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Updated: Nov 17, 2020

To really understand the origin of FTP and performance you could delve into the metabolic biochemistry of what happens within the body during exercise. Rather than jumping into these more complex details let’s look at it in a very simplistic way. Let’s imagine that our body is a factory. Energy is produced using two production belts. These production belts are your Anaerobic (Glycolysis) system and your Aerobic System. When any movement or exercise starts your body will use carbohydrate/glycogen/glucose and turn it into energy. The anaerobic production belt produces energy through the production of lactate and the aerobic production belt takes this lactate and adds oxygen to produce energy. What happens next depends on the load of intensity of effort. Let’s look at 3 possible loading scenarios as follows:

  1. Low intensity load or easy endurance

  2. High intensity load above threshold

  3. FTP or Steady state threshold efforts 

1. Low intensity load or easy endurance efforts

Carbohydrate is taken into the anaerobic system and a small amount of lactate is produced. At low intensity this lactate enters into the aerobic system where oxygen is added. The aerobic production belt is therefore running at a higher speed or rate than the anaerobic production belt. Since the amount of fuel required cannot be met by the low levels of lactate, fatty acids step in to cover the shortfall. This is what happens during what you will commonly know as base miles, long slow endurance and fat oxidisation. Your body uses a little bit of carbohydrate and more fatty acids to produce energy.

2. High intensity load above FTP

Exercise with a high loading rate results in high levels of lactate production. Because the lactate concentration is high it is not possible for lactate to enter into the aerobic system.

This means that there will be a build up or accumulation of lactate. This is what happens when you sprint or have short maximal efforts.

The anaerobic production belt is operating at a higher speed than the aerobic belt and producing lots of lactate or energy from carbohydrate.