Nowadays, everyone who does strength training knows that they need to consume a lot of dietary protein for muscle hypertrophy. But also old people, who want to maintain their skeletal muscles need to consume an increased amount of dietary protein. Because maintaining skeletal muscle mass throughout the lifespan is critical for the preservation of metabolic health and independent locomotion. While central to the production of contractile force, skeletal muscle also serves as the primary site of postprandial glucose disposal and is the largest contributor to resting energy expenditure. But this article mainly focuses on muscle hypertrophy.
There is now a wealth of studies that have characterized the response of skeletal muscle to changes in nutritional and contractile stimuli. What these studies have shown is that the size of skeletal muscle is dependent upon the kinetic processes of muscle protein synthesis (MPS) and muscle protein breakdown (MPB), the algebraic difference (MPS minus MPB) between which dictates net protein balance (NPB). When diurnal fluctuations in MPS equal those of MPB, muscle mass is maintained. Muscle protein accretion leading to the growth of muscle fiber size is only achieved when net rates of MPS exceed MPB and NPB is positive. But it is very important to consider that there is also an upper limit for protein intake. So, don´t consume too much protein over the day! Alternatively, net muscle catabolism (atrophy) leading to the loss of muscle proteins, occurs when MPB exceeds MPS and NPB is negative. So it always depends on your goal.
Also, pre-or post-exercise ingestion of protein (PRO) or essential amino acid (EAA) can increase MPS and result in a positive NPB. Furthermore, the majority of studies in humans suggest that PRO/EAA ingestion in the context of a resistance training session can enhance skeletal muscle hypertrophy in response to chronic resistance training. More specifically, PRO/EAA intake around the time of resistance exercise, as opposed to nutrient ingestion at times distal to exercise, maybe more beneficial for promoting muscle hypertrophy. In the diagram below you will see how different consumption of protein will affect your MPS. In addition, the diagram also shows whenever you consume dietary protein your MPS will increase which leads to a positive protein balance which in conclusion is necessary for muscle hypertrophy.
Figure 1 Muscle Protein Synthesis and Breakdown (Source: https://www.researchgate.net/profile/Stuart-Phillips-2/publication/333356168/figure/fig3/AS:762130420740101@1558717460792/Muscle-protein-synthesis-MPS-and-muscle-protein-breakdown-MPB-in-responses-to-grams.png; Retrieved on 13.09.2021)
But before we look at recommendations for protein intake, you need to consider that more protein may be required to maximize the response of MPS with less than optimal protein sources (i.e. vegetable protein) and/or with older individuals. So, ingestion of a high-quality protein within close temporal proximity of exercise is recommended to maximize the potential for muscle growth. Now, you will get a recommendation for your protein intake depending on your goal.
Individuals in Energy Balance
Consume ~0.4 g/kg body mass per meal, to maximally stimulate MPS
Spacing protein-containing meals ~3–5 h throughout the day maximizes MPS rates over the course of a 12 h (i.e., waking) period.
Practice pre-sleep protein ingestion (1–3 h prior to sleep) to offset declines in MPS that would occur during an overnight fasting period.
To maximize muscle protein accretion with resistance exercise, daily protein intakes should be ~1.6 g/kg/day and up to 2.2 g/kg/day. This intake can be achieved by ingesting 3 meals, each containing ~0.53 g/kg protein, or 4 meals containing ~0.4g/kg protein.
Periods of energy restriction result in significant reductions of lean body mass (LBM). Lean individuals, and those with more training experience, appear to be more susceptible to reductions in skeletal muscle size relative to heavier, training-naïve individuals. Reductions in LBM are primarily driven by reductions in postabsorptive rates of MPS and reduced sensitivity to the presence of a protein bolus. To effectively prevent these declines in MPS during both postabsorptive and postprandial periods, daily protein intake has been recommended to be increased, and leaner athletes may wish to aim for intakes at the higher end of this range. You find some recommendations below:
Individuals in Energy Restriction
Daily protein requirements are greater than they are during periods of energy balance to promote the maintenance or increase in lean body mass.
Resistance exercise should be performed during energy restriction to promote the retention of lean body mass if desired.
For athletes ‘cutting’ weight over an extended period, high-quality protein sources such as whey and casein, or a blend of each, should be chosen to optimize appetite control and ensure dietary compliance.
To promote lean body mass retention during weight loss, protein intakes of ~2.3–3.1 g/kg/day have been advocated.
So you have seen, how important it is to maintain a balanced dietary protein intake. On Thursdays, you will also get a nutrition plan with the most common animal and plant-based protein sources. So, don´t forget to check out the post on Thursday we see us then.
Hulmi, J. J., Lockwood, C. M., & Stout, J. R. (2010). Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutrition & metabolism, 7(1), 1-11.
Stokes, T., Hector, A. J., Morton, R. W., McGlory, C., & Phillips, S. M. (2018). Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy with resistance exercise training. Nutrients, 10(2), 180.
Tipton, K. D., & Phillips, S. M. (2013). Dietary protein for muscle hypertrophy. Limits of Human Endurance, 76, 73-84.