Muscle fiber types & your training

The Science Behind Muscle Fiber Types and How They Relate to Your Training Program
by Hugo Rivera

Muscle fiber types is a subject that unfortunately is often a neglected one. Understanding what the different muscle fiber types are, how these fibers are activated, what type of fuels they use and how fast they recover will provide you with an understanding that will enable you to create a personalized program based on the goals that you want to achieve.Muscle Fiber TypesThere are four different types of muscle fibers:

• Type I
• Type IIA
• Type IIB
• Type IIC

Type I muscle fibers are also called slow twitch red muscle fibers. They are red due to all of the blood that goes through them due to their high level of capillarization. These fibers are rugged in nature (they are not easily injured), can handle extreme mounts of work and do not fatigue easily. They require oxygen as fuel and because of this, they are the ones most used in endurance type of sports like marathon running, cycling and cross country. Type IIA fibers are fast twitch white muscle fibers. These fibers have much less blood flow in them, have a moderate tolerance to fatigue and can handle moderate amounts of work. They require glycogen as fuel and they are involved in most types of activities such as basketball, baseball and football.Type IIB fibers are also fast twitch white muscle fibers but these fibers have a very low tolerance to fatigue and need a high period of recovery after use. However, they are extremely powerful and explosive fibers and are the ones involved in activities like powerlifting, the pitch of a baseball, javelin throwing, shot putting, the beginning of a sprint, etc. In other words, anything that has a short burst explosive nature. Because of this, they use ATP/CP as fuel.Type IIC fibers are "freak type" of fibers. They are formed when satellite cells chemically bind with the Type IIB fibers. When such an event happens, this event is called hypertrophy. So by now you have probably guessed that these fibers are the ones that bodybuilders have the most. (Note: Satellite cells are cells that abound in muscle tissue but have no contractile ability. Scientists are not sure about their function but they add bulk and structural support to the muscle).On the average, most people have a distribution of 50% Type IIA fibers, 25% Type IIB and 25% Type IIC. However as you will soon see, the body has the capability to change these ratios based on the stimulus imposed. Nervous System's Ability to Change Fiber TypesBelieve it or not, recent research indicates that the nervous system has the ability to change fiber types over time based on the nature of the imposed stimulus. If the stimulus imposed is of an endurance nature, then the nervous system will change most fiber types to become Type I endurance fibers. If the stimulus is a bodybuilding type of stimulus, then the body will go ahead and start turning its II B fibers into II C fibers. Therefore, this demonstrates that the statement saying that you need good genetics to get big muscles is nothing more than a myth. The reason for this is that as long as you have the right training program, your body will adapt. Granted, one thing that you cannot control is the shape of the muscles. That is really a genetic trait. Another thing that you cannot control is how fast you gain muscle. Some people do gain muscle faster than others. However, given enough time, everybody should be able to get to their goals. So please do not let anyone put you down and tell you that you cannot excel at your activity due to genetic limitations (believe it or not, a gym owner told me once that I would never get big as I had bad genetics).Now that we have gone over the four types of fibers that we have, the ratios that the body has of these fibers and the way in which the body can actually change this ratio, let's discuss how all of this affects your training program.Training Program DesignFirst and foremost it is important to know that your training program will be determined by two things:• Your goals; activity that needs improvement (i.e. more weight lifted, more endurance, faster sprint, better golf, improved muscle mass). • The fibers involved in the activity that relates to your goal. Having said that, a marathon runner's training program will differ greatly from that of a powerlifter as one activity involves the activation of the type I fibers while the other activity involves the activation of the more explosive Type II b fibers.

Conclusion Probably the most important thing to remember about this article is the fact that regardless of what muscle fiber type distribution you were born with, given the appropriate stimulus your body will adapt and change accordingly. Therefore, never allow anyone to tell you that you cannot excel at whatever activity you like due to genetic limitations. Granted, Mother Nature is not always fair so it will be an easier road for some people than others but provided that you have the persistence and the determination necessary to excel, then you will be the best that you can be at your favorite sport by using the correct training protocol for your activity.

The table below establishes the training parameters that need to be followed based on your goals and fibers involved: