Fatigue is our enemy or friend?

It would seem that fatigue is a bad phenomenon, the enemy at all one hundred percent. In fact, we will not hurry with this assessment. Simple answer here can not be.
Of course, setting a limit to the athlete's achievements, reducing employment opportunities and the well-being of the worker, fatigue is a phenomenon harmful and undesirable. Here it is, no doubt, must be qualified as our enemy.
The reader may even legitimate question. It turns out that the appearance of the higher brain centres in the course of evolution led to the decrease of efficiency, i.e. reduced capacity of the organism, caused him harm. Direct experiments at first glance confirm this. Irritating electric shock sensitive nerve frogs, cause reflex through the spinal cord reduced its feet. After a certain time comes fatigue. If you remove the frog brain, fatigue in such experiments is later. The presence of the brain, it would seem, is clearly reduces efficiency. Note that if this were so, the animals still would not be a loser. Quantitative performance decrease was compensated with the surplus due to higher quality, greater efficiency, controlled by the brain. Remember the words of Engels that the eagle sees much further than the man, but the human eye can see things much more than an eagle eye. However, quantitative performance, in fact, is not reduced. The same experiments show that beheaded frogs fatigue occurs later, but recovery after it goes on much longer. In more normal frog rapid exhaustion more than offset a quick rest, and for a number of repeated periods of activity total work will be considerably greater. Hence, appearance during the evolution of animals of higher functions of the brain that are tired quickly, harm to no avail.
Everything we have talked concerned harmful, objectionable hand fatigue. It was, so to speak only about the degree of hazard. Along with harm, however, fatigue and brings undeniable benefits, which acts in two plans.
First, fatigue plays a protective role, protecting the Executive bodies from excessive waste of resources, depletion. Fatigue higher brain centres - it is like a safety valve. The above experiments with normal and beheaded frog, and a number of other facts proved by the protective role of fatigue. Of course, this reaction may be not quite perfect.
In addition to the inhibition of the activity of the Executive apparatus of the refusal of the conductor leads to discoordination, inconsistent job functions. In these circumstances, the continuation of the work despite the fatigue can cause failure, fatigue, i.e. disturbance of the normal state of the organism. However, with all possible imperfection of this reaction in its protective biological role is not in doubt.
Secondly, exhaustion is a prerequisite for increasing the efficiency in the course of the exercises, training. At the end of last century was installed interesting biological law - the so-called principle of supercompensation, or sverhvosstanovlenie. After great biological spending recovery is abundant and resources at a certain moment, perechislyayut" initial level. Again a big load executed in this period, again gives supercompensation etc., It is based on gradual increase of the functional abilities of the body during exercise. Of course, excessive loads can give stress and breakdown recovery processes, but to a certain limit the intensity and volume of work, and hence increased the degree of fatigue works in our favor.
Therefore, we should always be considered an important victory in the biological treatment of fatigue. It is not only protective, protective reaction, but, in addition, provides the subsequent growth of health. We see here a striking example of the internal contradictions in the phenomena of living nature, once again emphasizing the need dialectical understanding. Fatigue is for us and the enemy, and the other at the same time.