Generally while climbing up the stairs of a building, a person gets more easily exhausted, than while coming down. To lift heavy articles, greater effort is required. It is harder to walk uphill than downhill. Have you ever wondered why?
We know that our earth attracts everything towards its centre. This is known as the force of gravity of the earth. It is the force of gravity that holds us on the surface of earth. When we move away from the earth’s surface, we have to do work to overcome the force of gravity.
So while going uphill, our muscles have to do more work to lift the weight of our body against the gravity of the earth. For this the heart has to pump more blood to the cells. As a result, our lungs have to do more work to pump out the carbon dioxide from the heart, and to replace it with oxygen. Hence for a steep climb we breathe more quickly.
If we climb a mountain by two different paths — one more steep, and the other less — we would feel greater fatigue in the case of the steeper one.
In comparison to the energy required for walking on a horizontal plane, the total value of the extra energy needed for climbing is the weight of the body multiplied by the total height to be climbed.
When we walk down a hill, very little energy is required because the body is carried down the slope due to the earth’s gravitational pull. This is why our muscles do less work, and we do not feel tired while walking down a hill.