When you walk,run,skate,and swim, the muscles of the human body work like car engines. The faster the car is running, the higher the horse power of the engine.
The same is true when a person exercises. Excellent athletes in the Olympic Games can produce very high muscle power.
The purpose of their practice is to obtain high skills and increase the muscle power production.
When the running distance becomes long, speed goes down.
The sprinter runs 100 meters in 10 seconds. In the 200 meter race the distance is twice as long but the time is a little less than 20 seconds. However, the 400 meter running takes longer than 40 seconds, four times 10. In the 1500 meter race the speed decreases even more. If the speed is proportional to the muscle power, the longer the distance becomes, the less power is exerted.(Figure 2)
The same thing happens with the speed skating and the swimming.
Let's look at the graph and compare the time records and the distance to go.
The exercise time becomes longer as the distance gets longer.
The power of the muscle decreases when the exercise time becomes long. This is the big difference between the car engine and the animal engin, the muscle. The car at 100km an hour can keep running at the same speed until it loses gasoline or breaks down. However, animal muscles do not work that way.
The longer the exercuse time becomes, the less muscle power human can produce.
The muscles working as the engine of the body use the fuel called the ATP.
There is only a little ATP in muscles that it runs out in ten seconds when we exercise with maximal effort. The longer exercise needs a different energy source. It is called glycogen. ATP is made from glycogen, but at the same time lactic acid is produced. When lactic acid increases in muscle, the muscle cannot make power any more. Even if we try to do push-up many times, we gradually lose power and cannot repeat any more. Increased lactic acid in the arm muscle is the reason of fatigue.
