Muscle groups in the body are comprised of two types of fibers: Slow-twitch and Fast-twitch. Understanding the difference between the two, as well as the training methodologies which lead to successful training of each area, will lead to the recruitment of the highest possible number of fibers, and should be very important to bodybuilders! Slow-Twitch The first kind is Type I fibers, or slow-twitch muscle fibers. These fibers have very strong aerobic ability for oxidation, they contract very slowly, and they are very useful in endurance activities. These muscle fibers are “hit”, or engorged with nitrogen-rich blood, during higher rep training, specifically in sets of 12 to 20 reps. This type of training is often neglected by bodybuilders. Fast-Twitch This group of muscle fibers is called Type II, and is considered to be of the fast-twitch variety. These fibers assist with ...

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