Cell Volume and Muscle Growth
When most gym rats talk about getting bigger they are obviously referring to muscle growth or hypertrophy. Often, however they don’t really have a clue as to what’s happening within their muscles in order to make them bigger and stronger. For all they know little muscle fairies sneak into their rooms at night and when they wake up in the morning, voila, they’re bigger. Without fail, though, this never seems to stop the most ignorant of them from throwing around their lack of information with poorer form than the 20 lb dumbbells they use for “cheat” curls. And although I’m not the most brilliant guy in the world, I consider myself fairly knowledgeable at the iron game. For some reason, though, I seem to be a target for these gym “experts” as they are continually instructing me as to how to train and diet!:
What exactly is muscle growth? Hypertrophy vs Hyperplasia
To begin, I’d like to cover the two main ways for an individual to increase overall muscle size. The first, muscle fiber hypertrophy, refers to the increase in the diameter of the individual muscle cells. The larger the cells, the larger the overall muscle, it’s that simple. Muscle fiber hypertrophy = Big muscle fibers.
The second, muscle fiber hyperplasia, refers to the splitting of muscle fibers in the interest of creating new fibers. Obviously this would be of interest to anyone pursuing size or strength due to the fact that and if an individual has more fibers, their overall size potential is greater. Therefore when looking at hyperplasia, Muscle fiber hyperplasia + Muscle fiber hypertrophy = Many big muscle fibers.
At this point, I know that you’re all supercharged to learn how to both make more fibers and to make them bigger, but I’m going to have to put the breaks on and be the bearer of bad news. The problem with hyperplasia is that no one really knows exactly how to promote it. Once we are born, some experts believe, muscle fiber number remains fixed for our lifetime. Therefore under normal circumstances muscle fiber hyperplasia seems nearly impossible.
interestingly, though, experts have begun to speculate that under abnormal circumstances hyperplasia can contribute to overall muscle growth. For starters, recreational or even moderately intense weight training will probably NOT do it. Unfortunately there has not even been any evidence that very intense weight training will promote hyperplasia. One proposed link to hyperplasia, though is anabolic steroid use. A recent article in the American College of Sports Medicine’s Medicine and Science in Sport and Exercise found evidence for muscle fiber hyperplasia in anabolic steroid using powerlifters(1). This however, is pretty much the first evidence of a mechanism for hyperplasia in humans. The bottom line is that unless we are ready to boatload anabolic steroids into our systems, neither you nor I are going to be enjoying the benefits of muscle fiber hyperplasia any time soon. So what about hypertrophy? Well that, my friends, is a reality.
Two types of hypertrophy?
Let’s address the 2 main forms that muscle fiber hypertrophy can take. Muscle fiber hypertrophy can be accomplished by either increasing the volume contained within the muscle cell or by increasing the actual amount of muscle contractile protein making up the muscle cells. To give a simple analogy to help differentiate between the two types of hypertrophy, one can think of the muscle cell as a water-filled balloon. To make the balloon bigger (hypertrophy), one can either add more water to the balloon, thereby stretching it to its maximum capacity (increase cell volume) or one could theoretically add more balloon material to make the overall size of the balloon larger (increase in contractile protein). Although the mechanisms that cause increased cell volume and increased contractile protein content may be different, both are affected by weight training and there seems to be a link between the two that bodybuilders may be able to exploit in order to cause lasting muscle growth
First and foremost, when we talk about hypertrophy, we are most often referring to the second type mentioned above – an increase in contractile protein (adding more material to the balloon). This type of hypertrophy is the most lasting since it constitutes a remodeling of the muscle fibers, making them permanently bigger than before (assuming you continue to train, of course). Muscle increases of this type are not only asthetically pleasing, but also contribute significantly to strength. The more fibers available to contract, the more weight can be lifted!
But what about the other type of hypertrophy? Well let’s put it this way; how many of you wish that your muscles looked as good outside of the gym as they do in the gym after a great skin-stretching “pump”? I know that when I was younger, I wouldn’t even take one step out onto to the beach without doing some pushups first in order to “get a little blood into the muscle”. This phenomenon, the infamous “pump”, is a short-lived example of increased cell volume. Fluid moves into the cell thereby causing it to stretch, take up more space, and make you look pretty darn good. Unfortunately, such increases in cell volume disappear almost as quickly as they came. The good news is that there are other ways to increase cell volume for longer periods of time.
The increases in cell volume and their contribution to muscle growth that I wish to address are brought about by naturally by increases in cellular water; increases in the cellular storage of substrates such as carbohydrates, lipids, or amino acids; and increases in the cellular movement of ions like sodium and potassium. Research has shown that supplements like creatine, glutamine, and ribose can also lead to increases in cell volume by both increasing their own content within the cell but also by attracting water into the cell, causing cell swelling.
What’s the big deal with increased cell volume or cell swelling?
If you’ve read any of my previous articles, you know that I’m big on citing research, for without quality research, our attempts at finding out the truth about how our universe operates are merely stabs in the dark. (Kind of like Biff’s attempt at rational thought.) This research focus applied to the cell volume question has produced quite a bit of very interesting research that has and is bound to continue to dramatically impact the fitness and sports nutrition industry. Initially cell volume studies focused on the cells of the liver since the liver is the most important organ for whole body metabolic regulation.
What these studies found was that independent of hormone influence or substrate influence, decreased cell volume (cell shrinking) lead to cellular catabolism or protein breakdown, while increased cell volume (cell swelling) led to anabolism or protein synthesis. In this regard, the original authors of such papers concluded that cell swelling or shrinking acted as a “second messenger to tell the cell what to do about protein synthesis. Basically, the hormones tell the cell to swell or shrink and it is this swelling or shrinking, not the hormone’s action, that leads to changes in protein metabolism.
These findings were particularly exciting for muscle physiologists because this link could be explored in many clinical populations such as burn victims who are extremely catabolic and the elderly who tend to lose large amounts of muscle mass. Although the muscle research has mostly focused on catabolism rather than anabolism, a few important “take home” findings are evident. First is that decreased body water and intracellular nutrients can lead to cell shrinking and as we now know, increased muscle protein breakdown (7). Therefore by maintaining normal hydration and maximal substrate storage with ample fluid consumption and nutrient intake, an individual can easily prevent a great deal of protein breakdown. Also, although experimentally unproven, increased cell volume above normal hydration may lead to increases in muscle protein content. This is where supplements, especially those consumed immediately after bouts of intense exercise, come into play.
By John M Berardi