The energy systems

Where should you start to create your training program? A lot of information is available via the internet. Terms like Energy Systems, Lactate Threshold, Functional Threshold Power, Anaerobic Threshold and Ventilatory Threshold Power are thrown at you like you’re a scientist yourself. What’s the difference between those terms and which threshold is the most important?

Well that’s easy: all of them. Why? Although all terms have other definitions, they essentially tell you the same thing about your fitness! First, let’s have a look at some physiology.

Energy systems

In order to have a clear understanding of the terms mentioned previously, we first have to go through some basics. In order to meet the energy requirements of an exercise, ATP (the human “energy carrier” is required. In order to produce ATP, the body uses different energy systems that are cooperating to provide the required energy:

1. The phosphagen system
2. The anaerobic system
3. The aerobic system

These systems work in parallel with each other, meaning that there is not a simple on/off switch for each system. However, the contribution of each system differs based on the demands of a task or exercise.

The phosphagen system

The phosphagen system is the immediate energy system. It will provide you with the energy that is required during short, high-power efforts that last about 10 seconds, when the energy demands are bigger than that the anaerobic and aerobic systems can provide. Cyclists may use these short-term power bursts to get a quick start or gap with the opponents or to squeeze out the last sprint. The phosphagen system consists of two parts itself: free ATP molecules and PCr molecules. When one ATP molecule is used to provide energy, an ADP-molecule remains (from ‘Tri-‘ to ‘Di-‘). In order to recreate an ATP-molecule very fast, the PCr-molecule will ‘donate’ its Phosphate-ion (“P”) to the ADP-molecule. However, both ATP- and PCr- levels, run out very quickly. Therefore, other systems are required.

The aerobic system (“With Oxygen”)

The aerobic system is the major and preferred energy system of the body. It utilizes oxygen to produce ATP out of fat and carbohydrates (and to a lesser extent proteins). And it does so without major waste products. The only waste products from the aerobic system are CO2, which will be removed from the body by respiration, and water! The aerobic system essentially provides you with the energy to go all day. Doing so, it may use a fuel-mixture of different resources (fat, carbohydrates and protein) based on the energy demand and the fuel availability.

The more intense and powerful the exercise, the more carbohydrates will be utilized. However, the aerobic energy system requires some time to really get the engine going and doesn’t provide energy that fast. Therefore, this system is not the preferred system for fast, high-power efforts. The upper limit of the aerobic energy production rate (reflected in VO2max) is mainly set by the cardiovascular fitness.

The Anaerobic system (“Without Oxygen”)

The anaerobic system, or glycolytic system, is the system we all know very well. You are at the point that you are no longer able to produce the required energy with the aerobic system solely. In other words: you’ll need additional resources in order to keep up with the pace. This is where the anaerobic system will contribute to the total energy production (yes, also the Phosphagen System operates anaerobically, but is defined as a separate energy system due to it’s really fast and short-term capabilities).

The anaerobic system provides energy for these high-power and fast efforts. However, this energy comes with a high cost itself. The waste products from the anaerobic system are more hurtful than those of the aerobic system. Lactate and hydrogen-ions will be produced. At first, this won’t be a problem. The body is able to process lactate and other waste products quite well, at a steady rate.

Next: The Lactate Threshold

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