Estimated read time: 9 minutes + videos
If you have a background in exercise physiology, have been to a level one certification, or remember the CFJ article What is Fitness, then this discussion of energy pathways will probably look familiar to you and hopefully provide some further insights and topics for reflection.
If you don’t have any interest in physiology, then this may bring back nightmares of your biology or biochemistry classes.
The graph below shows the three primary energy pathways and ~ how much they contribute during activities of various intensities and duration.
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| Graph courtesy of What is Fitness |
Before we get our elbows dirty, let’s preface with the agreement that we are almost never using exclusively one energy pathway. Rather, at any given time, we are using multiple energy pathways/fuel sources in various amounts dictated by the type, duration, and intensity of activity.
We’ll start with short duration high intensity and work out way to long duration, lower intensity.
The phosphagen (a.k.a. ATP-CP) energy system can produce the greatest power outputs, but it is depleted rapidly.
WHAT THE BUNS ARE ATP?
ATP (Adenosine Tri-Phosphate) is the energy currency of life. It is a molecule containing 3 phosphates, and the bond to each of those phosphates releases energy when it broken (when ATP releases energy, a phosphate is released and it becomes Adenosine Di-Phosphate – now containing 2 phosphates).
WHAT ABOUT CP?
CP (Creatine-Phosphate) a.k.a PCr (Phosphacreatine) is another high energy molecule that can rapidly replenish ATP by donating it’s phosphate to ADP.
CP + ADP = ATP + Creatine
There is only enough ATP in the body to fuel a few seconds of activity, or to sprint ~ 15-20 yards. There Is about 3-5 times as much PCr stored in the body, and as such, the ATP-CP system [if running exclusively] could fuel about 10 seconds of activity or sprint just under 100 yards.
Note: the primary logic behind creatine supplementation is in that if we are able to store a greater amount of PCr in the body, then we could maintain maximal efforts for an extra few seconds (or perhaps an extra few pounds or an extra couple reps). Hence, studies have found creatine monohydrate to be useful to performance in short duration activity, resistance training, and power sports, but relatively useless to aerobic/endurance exercise.
