Use it or loose it

We all know that if an athlete does not train for serval weeks, his capacity of performing will decrease very, very fast. But this principle of use / disuse can be observed in all physiologic and metabolic functions in the body. If we talk about muscle strength, endurance, mobility or systems like the immune defense and the ability to recover from injuries. The body adapts very fast and very, very well to exposure. Thereby training, in general, is enabled. It is indeed incredible what the human body is able to handle and how it reacts on stimuli. 

However, this fascinating ability in our body also works the other way round and it suddenly appears less fascinating. A fact that many of us forget about: If our body is not trained, not stimulated in any way, it looses its function in high extends. If we take breathing as an example we can consider it like this: Imagine you are a person who generally breathes rather superficially. You do not do any sports or any other activities where your breathing system gets provoked as it has to allocate more oxygen. Your lungs may get used to limit its use of all the lungs' capacities. The part of the lungs that are not used anymore will be less and less supplied with blood because the brain thinks: Well, if you do not use it I will not do any effort to keep the function on this "high" level. The body more and more decreases the amount of oxygen that can be provided by the lungs. This has not only an impact on endurance, brain function, etc. but it also makes the body more vulnerable to infection. Bacteria, for example, find a nice spot to settle down in the unused parts of the lungs. Because the circulation in 'disregarded' parts is decreased the defense system can not work properly. Bacteria have the best possibilities to proliferate. The best condition is set for infections, chronicle lung disease, etc. Now you are at a point where you need to make a much greater effort to get back to normal functions again, to recover from disease, to prevent worsening of the health state or to get back to shape. 

So why not maintaining the body's function on an appropriate level directly?

This is just a very brief example of the idea how our body works. But this idea can be transferred to pretty much all functions in the body. It is not only about loosing fitness when you stop training, it is about disregarding all the incredible functions of the human body when just bumming around. Therefore: USE IT OR LOOSE IT!

For your information: Fitness can be expressed in a lot of different ways. If there's good equipment available there is the VO2max* or the lactacte threshold**. For the practical use, measuring the heart rate and the performance within a specific time frame are already very accurate next to qualitative signals like breathing and the quality of performance (coordination). Endurance capacity depends not only on the cardiovascular capacity (heart and artery function), but also on the cardiopulmonary capacity (lungs) and the presence of specific muscle fiber types within the activated muscles. If we train our physiologic and metabolic capacities properly our body adapts very well and we observe an improvement in VO2max or the lactate threshold. 

*VO2max (maximal oxygen uptake): It represents the maximal amount of oxygen a body is able to use during incremental exercise. It therefore reflects the individual's fitness (maximal aerobic capacity).

**lactate threshold (LT) or anaerob threshold (AT): In all-out exercises the body accumulates lactate at the same time as it removes it from the blood (steady state). Hence, there is a balance of lactate production generated by activity and lactate removal, which reflects mainly the aerobic energy system. At a certain point or in too strenuous exercise the lactate can not be removed as fast as it is produced by the energy supply systems. The lactate threshold is reached and it starts to accumulate in the blood. The anaerob energy system provides  the main part of energy needed The better trained an individual is, the higher the lactate threshold  is - the more intensive exercise can be performed for a longer time without accumulating lactate.