Energy Systems Explained

29 May 2011

Energy Systems Explained - Overview

In previous posts (part I, part II, part III), we dealt with energy intake and storage within the human body. In this upcoming series, we will explore the next chapter of the energy utilization process by discussing the different energy systems which make up human metabolism.

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All movement by the human body requires energy. In the case of voluntary movement, this energy comes from the food we eat. As previously noted, ingested food is broken down and digested, and then funneled into one of the several energy storage forms that we use (ie…glycogen or body fat). This energy is then mobilized from its storage state and used to power everything from wound healing to pull-ups.

It is important to note that no matter what the activity in question, muscular contraction is powered by only molecule…Adenosine Tri Phosphate (ATP). For this reason, ATP is known as the "energy currency" within the cells.

We store enough ATP to last just a few seconds of an all out exertion. Therefore, immediately after use, used ATP (at this point called Adenosine Di Phosphate, or ADP) is regenerated into a brand new ATP molecule ready to power muscular contraction again.

Due to ATP being the only direct fuel for muscle, it is the end point for every energy system. In other words, regardless of which energy system is being used, ATP will be created, and then used to power muscular work. The difference between the energy systems is not what is being created (always ATP), but how long it takes and how much ATP is being created.