Fast Twitch Muscle Fiber Exercises

Skeletal muscles are made out of bundled fibers that condense to contract the entire muscle. When the muscle contracts, it exerts a pull on the bone to which it is attached. Two types of muscle fibers in humans, known as Type I and Type II fibers, exert different kinds of forces, and though the muscle is always a mix between the two types, each one requires an exercise program that builds up a single type at the expense of the other.

Fast Twitch Fibers

In comparison to their slower brethren, Type II muscle fibers -- also known as fast twitch muscle fibers -- are best suited for rapid bursts of movement. They rely on anaerobic metabolism for energy and are generally bigger in size. However, they cannot be relied upon for endurance events: fast twitch fibers contain fewer mitochondria, which are the powerhouses of the cell, and use less oxygen overall. For these reasons, their purpose is to provide energy for quick, low interval activity such as weight lifting and sprints.

Strength Training

Muscular strength is developed most efficiently at five to eight repetitions of a single exercise, or until you reach failure. Each repetition should be performed near 80 percent of your maximum ability. If you are more interested in increasing muscle size with only moderate strength gains, then six to 12 repetitions will suffice. Either way, you should incorporate into your routine high-intensity exercises such as the deadlifts, bench presses, curls, triceps extensions and squats.

Sprinting

Explosive sprints of less than 400m and preferably no more than 100m will help recruit the highest degree of fast twitch muscle fibers. The best way to do this is to choose a specific distance -- for example, 50m -- and then decide on a low number of reps: perhaps three to five at one time. Each rep should be performed close to your maximum ability. After a time you may want to consider adding sled sprints, which entail dragging a weight, or hill sprints. Even hurdles are a viable way to develop fast twitch fibers.

Plyometrics

Plyometrics is the name given to a set of exercises that develop explosive movements through the nervous system by lengthening and then contracting the muscles in rapid sequence, usually involving some kind of jumping or exaggerated movement. For example, exercises may include hopping repeatedly into the air from the tiptoes, jumping over cones or foam barriers, power skipping, bounding and "butt kickers," in which the back foot is raised as high as possible behind you. You can even toss around a heavy medicine ball to develop explosive power in the arms.

Considerations

Two types of fast twitch fibers exist: Type II A fibers and Type II B fibers. Type II B fibers rely exclusively on anaerobic metabolism for energy. Type II A fibers, on the other hand, also have attributes of Type I fibers. If you want to build Type II B fibers, then you should focus exclusively on explosive, low-interval exercises. Type II A fibers are utilized for more moderate exercises.