The skeletal muscle had been categorized in function of its changeable color.

Red Staple fibres: Those with high levels of mioglobina and proteins of oxygen storage had a red appearance. muscular staple fibres Red tend to have mitocondrias more and the sanguineous vases that the whites.
White Fibras: Those with a low text to have a white appearance.
To confuse still more the question skeletal muscular staple fibres also they are classified, depending on its capacity of muscular contraction, in the fast and slow muscular contraction.

Fast Twitch: Some authors define a fiber of fast contraction as that one where the miosina can divide ATP very quickly.
However, staple fibres of fast contraction also demonstrate to greater capacity of electrochemical transmission of the action potentials and a fast level of release and calcium absorption for the sarcoplasmic reticulum. The staple fibres of fast contraction to trust stated period a well developed, short glycolytic system for the energy transference and can contract and develop tension in 2-3 times the staple fibre tax of slow contraction.
Slow Twitch: The slow contraction staple fibres in the long run to generate energy for reverse speed-synthesis of ATP by means of a system of transference of aerobic energy. They tend to have a low level of activity of the ATPase, a lesser speed of contraction, with a developed capacity less glycolytic. They contain great and numerous mitochondria, and with the high levels of myoglobin that them of the one red pigmentaion that has been demonstrated that they have high mitocondriais enzyme concentration, thus, they are resistant the fatigue.