In Part 1 of this series I discussed functional hypertrophy, which refers to muscle growth that improves maximal force production and non-functional hypertrophy, which refers to gains in muscle size that are not related to an improved capacity to generate force. In Part 2 I continued that discussion and got into more detail so that the difference (if there is any) between functional and non-functional hypertrophy began to become clearer. Today I would like to continue on and look at other factors and misconceptions regarding functional and non-functional muscle and strength.
One of the most common misconceptions, one that I’m guilty of being a strong believer in myself, is that lower rep, power training is what builds thick, dense muscles. The examples of this are many and that is why we are led to believe that this is in fact true. Take a look at most Olympic lifters trap development. Most have big, thick traps and necks from doing so much one rep max training, or so we have been led to believe. A possible explanation for this is that those who are strong naturally tend to gravitate towards strength sports. Remember that athletically gifted jock in high school that excelled at every sport? Well, it was a perfect fit and that’s why he chose that path. No different from the slight of build artist who had an eye for symmetry, color and shape and very little interest in sports of any kind. To some degree we are built to do what we will do best. These heavily muscled athletes of any type would likely look thick even without any training at all. I can’t count the times I’ve seen naturally massive calves on someone who looks like they’ve never seen the inside of a gym in their lives. What I’m getting at is genetics play a much larger role than does the style of training that power athletes perform.
Something else worthy of discussion is the issue of rep range and the relation to fiber type. The belief is that high rep training will build the slow twitch fibers and low rep training will build the fast twitch fibers. This is true to a degree with the exception being that no matter what you do you’re going to have a difficult time building slow twitch fibers. They just don’t have the potential for growth. What is more correct is that the type of training that you undertake can influence the quality and type of fast twitch fibers.
Muscle fibers range in color from shades of white to red. The different colors are influenced by the amount of capillaries travelling through the muscle. The slowest twitch fibers are dark red while the fastest twitch fibers are white. When reading and researching for this series I saw it best explained that the dark meat in chicken is tender (slow twitch) while the dense, fast twitch muscle in chicken is the breast, which can often be dense and tough. Then there are the various shades in between the two extremes. The redder the muscle, the more oxygen runs through it for the obvious reason of endurance. The whiter the muscle, the less oxygen, and the more anaerobic ability the muscle possesses. Although a fast twitch fiber cannot become a slow twitch fiber and vice versa, they can become a whiter or redder version of it’s former self through the correctly applied training stimulus.
Allow me to get into the science of muscle fiber types a little here so that you can see how fibers can become more favored for endurance training or instead built for hypertrophy, based on the type of training you choose. There are different sub types of fast twitch fibers, some with more endurance characteristics and some with more strength characteristics. The whiter fiber type II is known as the IIX subtype, while the light red version is known as IIA. Both of these fiber types have equal strength, but the white fibers are more explosive with little endurance (the pure white fibers have no endurance at all) and the redder fibers are slightly less explosive with a small amount of endurance.
Both of these fiber types can change into the other. It has not been proven whether this is based purely on rep range or not, but it does make sense that this would be a factor. If you are training in a way that causes muscle breakdown (in the 6 reps and over range, for argument’s sake) then this will shift your muscle fiber type towards being that of the type IIA. Basically any type of training will cause this shift simply due to the volume used. Untrained people actually have more type IIX fibers due to not having done anything with their muscle. The next time you see someone who looks like they have never trained at all remember, technically they are more so built for power than you are. As ridiculous as this may seem it is in fact true.
As I mentioned earlier, explosive athletes tend to have more IIX fibers than others do simply for the reason of genetics. It is because they begin with more of these fibers naturally that even after many convert to type IIA fibers, they are still left with more type IIX fibers than the rest of us. This is why we have been led to believe that this type of training is what leads to thick dense muscles, when in fact the opposite makes much more sense. How can training in such a low rep range that no muscle break down occurs stimulate the growth of dense muscle? It can’t.
When we next get together I’m going to look further into rep range and how we can use it to further our specific goals related to muscle growth. I’ll also wrap this series up with a few more factors that influence the growth of the fiber type that you would prefer to be made up of, depending on your goals. Until then my friends,