by Mike Arnold
There has been a lot of talk in the bodybuilding community over the last few years regarding the role of workout-based insulin and for good reason–it is the single best time one can use the drug to promote recovery & growth, but what exactly makes it so effective…and more importantly, how can we maximize our results with this approach? Of all the subjects I have touched on over the years, nothing else has even come close to generating such a large amount of interest from so many people. With this in mind, I have decided to address some of these unanswered questions not only to validate this particular method of administration, but to clear up any misconceptions which arose as a result of my former writings on the topic.
Why is Workout-Based Nutrition so Important?
In order to maximize recovery & growth while minimizing fat gain, one must do more than just shove a ton of food down their throat at regular intervals. Everything we eat should be done for a reason—with a purpose in mind. A haphazard approach may suffice for some, but for those who want to make the most of their physique, there is no room for half measures or senseless diet plans.
Nutrient repartitioning plays a vital role in determining what kind of results we will get from our bodybuilding diet. Only by directing the nutrients we eat to the right place at the right time can we ever hope to make the most of our BB’ing efforts. We can accomplish this by manipulating certain factors such as food timing, type, and quantity, as well as drugs, training, and supplementation, among others. The point here is that the body’s dietary needs, as well as its ability to use the nutrients and drugs we provide it, is in a constant state of flux. Therefore, we need to anticipate these needs and take advantage of each opportunity that presents itself, if we want to maximize our rate of progress.
The training window is one such opportunity. For a few hours a day, which begins at the onset of training and continues until a couple hours afterward, the nutrients we consume are preferentially shuttled towards muscle fiber and away from adipose tissue, while the processes involved in glycogen restoration and protein synthesis up-regulate. By taking advantage of this enhanced physiological state via nutrition, pharmacology, supplementation, etc, we can greatly accelerate the recovery & growth process. Not only will this allow us to grow more from each individual workout, but it may also enable us to increase our training frequency, accelerating muscle growth on two fronts. For this reason, the training window is largely considered the single most important time to facilitate nutrient delivery and has been adopted by most as an integral part of BB’ing nutrition.
When it comes to workout-based nutrition, most guys keep it rather simple. For the majority, this entails consuming some form of fast-digesting protein and carbohydrate after training and calling it a day. Some guys will even take things a step further by employing pre, intra, and post-training nutrition-supplementation. While most guys are aware of the primary benefits associated with this approach, a much smaller percentage understand why these things are important. We already know the short answer to this question would be that the body responds more favorably to nutrients at this time, but this limited explanation doesn’t provide us with the information necessary to further capitalize on this naturally occurring opportunity.
This subject can get quite complex, so we will limit this discussion to the two primary physiological changes which takes place during the training window and which are responsible for powering the majority of it positive effects. These are an improvement in insulin sensitivity and perhaps more importantly, increased in Glut-4 expression (more on that in a minute). Being directly responsible for the extent and rate at which nutrients are transported from the bloodstream into the muscle, their ability to regulate muscle growth by controlling both glycogen replenishment and protein synthesis cannot be understated. Therefore, anything we can do to augment these processes will allow us to receive greater benefit from both our nutrition and insulin use.
While weight training leads to a natural increase in insulin sensitivity and Glut-4 expression, it is only one of several factors which have a positive effect in this area and which can be manipulated to our advantage. Realistically, there are dozens of actions we can take to further amplify insulin sensitivity and Glut-4 expression within muscle tissue, but first, we need to know what Glut-4 actually is and how it works together with insulin to stimulate muscle growth.
Glut-4 and Its Relationship to Insulin
Technically, Glut-4 is a transporter protein that helps facilitate the transport of glucose across cell membranes for use by the cell. It is active in tissues such as the heart, adipose tissue, and skeletal muscle. It belongs to a family of 13 similar proteins, but only Glut-4 and Glut-1 are relevant to this discussion, as they are the primary transporters in muscle tissue. Of the two, we will choose to focus solely on Glut-4, as Glut-1 is present in much lower quantities and is also insulin independent, which precludes it from manipulation in the same manner as Glut-4.
Widely recognized as “the” nutrient transporter, insulin works in tandem with the less popular Glut-4 to deliver nutrients to the muscle cell. Here’s how it works. After we eat a meal, glucose and aminos acids are liberated from the food we ate and released into the bloodstream, resulting in an increase in blood glucose and amino acid levels. As soon as the body senses this increase, which takes places almost immediately, the pancreas responds by releasing a corresponding amount of insulin into the bloodstream, which then acts as a transporter, shuttling glucose, aminos, etc, to the muscle cell for delivery. However, while aminos acids may be present along with glucose, only glucose stimulates the release of insulin into the bloodstream.
Some mistakenly believe that it is insulin which delivers nutrients into the muscle cell, but this is not the case. Rather, it only brings them to the cell membrane (cell surface), at which point Glut-4 transporters take over and transport these nutrients into the cell itself, where they can then be used for recovery & growth. So, both insulin and Glut-4 are “transporters”, but their functions are different, with each one playing a unique and vital role in the delivery of nutrients.
Sounds simple, right? Well, not quite. When in an inactive state, Glut-4 resides in an intracellular compartment within the muscle cell, hibernating, so to speak. Before it can transport nutrients into the cell, it must first leave this resting chamber and rise to the cell surface. Only then can it perform its function of transporting nutrients into the cell. However, the amount of Glut-4 which comes to the cell surface can vary tremendously depending on a number of factors. With Glut-4 involved in the muscle growth process on such a fundamental level, common sense dictates that anything which down-regulates Glut-4 expression will have a negative impact on muscle growth, while anything which up-regulates this transporter will have a positive effect.
Obviously, the goal of every BB’r should be to maximize this aspect of nutrient delivery, but before we are able to do that, we must first know how Glut-4 expression is regulated. One of the most influential regulatory factors is insulin itself, but the relationship between the two is unstable, as insulin has the ability to both up-regulate and down-regulate Glut-4 expression depending on the circumstances. Confused? Keep reading.
You see, when insulin attaches to the insulin receptor, which is located on the surface of the muscle cell, it signals Glut-4 to rise to the cell surface, so it can perform its job. However, when the insulin receptor becomes over-exposed to insulin as a result of insulin resistance or the chronic overconsumption of carbs (particularly refined, high glycemic carbs), Glut-4 expression is stunted. Basically, they refuse to come out and play, leaving all our valuable glucose and aminos acids outside the cell and unable to promote muscle growth. Insulin will always maintain the ability to initiate Glut-4 expression to at least some degree, but overexposure can and certainly will limit it. Because of this, insulin resistance should be avoided at all costs.
Glut-4 expression can also be affected by a variety of non-insulin dependent pathways, some of which we can be manipulate in our favor. In the following article we will discuss the different methods one can use to improve our insulin sensitivity, while also learning how to up-regulate Glut-4 expression via non-insulin dependent pathways.