Thought for the day: If you are thinking about how much protein you should be eating, and you accept the amino acid infusion studies as proof that amino acids cause muscle growth, then you must also accept that muscle growth can occur in a caloric deficit... unless you consider 50-60 Calories an hour a surplus.

The reason I say this is because the people in those amino acid infusion studies were fasting when they were given the amino acids. These are the very same studies that fitness marketers quote to prove that amino acid supplements cause protein synthesis and muscle growth. If a marketer is going to use research done on people in a fasted state to prove muscle growth, then they also have to admit that you can in fact grow muscle in a calorie deficit.

Muscle growth is a very interesting phenomenon. We know from anecdotal evidence from drug using bodybuilders that skeletal muscle has an incredible ability to expand in size, however, the limits and causes of this expansion are hard to measure in scientific studies because these changes in muscle size happen very slowly.

We know that exercise can cause muscles to increase in size over time, however it’s hard to show exactly how much size in a short time frame. Muscle protein synthesis increases within a few hours after a bout of strenuous exercise and remains elevated for at least 24 hours afterwards [MacDougall et al, 1995] and probably returns to normal after about 72 hours of rest [Miller et al, in press].

So the muscle building effects of exercise can last for as long as 3 days. However, it should be noted that accustomed activity only causes minor changes in muscle protein synthesis [Phillips et all 1999]. To truly cause large changes in muscle protein synthesis, the exercise must be new and novel. In other words once you get used to doing the same type of exercise, the muscles will stop adapting.

Unfortunately (or fortunately, depending on how you look at it) we adapt to exercise very quickly, so in order to stay ’unaccustomed’ we must constantly change our workout programs in exercise selection, rep scheme, rest intervals volume, intensity and frequency. These changes have to happen very frequently. A good workout program that keeps you progressing should have some minor changes from week to week, and some major changes from month to month. A workout program that doesn’t change every month wonÕt cause much of change to your body either. This is just part of how your body adapts to whatever exercise you do. The adaptations donÕt stop there either, your body also adapts to your diet and specifically to the protein and amino acids you consume.

Muscle protein synthesis also responds rapidly to eating protein, increasing within 30 minutes after an increase in amino acid availability. However, unlike the increase in protein synthesis caused by exercise, the increase caused by amino acids and protein returns to normal levels after about 3 hours, regardless of whether or not amino acids are still elevated in the blood stream. [Bohe et al 2001]

The magnitude of increase is also much smaller than found with exercise. The interaction between diet and exercise and its effects on protein metabolism seems to be additive. In other words any meals consumed in the 72 hours after a workout will determine the impact of the diet on muscle growth.

Amino acid availability is an important regulator of muscle protein metabolism. So providing amino acids during the 72 hour recovery period can potentially maximize the stimulation of muscle protein synthesis and result in even greater muscle anabolism than when dietary amino acids are not present. However, amino acid availability is not the rate limiting factor in muscle growth. Genetics and the natural amount of testosterone, growth hormone and IGF-1 seem to be the deciding factors in the amount of muscle you are able to carry, as is chronic inflammation.

Following exercise, insulin has only a permissive role on muscle protein synthesis. It appears to inhibit the increase in muscle protein breakdown without affecting muscle protein synthesis. This is partly why supplement marketers put some sort of glucose/carbs in a post workout drink mix. The idea is to use the carbs to get an insulin response to help blunt any protein breakdown that the workout might cause. Amino acids and/or protein are typically also included in a post workout powder mix in order to stimulate protein synthesis.

It is also interesting to note that the type 1 muscle fibers seem to have almost double the increase of protein synthesis that type 2 muscle fibers have in response to protein or amino acid feeding (as measured through myofibrillar protein fractional synthetic rate). However, because protein synthesis in and of itself is a very slow process anabolic response to consuming protein seems to be relatively equal among the different muscles tested.

A little known fact is that muscle protein synthesis is elevated after acclimatization to high altitudes, where resting muscle fractional synthetic rates can approach the rates normally seen after exercise or protein feeding. Thus suggesting that chronic hypoxia affects muscle protein synthesis rate (hypoxia means the body or some part of the body has inadequate or low oxygen supply). It is not believed that the observed protein turnover is driven by changes in systemic hormones such as testosterone or growth hormone, since researchers failed to find any significant changes in these hormones from see level to high elevation [Holm L, 2010]

Lastly, aging seems to induce an anabolic resistance in some individuals making them less responsive to the anabolic effects of eating protein.

The bottom line is that your genetics and choice of exercise will determine your muscle building potential and your chronic, day-to-day nutrition will aid in the process. Since muscle growth is a slow and prolonged event taking days, it is important to realize that most nutritional steps you can take must be consistent over days. No single meal is responsible for your muscle growth (this is why you can still build muscle while following intermittent fasting diets.

While there is an exciting line of researching exploring the role that satellite cells play in muscle growth, we have yet to fine any evidence that simply eating large amounts of protein will cause chronic long term increases in muscle mass. Eventually the increases stop - even with increasing amounts of protein intake.

Insulin is a hormone found in the human body that is vital in the metabolism of carbohydrate, fat and protein. Insulin is considered a storage hormone. ItÕs main effect is to cause cells in liver, muscle and fat tissue to take up blood glucose, to stop the use of fat as an energy source and promote the storage of an energy surplus in the form of body fat.



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