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Fast Twitch and Slow Twitch Muscle Fibers

There are primarily two different types of muscle fibers. They are type I and type II. Type II fibers are also known as slow-twitch and type II are also known as fast- twitch fibers. There are also two kinds of type II fibers. These are type IIx and type IIa. The reason that I mention all of these fibers is because they should be trained properly throughout the course of our workouts. However, that’s not to say that each fiber should be focused on for each workout. Some of our workouts will focus on type II fibers, some will focus on type IIx and some on type IIa. Most workouts will involve a using a combination each of these fibers, but one type is typically focused on at a time.

Not everyone is going to want to train in the same way because everyone has different goals.The goals of a bodybuilder are mainly directed toward building bigger muscles and maintaining a low body fat. In order to build their muscles to their full potential, bodybuilders train all types of muscle fibers. However they usually focus on the type II fibers rather than the type I. I like to reference bodybuilders because I feel that we owe them a lot for the current fitness revolution. At the same time though, their training regimens are responsible for a lot of the problems that we have with today’s idea of fitness. A bodybuilder’s routine is suited to his or her specific goals. Before starting any training program, consider your individual goals first.

Some people want big muscles, and some people just want bigger muscles than they currently have. And then again, many people have goals that have nothing to do with building huge muscles. They just want to be in better shape, have more energy, and live longer. Athletes especially have very specific goals as well. Athletes usually sacrifice muscle size so that they can be stronger, and faster while maintaining their current weight. Of course that isn’t always the case. Many athletes such as an offensive lineman or a sumo wrestler prefer to have tremendous size as well as strength. Unlike a bodybuilder, they rarely need to worry about reducing their body fat. On the flip side, athletes that compete in specific weight classes such as boxers, wrestlers, and Olympic weight lifters are careful not to gain too much muscular size.

Speaking of Olympic weight lifters, they are a great example of athletes that work their type IIx muscle fibers more than the other types. This is because type IIx fibers provide more force than the others, and Olympic weight lifters need to be able to lift very heavy weights for low repetitions. Power lifters and sprinters train in much the same way. This is why we often notice that those kinds of athletes have more muscle than the average person but usually not as much as a bodybuilder might have.

The point that I’m trying to get by with all of this information is that we can decide which fibers we need to train the most to get the goals that we want. Type I muscle fibers are the kind that have the best oxygen delivery which is one of the many reasons that our bodies use them for endurance. Endurance athletes rely heavily on the training of their type I muscle fibers. This kind of training usually gives the athlete a very lean and muscular look, but the muscles are toned rather than large. Just look at guys like Lance Armstrong. Whether he used performance enhancements or not, that guy is a tremendous athlete. He is very lean, and his leg muscles are slightly larger than average because he has trained them a lot. Training type I fibers does result in an increase in muscle size but not nearly as much as training type II. And I may be wrong, but I believe that Lance Armstrong is one of those smart athletes that often integrates other types of training into his routines. By observing different types of athletes we can get a more clear idea as to how we want to train our own bodies. So be on the lookout for the kind of body that you want and then try to discover what kind of exercise makes that person look the way they do.

About Jake Long
In late 2014, Jake co-founded FitnessJunkies.com with his brother Ryan. Jake is a NASM certified personal trainer and has been blogging on health and fitness since 2011 when he started JakesHomeWorkouts.com.