Energy Systems Overview

Energy systems of the body are directly responsible for providing your active muscles with a steady supply of adenosine triphosphate (ATP). ATP an important molecule composed of one adenosine with three linked phosphates (hence “tri” phosphate). Without going full Breaking Bad, energy is required to link molecules together where they’d otherwise roam free. Without linked molecules, complex matter in our world does not exist. In an exercise context, ATP functions in our body as the primary source of donated energy that causes our muscles to contract. The energy found in the bonds required to hold the ATP molecule together (three phosphate links) can be broken – releasing the energy that once held that molecule together to be used freely for other purposes.

In a previous blog I referenced a loose metaphor for how muscular contraction occurs – to reiterate:

“At the smallest individual muscle fibre level, the mechanism that causes us to be able to produce force and ultimately lift weights is based upon a synchronous, repeated, series of attachments, shortening (contraction), and release, that occurs between two microfibre subcomponents.

While an imperfect metaphor, think of someone pulling a length of rope towards themselves hand-over-hand. Within each individual muscle, one micro-fibre (the person’s hand) attaches to a second microfibre (the rope) and shortens (pulls the rope towards the body) over and over until the rope ultimately reaches its endpoint. If this example was a biceps curl, one end of the rope would be attached at the shoulder and the other would be attached at the elbow. As the hand-over-hand rope pulling occurs, the elbow bends as the muscle fibres contract and produce force.”

Using this example, each time our hand would grab, pull towards us, and release, energy harnessed from breaking a phosphate bond within an ATP molecule would be required.

We have a finite amount of ATP spread all throughout our body and thus it is necessary to find a way to ensure that it is self-replenishing in times of high demand (exercise). Each time ATP is used, one of the three phosphate links is broken leaving adenosine diphosphate (ADP) behind. The energy systems of our body work as a synergistic, supply and demand-based continuum of energy production capable of recycling these ADP molecules into ATP for continued use in exercise.

Next, we’ll dive into each of the three energy systems of interest. The phosphagen system, the glycolytic system, and the oxidative system. Each provides a significant, unique, and overlapping function in exercise which will be highlighted by future posts.

Best,

Eric