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.
1 Strength training induces hypertrophy (increase of muscle fiber size) of both type I and type II fibers, however it results in decreased mitochrondrial mass of skeletal muscle.  Combining endurance training with strength training is key to maximizing your muscles power and resistance to fatigue.