Why is muscle growth important? There are still some that shy away from wanting their muscles to get too big, whether it gets in the way of performance for their sport or they just don’t want big muscles.

Bottom line is muscle tissue is crucial to us as humans!

Investigating ways to increase muscle is important for numerous reasons.  Recreational and professional athletes can benefit from muscle growth as a muscle with increased cross-sectional area can exert more force, eventually leading to greater strength and power potential [1].

Muscle is also important from a health perspective.  Muscle tissue plays a huge role in regulating our metabolism and consequentially all diseases that are related to it [2].

In addition, building muscle tissue in young adults could be a promising intervention to battle increasingly prevalent diseases such as sarcopenia or cachexia, which are related to muscle loss and muscle weakness [3].

How do muscles grow?

Muscle growth occurs when the total of muscle protein synthesis exceeds the total of muscle protein breakdown for an extended period of time, resulting in a positive net protein balance.

We are constantly breaking down and building up muscle proteins at the cellular level.  So, the net balance has to be positive for muscle growth to occur.  It is very well-established that in order to stimulate this process, it is essential to overload the muscle with resistance [4].

A fasted state without sufficient protein intake causes the anabolic effects that normally occur after resistance exercise to be diminished.  Basically, without adequate protein intake following resistance exercise, a negative protein balance ensues, which makes it very difficult to add new muscle tissue.


Essential Amino Acids

Essential amino acids play an important role as they increase muscle protein synthesis and minimize muscle protein breakdown, causing higher net protein balance compared with a mixture of nonessential amino acids [5].

Sufficient protein intake seems to be important to maximize the contractile protein accumulation after resistance exercise, and this seems to be partially dependent on the essential amino acid content of the consumed protein.

This is why metabolic precision recommends a first class protein such as whey protein isolate following your resistance training workouts which will help ignite the muscle building process straight away.  First class proteins contain all essential amino acids and is low in fat (less than 10g per 100g of material).

Different protein sources on muscle protein turnover and muscle size

So what are the best proteins for muscle growth?

Whey protein results in a more rapid increase and larger peak in leucine concentrations in blood and muscle than casein ingestion, likely because of different digestive properties of the proteins [6].  However, there were no differences between whey and casein in terms of their potential for muscle growth.

Research indicates that milk proteins are a better stimulator of post-exercise muscle anabolism in young resistance training athletes than soy protein.  Other research confirms that the combination of milk proteins (i.e. whey and casein) is superior to soy protein in terms of promoting muscle growth in young resistance trained individuals.

Taken together, these results indicate that a combination of milk proteins as it is naturally occurring in bovine milk is shown to be superior to soy protein in promoting muscle gains in young healthy adults [7].

When looking at the effects of the isolated milk proteins, whey protein seems to be more facilitating in the early phase after resistance exercise, whereas casein ingestion results in a slower, but more prolonged effect on muscle protein synthesis [8].

It has been suggested that the main reason for soy protein being less potent in augmenting muscle protein synthesis, despite its high-quality amino acid profile and fast digestion rate, is the way it is partitioned. Basically, it’s amino acids seem to be primarily distributed to the splanchnic region and less toward peripheral tissues like muscle [9].

Come back for Part 2 to find out more about the best proteins for muscle growth.

Connect here with WatchFit Expert Dr. Paul Henning 



  1. Maughan, R.J., Relationship between muscle strength and muscle cross-sectional area. Implications for training.Sports Med, 1984. 1(4): p. 263-9.
  2. Kelley, D.E., et al., Dysfunction of mitochondria in human skeletal muscle in type 2 diabetes.Diabetes, 2002. 51(10): p. 2944-50.
  3. Breen, L. and S.M. Phillips, Interactions between exercise and nutrition to prevent muscle waste during ageing.Br J Clin Pharmacol, 2013. 75(3): p. 708-15.
  4. Goldberg, A.L., et al., Mechanism of work-induced hypertrophy of skeletal muscle.Med Sci Sports, 1975. 7(3): p. 185-98.
  5. Tipton, K.D., et al., Postexercise net protein synthesis in human muscle from orally administered amino acids.Am J Physiol, 1999. 276(4 Pt 1): p. E628-34.
  6. Boirie, Y., et al., Slow and fast dietary proteins differently modulate postprandial protein accretion.Proc Natl Acad Sci U S A, 1997. 94(26): p. 14930-5.
  7. Hartman, J.W., et al., Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters.Am J Clin Nutr, 2007. 86(2): p. 373-81.
  8. Reitelseder, S., et al., Whey and casein labeled with L-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion.Am J Physiol Endocrinol Metab, 2011. 300(1): p. E231-42.
  9. Bos, C., et al., Postprandial kinetics of dietary amino acids are the main determinant of their metabolism after soy or milk protein ingestion in humans.J Nutr, 2003. 133(5): p. 1308-15.

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