During physical activity a subject’s performance is strictly linked to the capacity to win energy from the substracts and convey it to the contractile system of the muscular cells [En1] [En2].

Such transfer is effected through thousands of complicated reactions which can be referred to as two metabolic ways [En1] necessary to the ATP re-synthesis (adenosine triphosphate), the molecule of the nourishers which is “burnt” by the cells in order to produce energy:

• Aerobics way, in which the totality of this kind of reactions requires a continuous supply of oxygen.
• Anaerobic way , in which other reactions set free a large quantity of energy in a short time without need of oxygen. This way is essential for activities requiring a lot of power (for example sprint) and can lead or not to the formation of lactic acid (alactacid anaerobic way and lactacid anaerobic way).