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.
The fast-twitch muscle fibers are known as the white muscle, while the slow-twitch muscles fibers are known as red muscle. These two types of muscle fibers are engaged differently depending on what type of activity you are doing.lite sprinters may have up to 80% more white muscle fibers than red since their performance relies on this type of tissue. White muscle fibers fatigue at a much faster rate than their red counterparts because of a buildup of lactic acid, so they are only good for short bursts of speed.