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Energy System Training – Part 3 – Anaerobic Athlete V’s Aerobic Athlete

Posted 3rd November 2015 by Josh Schouten

We now know how energy gets into our bodies via the food we eat, we also have an understanding how the anaerobic and the aerobic energy systems utalise ATP stores (see Energy System Training – Part 2).

Energy production (ATP) is both time and intensity related.  For example, sprinting at a very high intensity is only possible for a very short period of time, whereas running at low intensity can be sustained for a much longer period of time.  There is a relationship between exercise intensity and the energy source being utalised. For most sports lasting longer tan 20-40-seconds the aerobic fitness is hugely important in the ability to sustain energy production over the duration of the activity.

The following image, taken from a 1999 study by Parolin et al., shows an accurate image of the time domains and the different energy system usage.  The subjects were asked to complete 3 x 30-second bouts of cycling sprints with 4-minutes recovery between sets.  The A graph below provides a comparison of the first sprint compared to the last sprint in graph B.


As you can see, all three energy systems are working at exactly the same time – at the onset of activity and throughout the 30-seconds.  The contribution of each system depends upon the individual athlete, the effort applied and the rate at which energy is being used.  At any one point in time one of the energy system will be the dominant producer of ATP, as one system reaches its threshold another energy system will take charge of ATP production.

In the above A graph (first sprint) the first 6-seconds of work places a huge demand on the alactic system (ATP-PCr and glycolysis).  The next 11-seconds of work is owned by the lactic system (glycolysis), and finally the aerobic system (oxidative) kicks into play for the remaining 15-seconds.

Graph B (last sprint) shows us a number of interesting comparisons:

– There is a large change in the production of lactic (glycolysis energy system) from the first sprint to the last sprint.

– The total ATP produced is lower than the initial interval (graph A). The result shows that the glycolysis pathway failed to reproduce the same levels of ATP in the third interval, even with a 4-minutes rest between bouts

–  The aerobic energy system is required to contribute higher levels of ATP production much sooner, meaning the athlete’s aerobic capacity was being utalise more in the third interval.

The athlete in question had no choice but to slow down in the repeated intervals because he/she simply could not maintain the total energy demands produced in A.  The aim of the study was to perform maximal efforts bouts, hence the demand on the energy systems was always going to cause this output. If the aim of the study was to produce a consisted energy output across all three intervals the athlete would need to learn how to pace the each repeated effort to conserve energy.

In another study by Noville in 1994, the same results where seen when athletes attempted multiple all out maximal effort repeats of 30-second sprints with 4min rest between.  The rate of energy production changed from one sprint to the next.  As max effort all-out activity are repeated they quickly becomes more and more aerobic, which is why athletes generally slow down with each repeat, unless they learn how to pace and leave some energy in reserve.


At some point in time all energy system will reach their threshold – EST training protocols can be used to improve the threshold times. There are greater margins of improvement in the aerobic system then the anaerobic system.

Its important to remember that there is always a tradeoff between speed, power, strength and endurance.  It makes sense that different athletes are able to produce different amount of power anaerobically versus aerobically. This difference is called the anaerobic power reserve.  Athletes with a large aerobic power are able to maintain a greater average level of speed for a longer period of time than those with large anaerobic power.  The more aerobic energy you can produce at any given point in time, the longer you are going to be able to sustain that particular level of energy production.  Oxygen is free and in abundance, as long as you can keep breathing and working at a sustainable rate your body can maintain it energy demands for an extended period of time.


Both the aerobic and anaerobic systems can be trained and improved to help overall work capacity. This leads to a very important question, “What is your sport and how should you train to improve you performance in that sport?”  You cannot have both ends of continuum, you will never see an athlete become a world champion 100m sprinter and a world champion marathon runner. Each sport has its own energy demands and each coach and athlete needs to understand the demands of the sport and the impact on the energy systems.

The fitness industry has been misinformed that high intensity interval training (HIIT) is the best way to improve overall fitness levels.  This statement holds true over a short period of time (4-6weeks), the body will respond better to HIIT because of the strong stimulus – a high level of stress.   Over a longer period of time this high levels of stress is going to quickly cause fatigue, overtraining and plateaus in improvement. Nobody can handle high levels of physical stress for extended periods of time.  Stress will impact strength, fitness, health and body composition in the long run, never think that you can out train stress.

If you go to the gym every single day and smash yourself into the ground, you are going to see improvements in the short run, but over the long run you will end up hitting a plateau, loosing strength, loosing fitness and possible getting injured. The more intelligent athletes will train at a moderate to low intensity and take rest days to allow their body’s to continually adapt and improve gradually. There will be days when maximal strength and power can be tested, but one would be wise to remember that testing and training are two very different things. We will talk more about competing (testing) and training the energy systems a future post.

Athletes who train at a moderate to low level of stress will see steady improvements over a longer period of time.  Their bodies will adapt to the low to moderate levels of stress and continue to make continuous improvements.  The higher the intensity of the training the longest the rest needs to be between sets and between training sessions (the frequency of training).  Rest is the most forgotten attribute of training and it is by far one of the most important.