The first process (called the phosphagen system) provides energy fastest but most fleetingly. As Bolt and I start running, our muscle cells contain barely enough ATPs to power a few steps. It seems inadvisable to stockpile so little ATP, but these organic batteries, despite being minuscule, store only one charge each, and they are too bulky and heavy for cells to manufacture and store in large quantities. You use more than thirty pounds of ATP during a one-hour walk and more than your entire body weight of ATP over the course of a typical day—an obviously impossible amount to lug around in
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