All muscles consist of various types of muscle fibers.  To increase strength, all types of muscle fibers should be worked during a training session.  For some specific exercise combinations that use all types of muscle fiber, read this article on an exercise plan.  Fast twitch and slow twitch are the two principal fiber categories, and fast twitch fibers are further categorized as Type A and Type B.  In nearly all of the muscles in our body, there are about 50% fast twitch and 50% slow twitch mucles fibers.  Each type of fiber works differently and to build more muscle you should have a workout plan that uses both fiber types.

Fast twitch muscle fibers work anaerobically – they are used when you need short bursts of strength or speed.  These muscle fibers use the energy stored in your body.  Fast twitch muscle fibers fatigue faster than slow twitch fibers because the fast twitch neurons fire faster.  Fast twitch muscles are exercised when a sprinter runs, using a lot of force for a very short time.

Type A fast twitch muscles are considered transitional fibers, using both aerobic and anaerobic energy to create energy.  Activities that are relatively short, but not at full speed use Type A fast twitch fibers.  Only anaerobic energy is used by Type B fast twitch muscle fibers.  They fatigue fast because they contract the fastest of all the muscle fibers.  You will use your Type B fast twitch muscle fibers when you want a lot of energy really fast. 

Slow twitch muscle fibers are aerobic.  These fibers contract slowly and do not produce a lot of force, but they are also slow to fatigue so they can work for an extended period.  Energy for these muscles is provided by oxygen rich blood transported to them through the many capillaries running through the fibers.  Low intensity exercises completed over a long period use slow twitch muscle fibers.  Running a marathon, an extended bike ride or hiking in the mountains use slow twitch muscle fibers.

 The most effective strength training program will use all three types of muscle fiber so when you want power from any given type, you will have it.  You can find reviews of programs that adhere to this principal at Turbulence Training Review and No Nonsense Muscle Building Review.   There are a lot of programs out there, but next I’ll give you some ideas on how to train each muscle type – you could easily make up your own program.

The completely anaerobic Type B fast twitch muscle fibers can be trained with exercises that require maximum effort for a short period of time.  Sprint at full speed or lift a weight that you can only do one repetition to fatigue.  Decrease the intensity and increase the time to work your fast twitch Type A muscles – run fast but do not sprint for 20 minutes or lift a weight that you can do 6 – 10 reps to fatigue.  Training for endurance trains slow twitch muscles.  Training for endurance means running longer, swimming 100 laps or lifting weights low enough so you can do 3 sets of 6 – 10 reps.  To build the entire muscle you need to be sure to train also your slow twitch muscle fibers even though this training will take longer than the training for fast twitch muscles.

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