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.
slow oxidative fibers. This type of muscle fiber is described as red, has a slow rate of fatigue, has slow contraction, is aerobic, has a high myoglobin content, is the first to be recruited for contraction and is associated with endurance type activities.