Expected Physiological and Performance Adaptations

The more plus signs, the greater the adaptation.


Training creates all sorts of changes in the body. Resulting in an improvement of the performance capacity. After those changes the body is better able to withstand the stress of the physical exertion.

Increased plasma volume:

The plasma volume of the blood increases. That is a physiological adaptation of the body to endurance training. Blood consists of blood plasma and blood cells. In humans, the ratio is roughly fixed. In humans the blood is composed of 45% of red blood cells and 55% of blood plasma.


The hematocrit is the fraction of red blood cells. In our example, the hematocrit is 45vol%.

Why the plasma volume increases after a period of training? If the plasma volume increases the blood becomes thinner and especially less viscous. As a result, the blood flows more easily through the capillaries. These are very small blood vessels, especially in the muscles. In these capillaries the blood delivers oxygen and nutrients that are necessary for the working muscles. In addition, the blood absorbs CO2 and waste materials which are eventually removed from the body. If the blood is thinner, the exchange of nutrient and waste products in the capillaries will be easier.  In other words, the energy supply to the muscles is made easier if the blood is thinner.

Increased blood volume occurs as a result of endurance training, but also as the result of an altitude training which are very popular among professional cyclists. During a stay above 2500 meters the plasma volume can increase substantially.

The plasma volume decreases after blood transfusions or after EPO treatment. In that case the hematocrit rises.

An increase in plasma volume decreases in hematocrit.

With a decrease in plasma volume increases the hematocrit.

Increased mitochondria:

Mitochondria are tiny energy-producing factories in muscle cells. Training creates more factories that can provide more energy, in a more efficient way.

Improving anaerobic threshold:

After a period of training FTP increases. That means producing of more wattage on the deflection point.

The Cardiac output increases:

HMV = stroke volume x heart rate.
Stroke volume is increased by endurance training.  The sports heart works much more efficiently than the heart of untrained people
Cardiac output at rest is 5 l / min. The stroke volume of the heart of an athlete may be twice as large as that of an untrained person. Cardiac output of sports heart easily reaches 40 l / min.

Increase glycogen stores in the muscles:

The amount of glycogen, the super fuel for the muscles, increases in highly trained endurance athletes. Well-trained endurance athletes make more use of fat burning. They switch at a later moment, at a higher intensity level, on glycogen for energy. Therefore they save their glycogen stores so that they are in the final of the competition in the advantage over their competitors who have consumed at an earlier stage of the race their glycogen stores. The workers in the team who keeps the leader out of the wind consumed their glycogen stores while the leader, at ease in the wheel of his team mate, is only consuming fat. He saves his glycogen for the final of the race.  Wisdom from cycling “eat first the plate of your teammate or your opponent” before embarking on your own plate.

Hypertrophy Slow Twitch fibers:

The slow muscle fibers, type I fibers, become stronger and increase in size. This is important because of that the aerobic capacity increases. The slow muscle fibers use fat as the main energy source (triglycerides). Moreover, the slow muscle fibers break down lactate causing acidification occurs at a later time.

Type IIX fibers transform into Type IIb fibers:

Moreover, by training the rapid X Type II fibers transform into the super fast Type IIb fibers.



Increase of VO2 max:

Also, the increase of VO2 max is a result of training. If the FTP is known, the VO 2 max can be calculated easily. The maximum FTP that can be achieved is  6.4 Watt / kg, this  corresponds to a VO2 max of more than 88 ml / kg / min. According to the formula ADV = 0.072 x VO2 max.

These values are only achieved by the world champions. VO2 max through training can improve up to 30%. Most athletes never reach a VO2 max of 88. Not even after years of training because their starting position is too low. That baseline is in fact genetically determined.

Increased energy phosphates ATP and CP.
Hypertrophy of the Fast Twitch muscle fibers.
Increased neuromuscular strength:
The explosiveness increases.