Sprint, walk, endurance run or strength training – your body constantly needs energy. But how exactly does it supply it? In this blog you'll learn in an easy-to-understand way how energy supply works, which systems are involved and what the whole thing has to do with a campfire.
What does energy supply actually mean?
Energy supply describes the processes by which your body delivers the "fuel" that muscles and organs need for their work. Different pathways come into play here – and that simultaneously. So one system isn't switched off and another switched on; rather, the various pathways run parallel to one another. Depending on the load, however, their shares change fluidly.
👉 The most important "raw materials" for these processes are sugar (glucose), fat (fatty acids) and creatine phosphate. They come on the one hand from your nutrition – that is, from carbohydrates, fats and proteins that you consume throughout the day. On the other hand, your body can also produce, convert or store some of these substances itself – for example glucose in the form of glycogen in the liver and muscles, or creatine phosphate directly in the muscle cell. Via the blood, these energy carriers reach the cells that currently need energy – particularly often the muscle cells during training. That's where the actual energy supply then takes place.
Aerobic energy supply – endurance through oxygen
When you jog gently, go for a walk or do the housework, the energy supply runs predominantly aerobically – that is, with the involvement of oxygen. In the mitochondria, the so-called "power plants" of your cells, sugar and fat are broken down into water and carbon dioxide with oxygen consumption. This produces a lot of energy, with which the universal energy carrier ATP (adenosine triphosphate) is formed.
The whole thing does take a little longer, but also lasts much longer and is dominant during longer activities at low intensity.
Anaerobic energy supply – fast, but limited
When you suddenly set off at high speed or train intensively, your body has to supply energy immediately – even if there isn't yet enough oxygen available. Now the anaerobic energy supply kicks in more intensively. This runs directly inside the cell (cell plasma) and uses either creatine phosphate or glucose to produce ATP – but with a considerably shorter burn time.
The disadvantage? The reserves are limited, and metabolic products form that can quickly restrict performance.
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Practical example: energy supply like a campfire
Imagine you want to rekindle an almost extinguished fire. Different fuels have different effects – just like the different pathways of energy supply in your body:
- 🔹 Creatine phosphate (anaerobic – without oxygen) is like a fire accelerant: very fast, but only for a few seconds. Your body uses this, for example, during a short, explosive 100-metre sprint.
- 🔹 Glucose (anaerobic – without oxygen) is like newspaper: it burns a little longer, but is quickly exhausted. This comes into play during medium loads such as an 800-metre run.
- 🔹 Glucose (aerobic – with oxygen) acts like small kindling: it needs a bit more time, but is already quite efficient and lasts a few minutes. A typical example would be a 3.5-kilometre run at a moderate pace.
- 🔹 Fat (aerobic – with oxygen) corresponds to a large piece of wood: it takes the longest to ignite, but in return lasts really long. Your body uses this pathway during longer endurance efforts such as a marathon.
And importantly: even if the "fire accelerant system" is active at the start, smaller and larger pieces of wood are already being added at the same time – just as your body uses all systems from the very beginning, only to varying degrees.
Training relevance: what does this mean for your workout?
Depending on what you want to train, you should specifically target different pathways of energy supply:
- Anaerobic-alactic loads (creatine phosphate system): For explosive strength and power – e.g. short sprints, jumps or heavy strength training with few repetitions. Train at very high intensity and with long breaks (e.g. 1–2 reps with at least 2–3 minutes of rest), so that the creatine phosphate can regenerate.
- Anaerobic-lactic loads (glucose without oxygen): For speed endurance, interval training or longer loads of 30 to 120 seconds. Typical examples are 200–800-metre runs, HIIT sessions or also strength training in the hypertrophy range with medium load and a high number of repetitions and/or incomplete breaks. The body learns to deal with lactate and to improve its performance.
- Aerobic loads (fat and glucose burning with oxygen): For basic endurance, fat metabolism and recovery. Train at medium to low intensity over a longer period – ideal are easy endurance runs, longer cycling or walking. This improves mitochondrial performance and energy generation from fat.
A balanced training plan takes all energy systems into account – tailored to your goal, your performance level and your recovery capacity.
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Conclusion: everything works together – but not equally strongly
The different systems of energy supply complement each other optimally. Depending on the load, sometimes one system, sometimes the other takes the leading role. But: all are always active to a certain extent. Your body is a real multi-tool when it comes to energy – efficient, flexible and adaptable.
👉 That's why in training it makes sense to specifically challenge different energy systems – for holistic performance development, more endurance, more explosiveness and a better recovery capacity.
👉 Important to note: Training in the aerobic range can too – correctly dosed – improve your performance in the anaerobic range, and vice versa. The energy systems influence one another, which is why varied training is the most effective in the long term.
