Various types of muscle fibers form each muscle. When all types of muscle fibers are exercised the muscle is strengthened. For some specific exercise combinations that use all types of muscle fiber, this article on a workout plan. Fast twitch and slow twitch are the two main fiber categories, and fast twitch fibers are further categorized as Type A and Type B. In the majority 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 training program that uses both fiber types.
Fast twitch muscle fibers work anaerobically – they are exercised when you need short bursts of strength or speed.  Anaerobic means they move using the energy stored in your body. The neurons in fast twitch muscle fibers fire more rapidly, so the fibers fatigue more rapidly, than slow twitch fibers. Sprinters use fast twitch muscles because they use a lot of power for a very short time.
Fast twitch Type A muscle fibers are transitional fibers and use both aerobic and anaerobic energy. These muscle fibers are used for activities that are relatively short, but not at an all out pace. Only anaerobic metabolism is used by Type B fast twitch muscle fibers. They fatigue very fast because they contract the fastest of all the muscle fibers. You will use your Type B fast twitch muscle fibers when you need a lot of energy really fast.Â
Slow twitch muscle fibers are aerobic. These fibers contract slowly and can work for a long time, but they do not create a lot of strength. There are a lot of capillaries throughout these muscle fibers to provide oxygen rich blood for energy. When you need to complete a low intensity exercise for a long period of time you use your slow twitch muscle fibers. Slow twitch muscles are used when you train for a marathon, ride a bike many miles or go hiking.
 The most effective strength training program will use all three types of muscle fiber so when you require 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 very short time. Lift the heaviest weight you can lift for one repetition to fatigue or sprint at full speed to fatigue.  Type A fast twitch muscles are worked when you lower the strength required and increase the time – run fast for 20 – 30 minutes or lift a weight that allows you to complete 6 – 10 repetitions to fatigue. Slow twitch muscles are strengthened when you train for endurance.  Lift weights small enough that you can complete 3 sets of 6 – 10 repetitions, run for an hour or swim a lot of laps. This training will take longer than training for fast twitch muscle fibers, but it is necessary to do this training also to build the entire muscle and get the maximum strength you are looking for.