Riding a bicycle doesn’t save energy, so why is it less labor-intensive than walking?

Is it more labor-saving to walk or ride a bicycle? Of course it is to ride a bicycle, otherwise bicycles would have no value in existence.

Although a bicycle is a simple means of transportation and its structure is not complicated, it involves many principles of physics. We all know that levers can be divided into effort-saving levers and effort-consuming levers, and bicycles are typical effort-consuming levers. However, don't be confused by the name "effort-consuming lever". An effort-consuming lever does not mean it is really effort-consuming. The so-called effort-consuming lever means that under the condition of lever balance, the power is greater than the resistance, and the power arm is smaller than the resistance arm. Because the power multiplied by the power arm is equal to the resistance multiplied by the resistance arm, the effort-consuming lever appears to be labor-intensive, but actually saves distance, which ultimately saves effort. Specifically speaking of the problem of bicycles, the driving wheel is larger than the driven wheel, that is, the chainring on the pedal is larger than the flywheel on the rear wheel, so as to achieve the speed increase.

With the help of the bicycle, a labor-intensive lever, we can travel a farther distance in the same amount of time, thus saving effort. However, the effort-saving benefits of a bicycle are not limited to this. Even if we ignore the distance and only consider the time, riding a bike is still less labor-intensive than walking. In other words, walking for an hour is more tiring than riding a bike for an hour in the same hour. Why is this?

This is actually a rather puzzling thing, because any machine cannot "save power", it can only waste more power, and bicycles are no exception. Since bicycles cannot save power, then in the same amount of time, riding a bicycle cannot save more power than walking. Obviously, the theoretical results do not match the actual situation, which shows that there are some problems that we have overlooked.

From a macro perspective, walking does require less energy than riding a bike, but the human body itself is also a machine that does work in places we cannot see.

Work is the process of converting energy from one form to another, which requires the object to move in the direction of the force. From the definition of work, carrying a bucket of water to the second floor is work, while carrying a bucket of water for 2 kilometers is no work, because the force is upward when lifting the bucket, so the former moves a distance in the direction of the force, while the latter does not. This conclusion is not wrong, but it is also based on a macroscopic perspective. In fact, although no work is done when carrying a bucket of water, it is still very tiring. Why? Because on the surface we are not doing work, but the muscles inside our body are always doing work.

In order to lift the bucket, the thin filaments in the human arm are constantly sliding on the thick filaments, and this sliding is driven by the "cross bridge" on the thin filaments, so on the surface the person is not doing work, but in fact the "cross bridge" in the human body is always doing work.

People need to rely on the muscles of the body to maintain any posture. Different postures mobilize different muscles. We stand when walking, but sit when riding a bicycle. Obviously, standing requires more muscles than sitting, so standing is more strenuous than sitting, and walking is naturally more strenuous than riding a bicycle. In addition to the extra energy wasted by posture, we also spend extra energy to fight against gravity when walking. When riding on a straight road, we do not need to fight against gravity because the bicycle is always moving forward, not in the opposite direction of gravity, that is, moving upward, but walking is different.

When a person stands upright with his legs together, his vertical height is the highest and his center of gravity is also the highest.

When a person moves forward with his legs apart, his vertical height will decrease, so his center of gravity will also decrease. Walking is essentially the process of a person moving from legs together to legs apart, and then to legs together. During this process, the center of gravity of the human body will continue to move up and down. When the center of gravity moves from bottom to top, people must do work to overcome gravity, which requires extra effort. This is one of the reasons why walking is more strenuous than riding a bicycle. Is that the end? Of course not. There is a third reason why walking is more strenuous than riding a bicycle.

You can move at a constant speed by riding a bicycle, but you can't walk.

From a macroscopic perspective, walking can indeed be a uniform motion, but if we break down the walking process, it will be different. Every step we take will experience a change in speed. When our foot just lands on the ground and pushes down, the speed is the fastest. After that, the speed will decrease until the other foot lands on the ground and pushes down, and it will accelerate again. So on the surface, walking seems to be a uniform motion, but in fact it is an accelerated motion, and a repeated accelerated motion. We all know that it takes more energy to accelerate an object, so walking is naturally more laborious. Now we understand that although riding a bicycle does not save energy, walking requires a lot of extra energy on other things, so it seems more laborious.

For more information, please follow the official account: sunmonarch