Our daily work is a great strain on our energies. We get tired, bored and exhausted by the day’s drudgery. So a whole day’s work makes everybody tired, irrespective of the fact whether it is physical or mental. But most of us do not know why this happens? It is really very interesting to know the reasons.
When we do some work at a faster rate, the muscles of our body do not get as much oxygen as they need. In such a situation, in order to give extra energy to our body, the glycogen stored in our muscles is converted into lactic acid by the process of fermentation. The lactic acid reduces the working capacity of the muscles. This state of our body is called muscle fatigue or exhaustion. The lactic acid acts as a poison for our muscles. So if it is removed from the muscles by the removing process, they can again become fit for working.
Because of the muscular action, some other substances known as fatigue toxins (pollutants) are also made in the body. Blood circulates such acids and toxins through out our body. As a result of this, both our body and brain get tired. Even when we are engaged in some mental work, lactic acid and fatigue toxins are created in the body and we become tired. Scientists during their several experiments once conducted this experiment with a dog. A dog was made to work hard for hours. When it got tired, took rest and finally slept, its blood was transfused into the body of an alert dog. This active dog also got tired and fell asleep. In the same manner they transfused the blood of an active dog into a tired dog’s body and found that dog becoming active all of a sudden.
Fatigue is both a chemical and biological process. It is a defence mechanism, which tells us when to stop working and to take rest. Fatigue cannot be expelled quickly. It is very necessary to provide rest to the cells of our body to remove fatigue. Rest at regular intervals repairs the damaged cells of the body and provide more oxygen to our body. With the arrival of proper quantity of oxygen in the body, the lactic acid is transformed into glycogen and we again start feeling fresh. Little rest also capable of reducing fatigue to some extent. The reduction of glycogen due to fatigue is also fulfilled to some extent by taking food. Thus a tired person feels hungry too with sleepy.