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 II. Type II fibers are stimulated only by the degree of stretch, whereas type Ia fibers are stimulated both by the rate and degree of stretch. Gamma fibers maintain the sensitivity of the spindle, and alpha fibers stimulate extrafusal muscle fibers.