<P> Aerobic and anaerobic systems usually work concurrently . When describing activity, it is not a question of which energy system is working, but which predominates . </P> <P> The term metabolism refers to the various series of chemical reactions that take place within the body . Aerobic refers to the presence of oxygen, whereas anaerobic means with series of chemical reactions that does not require the presence of oxygen . The ATP - CP series and the lactic acid series are anaerobic, whereas the oxygen series is aerobic . </P> <P> Creatine phosphate (CP), like ATP, is stored in muscle cells . When it is broken down, a large amount of energy is released . The energy released is coupled to the energy requirement necessary for the resynthesis of ATP . </P> <P> The total muscular stores of both ATP and CP are small . Thus, the amount of energy obtainable through this system is limited . The phosphogen stored in the working muscles is typically exhausted in seconds of vigorous activity . However, the usefulness of the ATP - CP system lies in the rapid availability of energy rather than quantity . This is important with respect to the kinds of physical activities that humans are capable of performing . </P>

Where does the atp cp system take place