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LIMIT OF HUMAN POWER
Human muscles are like car engines
Walking, running, skating, swimming need muscles working like a car engine. With the higher engine power, the car runs the faster. The same thing happens with the human body. Good athletes you see in the Olympic Games have great muscle power. They have trained to have greater muscle capacity as well as high skills.
Car engine and Human muscle
Sprinters can travel 100 meters in 10 seconds. They take less than 20 seconds in 200meters. However 400 meter running takes them more than 40 seconds. In 1500 meters they run even slower. The longer the distance is, the slower they can run. Suppose the running velocity is proportional to the muscle power, the long distance seems to reduce the muscle power.
The same thing happens with speed skating or swimming. Compare the distance and the velocity in speed skating.
Relation between duration and speed decrease in running
Relation between duration speed decrease in skating
How is muscle different from the car engine?
The long distance takes long time. The muscle power decreases with a long exercise. Our muscles are actually different from the car engine at this point. The cars running at 100 km/h can keep traveling at the same speed until the fuel tank becomes empty. But our muscles do not work like that. When the exercise is long, the muscle power becomes less
Fuel for our muscles
Our muscles use fuel like car engines. Muscle fuel is called ATP. However the ATP exists so little in our muscles that 10 seconds of exhausting exercise spends almost all the ATP. Another energy resource called Glycogen is then used to produce new ATP. While Glycogen is making ATP, lactic acid is emitted into the muscles. Lactic acid controls a muscular movement and limits the muscle power production. After doing a push-up many times, you can not keep pushing up any more even if you try very hard. You got lactic acid in your muscles.
Three types of muscle energy resources
Use of oxygen, non-use of oxygen
Breathing in the nose and the mouth we can take oxygen into our body. The oxygen can change the lactic acid into carbon dioxide and water. With a lot of oxygen little lactic acid is emitted into the muscles and we can keep exercising for a long time. However the oxygen process does not produce much energy or power. The muscle power produced by oxygen process is called "aerobic power". The power compensating with lactic acid without oxygen is called anaerobic power.
Duration of exercise and type of muscle power resources