How does our body burn fuels ? Ever wondered!!?

Adenosine Triphosphate(ATP) is the only fuel your body can use. The cell breaks down ATP and generates energy that can be used directly. ATP is the fuel of life.  There are three major energy pathways by which ATP is produced - our body chooses the most efficient energy pathways depending on the specificity of the requirement.

1. Oxidative or Aerobic Energy System 

2. Anaerobic Energy System  or Anaerobic Lactic

3. Immediate Energy System or Anaerobic Alactic

A small analogy to understand this concept. Oxidative Energy system is like your NEFT transfer, you can transact huge amounts of money but it is a long process and comparatively slower than the other means of money transfer - your body chooses this for all your slow and steady activities.  Anaerobic energy system is like the UPI transfer, faster but there is a lot of limitations in the number of transaction or amount of money - Your body chooses this pathway when the energy required is highly intense for few 10 seconds. Immediate energy pathway is like the small amount of cash that you can fit in your pocket and you will only use it in emergencies - Your body will choose this pathway when the energy requirement is very intense and urgent and for just a few seconds.

Oxidative Energy System or Aerobic Energy System:

For example in a full marathon, a runner, for most part, runs in the aerobic zone. Since the duration of this activity spans for several hours - This is a high volume transaction and hence  comparing this to a NEFT fund transfer.  In this pathway, your body breaks down Carbohydrates and Fat into Glucose and then creates ATP - This is why your pre run meal is very important for your long runs.  This requires steady supply of oxygen for every cell - Endurance athletes tend to have a higher VO2 max. This ATP is produced in the mitochondria of the cells. An experienced runner will have an increased amount mitochondrial density thus efficiently producing slow and steady energy for several hours without any deficit.  Remember, back in the 8th grade biology class, the mitochondria is called as the power houses of a living cell. This is why!

Immediate Energy System or Anaerobic Alactic:

Consider a case of an olympic weightlifter, he has to lift a heavy loaded barbell from the floor to over the head in one swift movement called the snatch. Usually these lifts are very fast and intense, it takes only few secs but it requires sudden burst of energy with zero delay. Our body stores ATP in its readily usable form for such immediate high intense requirement. This is the cash you keep in your pocket, there is no hassle, no internet failure, just direct cash transaction. But the only drawback is the small amount of money you can fit into your small pocket.

Once the athlete lifts the weight, his Stored ATP will be exhausted.  The athlete rests and recovers for few mins and in the meantime, the ATP concentration is again increased by your body and the athlete goes on to lift the weight one more time. 

Creatine Phosphate (CP) is another substance available in the cell that can produce ATP. These ATP/CP can only fuel for a very short duration say 2-3 sec.  but a rapid explosive energy.    Any competitive athlete generally supplements Creatine Monohydrate in their daily diet to increase the stored ATP/CP concentration - This will largely improve their anaerobic performance. This is like adding few more pockets to your shirt to hold that extra bit of money. 

Anaerobic Energy System  or Anaerobic Lactic:

Take the example of an 100m sprinter. A seasoned athlete takes around 10-12 secs to sprint a 100m distance.  The readily available ATP can only produce the energy for the first 10-15 meters and once that is exhausted, the body switches to the next explosive energy pathway - Non-oxidative or Anaerobic. This energy pathway can fuel highly intense activity for a slightly increased duration. This process doesn’t require oxygen. This breaks down locally available Glucose and Glycogen to create ATP.  The Byproduct of this process creates hydrogen ions and lactic acid buildup in the muscles - creating muscle tiredness and fatigue - which is the limitation of this energy pathway. With the right training, the athletes can increase their tolerance to this fatigue to some extent - lactate threshold. This energy system can only fuel the body for a 10-30 secs but fairly quickly, thus comparing this to an UPI transaction. Fast, but with daily transaction limits.

Let's assume an inexperienced runner sprinting a 100m race. You can see him huffing and puffing at the end of the race. If the Anaerobic energy system doesn't require oxygen, why does he fall short of breath? It's because to cross the 100m distance, an inexperienced runner would have exhausted both the immediate and the anaerobic energy pathways and he has already switched to the aerobic energy system at the end of the race and goes out of breath.  

In papers, it is said that your body is switching from one energy pathway to an other energy pathway.  But, in ideal conditions your body may run on all these energy system at one point of time but in different proportions. 

Article by Elvis Yesurajah.