The Definitive Guide to Muscle Hypertrophy (Muscle Growth) How to Optimally Stimulate Muscle Growth By Michael Matthews You’ve probably heard that muscles can grow in different ways (“myofibrillar hypertrophy” and “sarcoplasmic hypertrophy”), and that this is related to different types of muscle fibers like Type I, Type IIa, and Type IIx. You’ve probably also heard that how you train determines the type of muscle hypertrophy that results, and that the different types of muscle fibers respond differently to exercise, and to weightlifting in particular. Is there any truth to all of this? Does it have any practical use for improving the results we get from our training? Well, let’s find out. The Different Types of Muscle Fibers Muscle tissue is a pretty complex structure, with bundles of long strands of muscle cells (known as fibers) sheathed in a thick band of connective tissue known as a perimysium. Now, these individual muscle fibers come in different types. There are three major divisions: Type I Type IIa Type IIx Type I muscle fibers, also known as “slow-twitch” muscle fibers, and they have the lowest potential for growth and force output. They are, however, very dense with capillaries and rich in mitochondria and myoglobin, which makes them very resistant to fatigue. Type II fibers, also known as “fast-twitch” muscle fibers, both a and x, have a much higher potential for growth and force output than Type I fibers, but they fatigue very quickly. These are the types of fibers we are primarily concerned with in bodybuilding. Now, we all have varying amounts of Type I and Type II fibers in our bodies, and the ratios are determined by how we use our muscles. If we did a lot of long-distance running, we would develop more Type I fibers in our legs than Type II. If we did a lot of heavy squatting, we would develop more Type II fibers than Type I. The same goes for rep schemes in weightlifting. A simple, but not incorrect, way to look at it is training in the 4 – 6 rep range mainly hits Type IIx fibers, 10 – 12 reps hits Type IIa, and 30 – 40+ reps hits Type I fibers. Simple enough. Let’s now move on to the physiology of muscle growth, and how it’s affected by different types of training. How to Stimulate Muscle Growth There are three primary ways to stimulate muscle growth: Progressive tension overload Muscle damage Cellular fatigue Progressive tension overload is, in my opinion (and the opinion of quite a few experts much smarter than me), the most important of the three. It refers to progressively increasing tension levels in the muscle fibers over time. That is, lifting progressively heavier and heavier weights. Muscle damage refers to just that—actual damage caused to the muscle fibers by high levels of tension. This damage necessitates repair, and if the body is provided with proper nutrition and rest, it will grow the fibers to better deal with future stimuli. Cellular fatigue refers to pushing muscle fibers to their metabolic limits through the repetition of actions to muscular failure. Now, you can think of these three factors as separate growth “pathways.” Each can be targeted in training, with the resulting stimulation of varying types and degrees of hypertrophy. It may have already occurred to you, but this is why natural weightlifters that focus on high-rep lifting, with little-to-no heavy lifting that gets progressively get heavier and heavier over time, fail to make any noticeable gains. They are inducing a lot of cellular fatigue, especially if they do supersets, dropsets, and other fancy rep schemes, with some resulting muscle damage, but in the absence of progressive tension overload, muscle growth is very slow. These “pump trainers” often also focus on isolation exercises, further reducing the effectiveness of their workouts (the sheer amount of muscle fibers you activate in a workout greatly affects overall growth). This is why my Bigger Leaner Stronger program is the complete opposite of “pump training.” It’s built around heavy, compound lifting that gets heavier and heavier over time, and that targets Type IIx fibers, which can grow big and strong very quickly. This type of training not only rapidly builds strength and muscle size, it results in large amounts of “myofibrillar hypertrophy,” which is one of the two types of muscle growth… The Two Types of Muscle Hypertrophy Although we don’t fully understand the mechanisms just yet, it’s generally accepted that there are two types of hypertrophy (a fancy word for muscle growth): Myofibrillar hypertrophy Sarcoplasmic hypertrophy Myofibrillar hypertrophy refers to an actual increase in size of the muscle fibers (myo means “muscle” and a fibril is a threadlike cellular structure), and sarcoplasmic hypertrophy to an increase in the volume of the fluid, non-contractile components of the muscle (glycogen, water, minerals, etc.). Sarco means “flesh” and plasmic refers to plasma, which is a gel-like material in a cell containing various important particles for life. If we look at rep ranges on a continuum going from very heavy weight for 1 rep to very light weights for 40+ reps, the following generally holds true: Heavier weightlifting preferentially increases power and induces myofibrillar hypertrophy, and lighter weightlifting preferentially increases endurance and induces sarcoplasmic hypertrophy. Researchers call this the “strength-endurance continuum.” Heavier lifting does result in some sarcoplasmic hypertrophy and lighter lifting some myofibrillar hypertrophy, but the former induces more myofibrillar than sarcoplasmic, and the latter vice versa. This too sheds some light on another big downside to working exclusively in the 10 – 12 rep range and up: You’re inducing more sarcoplasmic hypertrophy than myofibrillar, and the result is that puffy type of muscle that noticeably deflates after several days of rest. I used to train in the 10 – 12 rep range with a lot of supersets, drop sets, and giant sets, and I always hated the inflation-deflation cycle. I would train my chest on Monday and look good for a few days, but then wonder where it went come Saturday. I now have several years of heavy, 4 – 6 rep (working with 80-85% of my 1RM) lifting under my belt, and the transformation has been dramatic: These pictures represent about 2.5 years of natural, drug-free progress. And in the before, I have a post-workout pump. The after was taken on a rest day, after about 16 hours of fasting (no workout or carb pump). In the before picture, I was focusing on sarcoplasmic hypertrophy, using a lot of isolation movements (and eating a lot of food, as you can tell). I would spend about 10 hours per week exercising. The after picture was taken a couple of months ago, and is the result of focusing on myofibrillar hypertrophy. I learned how to diet in the interim as well, but as you can see, I’ve dramatically improved every muscular aspect of my body. I now spend about 6 hours per week exercising (both weightlifting and cardio). This is the power of a proper weightlifting routine. It has enabled me to build a foundation of strong, dense muscle that just doesn’t deflate. And it can do the same for you. Furthermore, focusing on sarcoplasmic hypertrophy fails to build any real strength, making you relatively weak for your size. Focusing on myofibrillar growth, on the other hand, greatly increases your strength. In my before picture, I would struggle benching and squatting just 200 pounds for reps. I can now bench in the 290 range, and squat in the 330 range, for reps. Now, don’t think that sarcoplasmic hypertrophy is totally worthless. It has a place in an advanced weightlifter’s routine, but it should not be the focus of any natural weightlifter’s training, new or veteran. But the subject of who should vary their rep ranges and why (periodization, as it’s known) is a whole other discussion, and will be fully addressed in my follow-up book to Bigger Leaner Stronger, which is titled Beyond Bigger Leaner Stronger and which is scheduled for a Q1 2014 release. So, the bottom line is the proper focus of a natural weightlifting routine is myofibrillar hypertrophy, and that means focusing on heavy (4 – 6 or 5 – 7 rep) compound weightlifting.
Posted on: Tue, 11 Nov 2014 20:54:20 +0000
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