cells happily proliferating (grow, divide and mature to "real" muscle cells) is the mix of carbohydrates and whey protein youre probably consuming after each workout, anyway: A shake containing 28 g whey protein hydrolysate high in leucine (4 %) an 28 g of carbohydrate (4 %) - a 56h carbohydrate supplement served as control.

Figure 1: Overview of the experimental procedure (Farup. 2014)

As you can see in Figure 1 this supplement was not ingested once, but rather thrice a day - with the first serving being ingested immediately after the fasted subjects, 24 healthy young recreational active men,  initiated the exercise protocol, which lasted for approximately 30 min.

Its the whey that does the trick, but we dont know if we dont need CHOs as an adjunct

The provision of extra whey protein (but nor carbohydrates; white bars in Figure 2) lead to significant increases in satellite cell activity in both mixed muscle and type II fibers, but not type I fibers (not shown in Figure 2).

Figure 2: Number of satellite cells per muscle fiber (higher number = higher chance of incorporation; Farup. 2014)

Still, in view of the fact that regeneration is an energetically costly process, its not 100% certain that a certain amount of carbohydrates may be necessary to see the beneficial effects on satellite cell activity and the changes in maximal voluntary contraction force (not shown).
Reference:

• Farup, et al. "Whey protein supplementation accelerates satellite cell proliferation during recovery from eccentric exercise." Amino Acids (2014). Ahead of print.

Maximal protein synthesis requires protein, but how much exactly you need will depend on your age - the older you are the more PWO protein youll need.

Scientists from the University of Auckland were fed up with the lack of information about the differential response in protein synthesis in response to the ingestion of various amounts of protein. Accordingly, Randall F. D’Souza et al. conducted a study to characterize the changes in intramuscular levels of EAAs and BCAAs and the expression of the "protein pump" p70S6K at Thr389, a marker of protein synthesis, in response to resistance exercise and graded ingestion of whey protein in older men.

As a regular SuppVersity reader you will probably already think: "Where is the actual measurement of the fractional protein synthesis?" The unfortunate answer: Its not there.
Previous research had show that the ingestion of graded amounts of high-quality protein such as whey after resistance will maximize with "only" 20g of egg protein (Moore. 2009) or whey (Witard. 2014) in young men. Multiple studies in older adults (>60 years), on the other hand, suggest that they exhibit a lower anabolic signaling and MPS response to protein feeding, resistance exercise, and the combination of feeding and exercise when compared to young men (Cuthbertson. 2005; Fry. 2011; Burd. 2013). Scientists call this phenomenon age-related "anabolic resistance" (Yang. 2012b).

Figure 1: In contrast to the fractional protein synthesis in the elderly, which increases with increasing amounts of protein, the FSR of young men shows a ceiling effect at 20g+ whey protein (Yang. 2012a; Moore. 2009)

As you can see in Figure 1 from a 2012 study by Yang, the same 20g of extra-whey (total dose 40g) that was useless in young men, lead to a significant increase in protein anabolism in elderly men. Compared to young men, the MPS response to feeding 40 g of protein was yet still slightly lower in older vs. count men (Yang. 2012a; Churchward Venne. 2013b).

What is particularly relevant for the study at hand, and the previously criticized absence of actual MPS measurements is the fact that deficits in feeding induced p70S6K phosphorylation may at least partially underpin anabolic resistance in aged skeletal muscle (Cuthbertson. 2005), which is why measuring the p70S6K phosphorylation in older human subjects (mean age 71 years) in response to the graded ingestion of whey protein after a leg workout consisting of three sets of 8–10 repetitions of bilateral barbell smith rack squat, 45°leg press, and seated knee extensions at 80% of the subjects predetermined 1R is not as irrelevant at it may initially have seemed.

Workout + supplements, thats the "whey to go" ;-)

The exercises were performed in a circuit manner with 1 min rest between each exercise and 3 min rest between subsequent sets, the exercise protocol took approximately 20 min to complete. Following completion of the exercise protocol, subjects were immediately provided with a fixed-volume (350 mL) beverage, containing a flavored noncaloric placebo, or oneof the four doses of whey protein concentrate (10 g, 20 g, 30 g, or 40 g).

