All About Muscle Fibers

You may have remembered me mention in the past that we all have different kinds of muscle fibers. The topic today is going to go into a little more detail of what each of those different muscle fibers are and how they relate to the Lean Body Fat Loss Training program.

1. Type I muscle fibers (aka slow twitch muscle fibers) – These fibers develop force very slowly and at the same time, relax slowly and can withstand fatigue for long periods of time. These types of muscle fibers have a high capacity for activities such as a marathon, soccer and distance cycling. Basically, you are going at a sub maximal pace for a long period of time. These fibers are used in what is classically called “endurance” exercises and activities.

2. Type IIa muscle fibers (aka fast twitch muscle fibers) – These fibers can develop force faster than the type I fibers but, also get fatigued faster. These fibers involve activities that are a little more quicker and powerful with intensity than the type I fibers, such as an 800 meter run, some strength training workouts like in Lean Body Fat Loss Training Program and interval training.

3. Type IIb muscle fibers (aka fast twitch muscle fibers) – These are the most powerful muscle fibers that we have. These are the fibers that are able to develop force very rapidly, but, at the same time, they fatigue very rapidly. These include activities such as a 100-m sprint, a maximal lift of a weight, or a vertical jump.

So what does all this mean for fat loss? One other piece about these fibers is they’re recoverability after the activity is complete. Remember, type I muscle fibers don’t fatigue easily. So if you go out for a run at a steady slow pace, you’re mainly using type I muscle fibers and they aren’t “damaged” that much during the process and thus, recover rather quickly after the activity is complete. When using type I fibers, you don’t burn that many calories afterwards in order to “repair” them.

The type II fibers (both types) are a different story. They fatigue very rapidly and they don’t recover as quickly as the Type I fibers. So if you were doing a barbell squat and lifting as much as you can, you should be able to only lift it once. This is very taxing and those high power type II muscle fibers fatigue almost instantly. You’ve caused “damage” to those muscle fibers and your body is going to need to use energy in order to “repair” those muscle fibers.

This is the reason why weight training and intervals and other high power activities are good for fat loss. You will burn more calories after the workout in the repair phase than you would if you were doing longer, less intense activities that only use type I muscle fibers.

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