Nephritis is the most common cause of blood in the urine of children and young adults but it can occur at any age. If your GP suspects nephritis he will usually refer you to a nephrologist (kidney doctor).
Muscle fiber types can be broken down into two main types: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. These fast twitch fibers can be further categorized into Type IIa and Type IIb fibers, which are also known as fast twitch oxidative and fast twitch glycolytic, respectively.
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.