How Understanding Energy Systems Can Improve Runners Training Strategies

You've likely been told to think big. And while with most things, I believe thinking big is valuable, I've realized that sometimes we need to think small.

When it comes to training, I'm a big proponent of simplifying and strategizing rather than shooting in the dark. If you know your destinations, you can better understand which map to use –– most of the time. But sometimes, it's not that simple. Yes, you know you want to go downtown to the new coffee shop, but should you take the bus, walk, or bike?

Within simplicity, there is a place for thinking small, and since the cell is the smallest unit of life, we may as well start there. My goal here is to show you the value of energy systems and how to use that understanding to leverage optimal adaptations in your training. As humans, we generate energy via three energy systems: phosphagen (ATP-CP), glycolytic, oxidative. As a runner, understanding these energy systems will allow you to simplify your training strategy.

First, you do not control which energy systems you are using consciously; all of this is subconscious. And if you were to take anything from this article, remember that energy systems are best correlated with time and intensity. They don't know distance sets reps or otherwise. This fact is vital in understanding how the systems work and how you can work these systems.

ATP production via the phosphagen system

The phosphagen energy system is the initial energy system used during short, intense activities. During such activities, your body relies on ATP (adenosine triphosphate) as an immediate energy source so that you can generate large amounts of power in your musculoskeletal system. ATP is often referred to as energy currency for cells. Think of them like energy banks. 

The phosphagen energy system is our body's fastest way to synthesize this ATP. During exercise, phosphocreatine links with ADP, adenosine diphosphate to create ATP, a.k.a. energy. So, remember how earlier I said energy systems are best related to time and intensity? Well, the phosphagen energy system is used during the first 10 to 30 seconds of intense exercise. In terms of running, think sprinter.

The glycolic energy system, also known as the anaerobic energy system, uses carbohydrates to produce ATP. Our bodies tap into this energy system once the phosphagen energy system has run its course. 

Carbohydrates provide our bodies with glucose. These carbs are broken down via glycolysis. This glucose makes it through the Kreb's cycle and oxidative phosphorylation to generate ATP. Our bodies rely on this energy system during intense bouts of activities that last from 30 seconds to 3 minutes.

Know that the phosphagen system and the glycolytic systems do not require oxygen. Anaerobic quite literally means without oxygen, and both of these energy systems are referred to as anaerobic.

Unlike the other two, the oxidative system is aerobic, which requires oxygen to produce energy. Unlike the glycolytic system, the oxidative system relies on fats and proteins to create energy. This is the primary energy system used when running a 5K or marathon. 

Note that the descriptions I've laid out are an oversimplification; your body is constantly tapping into all three energy systems. Considering the relationship between time and each energy system is a valuable tool when designing your training strategy. 

First Consideration: Running

This first consideration is the most obvious of the two. Runners of all races often make the mistake of only training within the constraints of their competitive distance. So the question becomes, how might a distance runner benefit from training as a sprinter, and vice versa? Remember, energy systems are dependent upon time and intensity. Like anything, these energy systems will adapt and become more efficient with training. Call this metabolic adaptation.

With speed work, distance runners, for example, will be able to run at a higher intensity, longer. Training within the constraints of the anaerobic energy system will improve your bodies ability to store phosphocreatine and carbohydrates so that it is readily available for ATP generation. Not only will distance runners benefit from speed work but sprinters from distance work. Distance/endurance work will improve aerobic capacity, lactate removal, temperature regulation, and aerobic enzyme production (responsible for producing ATP). No matter your race, or pace, your training should be diverse if you want to maximize your performance.

Second Consideration: Resistance Training

This second consideration is far more profound than the first. Most don't consider time and intensity in resistance training under the umbrella of energy systems. Most think sets and reps. While those forms of overload and structure lend will to muscular adaptation, it's important to remember that your body doesn't know sets and reps; it knows intensity and time under tension ("energy systems are best correlated with time and intensity"). 

In a resistance training session, a sprinter would want to bias the phosphagen and glycolytic energy systems. They could achieve this by working within a 30-second window rather than contemplating rep schemes. A sprinter can be specific within these constraints if they understand what adaptations they'd like to train. Don't forget that intensity also plays a crucial role in leveraging any particular energy system. You probably won't have much success, or any at all, training the anaerobic energy system if the weights you lift are remarkably sub-maximal (easy). On the other hand, a distance runner can bias the aerobic energy system by keeping their lifting "reps" well beyond 30-seconds, preferably beyond 90-seconds.

I urge you to allow these new learnings to inform your understanding of training and your training strategies. Energy is where it all starts; without energy, our cells, organs, muscle tissue could not survive. Sometimes we have to strategize small to demand significant results.