1 Chemically, ATP is an adenine nucleotide bound to three phosphates. 2  There is a lot of energy stored in the bond between the second and third phosphate groups that can be used to fuel chemical reactions. 3  When a cell needs energy, it breaks this bond to form adenosine diphosphate (ADP) and a free phosphate molecule.
calf muscle pump. calf muscle pump. an action of the calf (soleus) muscles in which the muscles contract and squeeze the popliteal and tibial veins, forcing the blood in those veins to move upward toward the heart. Also called soleus pump.
Okayâ¦Back to âThe Pumpâ. The simplest explanation of the pump is that more blood is forced into the working muscles causing the muscles to swell a bit. The reason this helps for muscle growth is that the muscles are surrounded by a tissue called the fascial layer.