Insulin and Muscle Growth

I have always been aware that there is a link between Insulin and muscle growth. But for those of us who are not scientists, it's hard to get a simple explanation. The following are excerpts from 2 articles found here:
http://www.ast-ss.com/research/cribb/insulin_and_muscle_growth.htm
http://www.ast-ss.com/research/cribb/precision_supplement_timing4.htm

I encourage you to visit that site if you want the full text.

Insulin and Muscle Growth.
The Latest Research.

By Paul Cribb B.H.Sci.HMS. Exercise Physiologist


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There’s been a quite a few articles written about the anabolic effects of insulin in various magazines over the last few years and with good reason. Manipulating this "anabolic" hormone and making it work for you is critical to muscle growth. Nothing really substantial occurs without it. Insulin is the anabolic activator.

Instead of going through a whole internal anabolic and hormonal physiology lecture, I’ll sum up the action of insulin in a few sentences. Then I’ll present you with the latest information that explains, in simple terms, the intricate mechanics of this incredibly potent muscle building hormone. I’ll show you how to make insulin work for you so you can take your physique beyond your greatest expectations. Best of all, it’s backed by science. See for yourself.

Many bodybuilders and other athletes choose to use external sources of insulin in their chemical arsenal of supplements - yes they inject it. Exogenous insulin is completely undetectable by current drug testing procedures. If I were shooting for a gold medal and all that goes with winning it, I might (I said might) see the logic. However, death by exogenous insulin induced hypoglycaemic coma isn’t really appealing to me, especially when manipulating your body’s own insulin levels is remarkably easy, safe, and an extremely effective way of accelerating muscle growth.

What Does Insulin Do?

It has been well known for a long time that insulin plays a major role in regulation of protein body mass. Prior to its clinical availability, patients with Type I diabetes experienced continuous loss of protein from all tissues until they died. After its introduction it was apparent that treating of these patients with insulin dramatically restored muscle mass. Now as we discuss protein and muscle metabolism, it is important to keep in mind that both protein synthesis and degradation proceed simultaneously at all times. And that net protein metabolism (muscle gain or loss) is regulated by a increase/decrease of either or both of these processes.

The Muscle Building Mechanisms of Insulin.

Recent human invivo research has revealed that insulin exerts its dramatic anabolic effect by inhibiting muscle breakdown/degradation and not stimulation of protein synthesis as invito (isolated cell cultures ) studies once indicated. (This is an important point, remember this as we will apply it later.) This process is believed to occur by the inhibition of the ubqitin-proteasome pathway (one of three major muscle degradation pathways in muscle cells). But once again, little is known about the cellular mechanisms by which insulin exerts this anti-catabolic action (just another example of how complex human physiology really is!) However, research does show that the introduction of insulin stops muscle breakdown (proteolysis) dead in its tracks and reduces net protein loss to zero. Also, while insulin is driving amino acids and glucose into muscle cells, it appears it also prevents the "leaking out" of these nutrients from the muscle cells that usually occur in response to training or illness.

The presence of insulin locks in all the vital components of muscle growth. Kinetic studies using amino acid tracers confirm insulin is a potent amino acid transporter. In the presence of insulin, blood plasma levels of amino acids disappear. They are being driven into the cell and thus little is detected in the blood. However, as soon as insulin is taken away, blood plasma amino acid levels increase fast!1,4,8 They are being sucked out of muscles and utilized by other organs to meet their ravenous metabolic demands. When this is happening it is physiologically impossible for muscle protein deposition to occur! Muscle will not grow! Absence of insulin or allowing insulin levels to drop is the fastest, easiest way to induce muscle protein breakdown (catabolism). Let me explain how this relates to your training.

Research demonstrates the catabolic response to weight training is so great it may equal or even surpass anabolic (muscle building) mechanisms and produce net zero gains in muscle mass. Therefore, directly after training you are in potential trouble. You must get insulin levels up quickly to counteract the enormous protein degradation that will and does occur. Recent research reviews demonstrate that an optimal hormonal environment must be created after training for muscle deposition (muscle growth) to occur. Athletes and experts who think they are in the know about building muscle assume that just eating and drinking something after training should cover this objective. However, if you examine the literature closely you will see, as I did, there is a lot more to igniting muscle growth than that!

First, studies on insulin’s effect on accumulation of creatine in muscle reveal some important points. Insulin concentrations close to upper physiological limits (above 100Mu/l) are required to maximize creatine uptake and no less than 100 grams of simple carbohydrates must be ingested with creatine to enhance the uptake! And, this dose proved to be close to the limit of palitability! 100 grams of simple carbs made into a sickly-sweet drink optimized creatine uptake into muscle cells.

These two important aspects point toward the fact you may have to ingest a greater amount of simple carbohydrate after your training than you are currently using to take advantage of this potent, muscle building process. The 3 hours after training is the critical time to maximize cellular transport by elevated insulin levels. And you can actually determine how much creatine and amino acids you want in your muscle cells!

Insulin Needs Amino Acids to Build Muscle

Research reviews have determined that insulin halts protein breakdown, but does little to stimulate increases in protein synthesis rates. Insulin research also demonstrates an abundant supply of amino acids must be present along with high insulin levels to produce net gains in muscle. In fact, the whole stimulatory effect of insulin on muscle anabolism is dependant on a large, plentiful amount of amino acids to stimulate protein synthesis rates that create increases in muscle! This means a rapid, easily assimilated source of amino acids must be there at precisely this time.

Once muscle cells are crammed with these important nutrients they have to be kept within the cell to continue to exert their powerful muscle building effects. This means two objectives have to be met. Insulin levels have to be kept constant and a continuous, easily assimilated supply of amino acids has to be present in the blood stream to meet the metabolic demands of all other organs in the body so they won't draw them from muscle tissue! This is an important job of a protein supplement most people don’t even consider. You have to give your body the right material all the time so it doesn't rob important nutrients from muscle tissue!

These two objectives can be easily achieved by combining protein with carbohydrate in small, very regular meal intervals throughout the day and night. However, food sources must be easily and rapidly assimilated. This is why alternating solid, fiber rich meals with (meal replacement drink) provides superior nutrient absorption kinetics that cannot be achieved with whole food sources alone.


Step by step lets look at how this is done in a normal day's training.

First, muscle cells must be depleted as much as possible via hard training.

10 minutes before finishing training, ingest a 5 gram serving of Creatine with 30g of Carbs.

Then, within 10 minutes after training introduce a large amount, approximately 75gms of simple carbs with another 5 mg serving of micronized creatine and a rapidly absorbed protein.

Within an hour after training eat a small solid-food protein/carb meal.

Then repeat step three again (with or without the creatine) within the two hour mark after training to really take advantage of this accelerated cellular uptake that is happening only during this time frame.