Theory and practice in muscle hypertrophy
We all know people who are great in theory but, despite all their knowledge, never stand out in practice. Then there are those who are fairly modest in theory yet are top performers in practice. Whichever it is, logic suggests that the best possible result should come from combining the two: solid theory and solid practice.
I want to talk to you about a piece of theory that a great many lifters try to put into practice, but do so somewhat incompletely. We’ll look at muscle fiber types, different set lengths and maximal muscle hypertrophy.
What does the theory say about the different fiber types and optimal muscle hypertrophy?
Broadly speaking, human skeletal muscles consist of three main fiber types: I (slow), II A (mixed type) and II B (fast).
Even beginners have probably heard that fast II B muscle fibers have the greatest strength and growth potential. That is true, but unfortunately most people chasing maximal hypertrophy and muscle mass apply this fact to their training incompletely. They cling to that one piece of knowledge and fail to grasp the bigger picture.
We are all well aware that to stimulate the growth of these high-potential muscle fibers, we should do 1–6 repetitions per set at an intensity of 85–100%. This theory is also true, and if we train this way, we have done everything to make sure our fast II B fibers (and, to some extent, II A fibers) get the training load stimulus they need to grow.
But the theory described above, and putting it into action, is only one piece of a bigger puzzle. Our muscles also contain type II A and type I muscle fibers. How, for example, does a five-rep set to failure at 90% intensity affect and stimulate type II A and type I fibers? Does that five-rep set also trigger substantial muscle hypertrophy in type I and II A fibers? Many people shrug at this point and don’t really know how it works. This is exactly the point that most people training for muscle hypertrophy fail to understand.
I’ll answer the questions I just posed myself: a five-rep set to failure at 85–90% intensity does not trigger substantial muscle hypertrophy in type I and II A fibers. If we push ahead with only, or mostly, shorter sets, we really do stimulate mainly the hypertrophy of type II B fibers and, to some extent, type II A muscle fibers. When we train with big and very big weights through short sets, the growth potential of type I and II A muscle fibers simply goes largely unused. This is because in short sets the duration of the tension that stimulates muscle fiber growth (type I and II A) is too short.
Although type II A muscle fibers are able to adapt to some extent to brief, high-intensity tension, the growth potential of this fiber type for sarcoplasmic hypertrophy remains unused in short, heavy sets. This is a fact that confuses many people. According to the “size principle”, we know that when we do a heavy set to failure, even just a three-rep one, all fiber types (I, II A and II B) are still at work. That is indeed the case, and without a deeper knowledge of muscle physiology the impression remains that, for optimal muscle hypertrophy and the growth of all fibers, heavy sets of three, four or five repetitions are enough. It is true that in a five-rep set to failure (and equally in a one-, two- or three-rep set) all the fiber types involved in the movement are at work, but the fact is that this same five-rep set gives the maximal growth stimulus only to the II B fibers involved in the movement. Admittedly, II A muscle fibers respond somewhat too, but only to a relatively small extent and with half the potential (especially when it comes to muscle hypertrophy).
So what happens if your goal is the fastest possible, maximal lower-body hypertrophy, and you spend most of your time squatting heavy sets of five and six? Meanwhile, the reality (which you may not even know yourself) and your genetic status may be that fast II B muscle fibers make up only 12% of all the fibers involved in your squat movements. And 34% are type II A fibers, while a full 54% of the muscle fibers involved in the squat are slow type I fibers. We want mass on our legs, yet we have only 12% type II B muscle fibers, and we keep “grinding away” year after year at 4–6 repetitions per set for our legs?
In that case you have wasted quite a bit of your potential and haven’t used your time in the most rational way. The 12% of fast fibers in this example does have the greatest growth potential, but out of all the muscle fibers in the muscles, it is a relatively small fraction. By doing short sets with big weights, we have done the best we can to load that 12%, but the growth potential of the remaining muscle fibers is largely unrealized. If we don’t also do sets of 8–25 (or even more) repetitions, the hypertrophy potential of the remaining 88% of muscle fibers (types II A and I) is largely unused. Types I and II A are indeed also at work during a four- or five-rep set, but the duration of the tension provided by the weight is nowhere near long enough to stimulate these muscle fibers to grow optimally.
Heavy weight and a short set are of course necessary to stimulate (total) hypertrophy to the maximum, but this mostly applies to type II B and II A fibers. Type II A fibers are naturally recruited and loaded during that set of five as well, but for optimal hypertrophy (myofibrillar + sarcoplasmic) the duration of such a set remains insufficient for them too. For maximal hypertrophy of type I and II A fibers, a set should last long enough for metabolic stress to build up (the relevant hormones are activated, lactate is produced, glycogen stores are depleted, etc.). Metabolic stress underlies the processes that culminate in hypertrophy, and it can only occur when a set lasts longer than five or six explosive, fast repetitions.
A favorable duration is on average 45–120 seconds, or 10–30 repetitions. To make a set last that long, or to do a set with that rep count, you will most likely need to lower the weight. That is why bodybuilders don’t do only short sets but spend most of their time (about 2/3 or slightly more of the total training volume) in the 10–30 rep range. Sets of this length create metabolic stress in type I and II A fibers, which is what induces sarcoplasmic hypertrophy.
The moral of this discussion is simple: if your goal is muscle mass (hypertrophy) and/or you train for cosmetic purposes (bodybuilding and fitness), you should organize your workouts so that, broadly speaking, a rep range of roughly 5–25 reps is covered. And as I argued, when it comes to building mass, spending as much time as possible doing short sets with heavy weight is by no means the most important thing. Unless, of course, you happen to be the same kind of genetic marvel as Alex – Edward Raus, whose muscles probably consist of a phenomenally large share of fast fibers. Squatting 320–370 kg at 20 most likely also points to near-ideal genetics (for speed-strength sports).
For us “mere mortals”, the optimal approach for building mass is to divide the rep range above into roughly four: 5–10; 10–15; 15–20 and 20–25 (there are other options too). How you work through these rep ranges in your workouts is up to each of you, whether periodized or with certain fixed ranges in every session. But over some period of time, you should make use of these ranges.
Of course, when we’re talking about functionality-oriented strength training, or strength training that athletes from other sports come to the barbell gym to do in order to improve their performance in their main sport, things are again somewhat different.
But if you are after muscle mass, then heavy basic exercises done only with short sets and big weights are by no means the most effective way for most people (the genetically average individual) to reach their goals. Think about it and take it into account!
Author: Janar Rückenberg
Source: Turg.Fitness.ee
Come and train! ArtGym
