ATP -> ADP + iP + energy
One of the C-P bond in Adenosine Tri-Phospate (ATP) is broken to release energy for your muscles to work. The product is inorganic phosphate (iP) and adenosince diphosphate (ADP). Typically. the phosphate is absorbed by creatine in our body.
Normally, when we consume glucose, glucose is converted to ATP. Directly harnessing energy from gluocose isnt bad. You can see the effects of high glucose level in diabetics, especially their susceptibility to bacterial infection. Moreover, gluocose exert more osmotic pressure than ATP, so it would mean more work for our cells to maintain water content in them.
The concentration of ATP in our body isnt very high, but it's maintained at steady state because the approximately, the rate of ATP consumption equals the rate of ATP generation. Our body makes ATP by adding a phosphate to ADP through a different process. First, an enzyme release iP from one of the creatine-phosphate molecules, then energy from oxidising glucose is used to make the C-P bond to join the phospate to ADP to form ATP, ie.
Creatine-iP -> Creatine + iP
ADP + iP -> ATP
you may read up on krebs' cycle if you would like to know more.