Figure 2: Intramuscular amino acids. This figure is a heat map which shows groups means fold changes from the resting fasted condition. Green represents a decrease in amino acid content, white represents no change, and red represents an increase in amino acid content (D’Souza. 2014)

Subjects were instructed to ingest the beverage within 2 min and were required to ingest the total volume provided. Following consumption of the supplements, subjects rested in a supine position throughout the 4 h of post-exercise recovery with additional muscle biopsy samples collected at 2 and 4 h post exercise.

Figure 3: Higher protein intake = higher increase in p70S6K phosphorylation (left graph). This increase is linearly associated with intramuscular leucine levels (right graph | both from D’Souza. 2014)

As you can see in Figure 3, there was a similar dose-dependent increase in p70S6K as it was observed previously for MPS in skeletal muscle of elderly subjects by Yang et al. (2012b). In fact, the fold change in the phosphorylation of p70S6K (Thr389) at 2 h post exercise was correlated with the dose of whey protein consumed (r =0.51,P<001) and was found to be significantly correlated with intramuscular leucine content (r =0.32,P=0.026).

Moreover, the intramuscular BCAAs, and leucine in particular, appear to be important regulators of anabolic signaling in aged human muscle during post-exercise recovery via reversal of exercise-induced declines in intramuscular BCAAs.
References:

• Burd, N. A., S. H. Gorissen, and L. J. van Loon. 2013.  Anabolic resistance of muscle protein synthesis with aging. Exerc. Sport Sci. Rev. 41:169–173.
• Churchward-Venne, T. A., N. A. Burd, C. J. Mitchell, D. W. West, A. Philp, G. R. Marcotte, et al. 2012. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J. Physiol. 590:2751–2765.
• DSouza, Randall F., et al. 2014. Dose?dependent increases in p70S6K phosphorylation and intramuscular branched?chain amino acids in older men following resistance exercise and protein intake. Physiological Reports 2.8: e12112.
• Churchward-Venne, T. A., L. Breen, and S. M. Phillips. 2013a. Alterations in human muscle protein metabolism with aging: protein and exercise as countermeasures to offset sarcopenia. BioFactors 40:199–205.
• Churchward-Venne, T. A., C. H. Murphy, T. M. Longland, and S. M. Phillips. 2013b. Role of protein and amino acids in promoting lean mass accretion with resistance exercise
  and attenuating lean mass loss during energy deficit in humans. Amino Acids 45:231–240.
• Churchward-Venne, T. A., L. Breen, D. M. Di Donato, A. J. Hector, C. J. Mitchell, D. R. Moore, et al. 2014. Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial.
  Am. J. Clin. Nutr. 99:276–286.
• Cuthbertson, D., K. Smith, J. Babraj, G. Leese, T. Waddell, P. Atherton, et al. 2005. Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. FASEB J. 19:422–424.
• Moore, D. R., M. J. Robinson, J. L. Fry, J. E. Tang, E. I. Glover, S. B. Wilkinson, et al. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am. J. Clin. Nutr. 89:161–168.
• West, D. W., and K. Baar. 2013. May the Force move you: TSC-ing the mechanical activation of mTOR. J. Physiol. 591:4369–4370.
• West, D. W., N. A. Burd, J. E. Tang, D. R. Moore, A. W. Staples, A. M. Holwerda, et al. 2009a. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. J. Appl. Physiol. 108:60–67 .
• West, D. W., G. W. Kujbida, D. R. Moore, P. Atherton, N. A. Burd, J. P. Padzik, et al. 2009b. Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men. J. Physiol. 587:5239–5247.
• Witard, O. C., S. R. Jackman, L. Breen, K. Smith, A. Selby, and K. D. Tipton. 2014. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am. J. Clin. Nutr. 99:86–95
• Yang, Y., L. Breen, N. A. Burd, A. J. Hector, T. A. Churchward-Venne, A. R. Josse, et al. 2012a. Resistance exercise enhances myofibrillar protein synthesis with graded intakes of whey protein in older men. Br. J. Nutr. 108:1780–1788.
• Yang, Y., T. A. Churchward-Venne, N. A. Burd, L. Breen, M. A. Tarnopolsky, and S. M. Phillips. 2012b. Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men. Nutr. Metab. 9:57.