Fast and Slow Twitch Muscle Fibers-Type IIa Fibers

It is generally accepted that muscle fiber types can be broken down into two main types:slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. Fast twitch fibers can be further categorized into Type IIa andType IIb fibers. Type IIa Fibers These fast twitch muscle fibers are also known as intermediate fast-twitch fibers. They can use both aerobic and anaerobic metabolism almost equally to create energy. In this way, they are a combination of Type I and Type II muscle fibers.