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 are in the middle of the muscle fiber spectrum, as they are less fatigue resistance, produce more muscular force, and contract at a faster speed than slow twitch fibers. Type IIb: Fast Twitch Fibers.or recreational athletes though, commitment to practice and training will play a far more significant role in performance level than muscle fiber type alone will. So, the three types of muscle fibers are slow twitch (Type I) and fast twitch (Types IIa and IIb).