How to realize your full growth potential

Here is a brief summary

• Type I muscle fibers are considered endurance fibers and are not as important for muscle building. However, they can and should still be hypertrophied.
• You have the same muscle fiber distribution as most professional bodybuilders. They just know how to hypertrophy their type I muscle fibers.
• Wavelike periodization and back-off sets target these muscle fibers and stimulate new growth.

An overview of the different types of muscle fibers

Any inexperienced beginner coming into a gym for the first time knows that you need to focus on the fast contracting type II muscle fibers if you want to get muscular. These fibers have the greatest ability to hypertrophy and we associate them with the most muscular, strongest and hardest people in the world.

The thing is, there's plenty of room for Type I fibers to grow!

Muscle fiber distribution: not what you think

Scientists have recognized that there are many different types of muscle fiber types, but we usually organize them into three categories:

• Type I
• Type II
• Type IIb

These fibers differ mainly in the following aspects:

Nerve activity: the size of the nerve bodies and the degree of stimulation required for contraction.

Metabolic processes: Whether the fibers use primarily aerobic (oxidative processes, meaning they use oxygen) or anaerobic (glycolytic processes, meaning oxygen is not necessary) processes to generate the energy for contractions.

Capillary density: How many capillaries provide blood flow to the fibers.

Mitochondrial density: The number of mitochondria - the part of the cell that produces energy - in the muscle fiber.

Type IIb fibers: The strong guys

These are the fibers we should target for maximum gains in strength and muscle mass. These fibers have the largest nerve bodies that require a large amount of stimulation to contract. This means that you need to move something very heavy or something less heavy very quickly to bring these fibers into play.

These fibers can produce a high level of force, but they have a low capillary density and get their energy almost exclusively from anaerobic glycolysis, which means that these muscle fibers fatigue very quickly.

We often think of powerlifters, shot-putters and offensive linemen when we think of athletes with a high percentage of type IIb fibers.

Type IIa fibers: The fast guys

These muscle fibers share the same characteristics as their Type IIb brethren, but have a higher capillary density and are able to utilize oxygen for energy, making these fibers more fatigue resistant.

Type IIb muscle fibers are converted into type IIa fibers through resistance training and general conditioning. They adapt to training to develop higher capillary and mitochondrial density to last longer, but they can still produce high levels of strength and have great hypertrophy potential.

In 2008, Terzis and colleagues showed that capillary density is directly related to the endurance capacity of muscle tissue, so it makes sense that this would increase the number of type IIa fibers while they are being trained.

The body will adapt to any stimulus it is exposed to and this is a perfect example of how this works. These fibers will return to Type IIb status when the training stops, which is another example of adaptation.

When we think of Type IIa muscle fibers, we usually picture Olympic weightlifters, sprinters and baseball players.

Type I fibers: The slow guys

These fatigue-resistant fibers generally produce less force than Type II fibers. They are easily excited - meaning they contract quickly even at low levels of stimulation - and have a much higher capillary and mitochondrial density, which allows them to remain active for long periods of time.

Type I fibers are commonly associated with skinny people who practice endurance sports, but this is not entirely true. Even though these muscle fibers are resistant to fatigue, they still have a high potential for growth.

Although they have a bad reputation for not being as big and strong as their Type II counterparts, they are not the pushovers that many make them out to be.

You vs. elite athletes

Everyone has a mix of Type I, Type IIa and Type IIb muscle fibers. Yes, even Kroc and Pudzianowski have a lot of slow contracting muscle fibers. And those skinny Kenyan marathon runners that bodybuilders love to joke about have a few fast-contracting fibers.

The general rule is that people who have greater differences from normal people often end up as elite athletes.

People with significantly more type II muscle fibers have the potential to become really strong. Elite long distance runners usually have a higher percentage of type I fibers. However, most people have a reasonable mix of the different types of muscle fibers.

While many of us try to stimulate primarily the fast-twitch fibers, it would be a big mistake for anyone who wants to get incredibly strong and muscular to ignore the Type I muscle fibers. Here's why:

Illuminating research

In 2003 and 2004, Fry and colleagues rammed hollow needles into men's muscles and pulled out chunks of muscle tissue (now you know what a muscle biopsy is). They found that elite-level Olympic weightlifters and elite powerlifters had a higher percentage of Type II fibers than non-athletes. So far, no surprise.

However, these and other scientists also found that elite bodybuilders had about the same muscle fiber distribution as normal people. One of the biggest differences between the groups was that elite bodybuilders had significantly more hypertrophy of type I fibers than Olympic weightlifters and powerlifters.

