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.
Type II muscle fibers, also called fast-twitch, are large muscle fibers used for lifting heavy loads. A weight lifter has an abundance of type II muscle fibers. Competitive sprinters also have plenty of type II muscle fibers in their large leg muscles, which are used to produce strong movements for a short time.