Normal levels of creatinine in the blood are approximately 0.6 to 1.2 milligrams (mg) per deciliter (dL) in adult males and 0.5 to 1.1 milligrams per deciliter in adult females. Muscular young or middle-aged adults may have more creatinine in their blood than the norm for the general population.
Types of muscle fibers. Skeletal muscle, the type that is responsible for moving our muscles when we run, is comprised of three different muscle fiber types, each with its own advantages, disadvantages, and specialty.
The muscle fiber composition of a muscle reflects actual shifts in muscle fiber type on a fiber-by-fiber basis. Therefore, unlike muscle fiber area, muscle fiber composition is a relative measurement. When the proportion of one muscle fiber type increases, another must decrease in order to make room for it.