This means that Arnold, Haney, Yates and even Ronnie Coleman are not the Type II machines we always thought they were. They just made their Type I fibers bigger than everyone else.

Of course, they also achieved a ton of hypertrophy in their Type II fibers, but this research showed that most of us - and you - probably have a muscle fiber type distribution similar to that of the most muscular people in the world.

Yes, you read that right. Scientists have found that elite-level powerlifters and Olympic weightlifters have a higher percentage of Type II fibers than normal people, while elite bodybuilders have roughly the same muscle fiber type distribution as non-athletes.

These studies give us a clear message: you can certainly get muscular by focusing on Type II fibers, but you can develop exceptional muscle mass by stimulating all fibers, including Type I fibers.

How to get type I fibers to grow

I'm not going to recommend that you focus exclusively on the slow-contracting Type I fibers. Programs that include heavy weights, powerlifting routines or movements performed at high speed should make up the majority of your program.

However, to use the full development of your muscles to your advantage, you should try to use two proven concepts: undulating periodization and back-off sets.

Wavelike periodization

Rather than bore you with scientific treatises on periodization, I'll tell you that all you need to know is that you'll get optimal results if you incorporate heavy, medium and lighter weights into your program.

To clarify what is typically considered heavy, moderate and light, here is a brief definition:

• Heavy: 1-5 reps, typically 85-100% of 1RM
• Medium: 6-10 repetitions, typically 70-85% of the 1RM
• Light: 10-20 repetitions, typically 50-75 of the 1RM

Wavy periodization is a fancy name for incorporating all of these weights into your program on a consistent, planned basis. For a 4 day upper body/lower body split, it might look like this:

Week 1

• Day 1: Upper body heavy
• Day 2: Lower body heavy
• Day 3: Upper body medium
• Day 4: Lower body medium

Week 2

• Day 1: Upper body heavy
• Day 2: Lower body heavy
• Day 3: Upper body light
• Day 4: Lower body light

I have used this exact system with many collegiate and professional athletes and have gotten exceptional results. As you can see, heavy weights are used more often than medium and light weights, but all are used in a systematic way.

This type of program design gives you both the heavy weights necessary to stimulate the Type II fibers and the lighter weights that are better suited to getting the Type I fibers to grow. The medium-heavy days use the time under tension - one of the factors involved in hypertrophy - to their advantage.

Back-Off Sets

In the world of bodybuilding, it's not uncommon to see exercisers moving extremely heavy weights, after which lighter weights are used at the end of the session to achieve a good pump. Although the pump itself is associated with a good workout, it may do far more for you than make you feel like your skin is about to burst.

In 2004, Goto and colleagues published a paper examining so-called back-off sets. They had one group perform 5 sets of 5 repetitions with 90% of their 1RM weight, while another group performed the same program, but performed one set with high repetitions and 50% of the 1RM weight at the end of the training session - a so-called back-off set.

The back-off set group showed significantly greater gains in both hypertrophy and strength over the course of the study. Although it could be argued that these improvements were simply the result of the increased volume, the fact remains that this approach worked better than heavy training alone.

Even if the increased volume was responsible for the improvements, the results were good enough that they should get our attention. The researchers admitted that they were not sure if it was the combination of heavy and light weights, the increased volume, the increased blood flow, or the stimulation of both type I and type II fibers that were responsible for these improvements. More research is needed to find out, but for now the exact reason doesn't matter as long as this concept works.

Taking into account what I've already presented about muscle fiber types, back-off sets seem to be an excellent way to stimulate Type I fibers at the end of a training session that has focused on the Type II fibers.

You don't need much time for this, the pump is staggering and as it's the end of the session, it's perfectly acceptable to perform a set to complete muscle failure, which could also contribute to additional stimulation of all your muscle fibers.

Train all your muscle fibers

Understanding the types of muscle fibers helps us design a program for optimal results. If you're an Olympic weightlifter or an elite-level powerlifter and you're not interested in pumped-up upper arms, then you don't need to worry about this. Stick to what you do.

However, if you're the type of exerciser who wants to build muscle mass and strength as quickly as possible, then you should take the time to build the Type I fibers that everyone has told you to ignore.

At the end of the day, you have a similar muscle fiber distribution to the most muscular people in the world and you should use this to your advantage. Instead of stimulating half of your muscle fibers, why not stimulate all of your muscle fibers?

Source: https://www.t-nation.com/training/tapping-your-full-growth-potential

By Jim Kielbaso