In Pushing a wall no work is being done. Then what is the reason behind tiredness? Explain in terms of physics...

Tiredness is a function of energy dissipation, which may occur through various forms. Only one form of this is work. In the case of pushing a wall we are constantly supplying energy which makes us tired. It would also happen if you just sit on a chair for the whole day. The answer to this energy flow lies in one of the most simple experiments of stretching a rubber-band, of course without breaking it. Let us see this phenomenon much more closely. Take a normal rubber-band and stretch it with your fingers. Does it move anywhere? The answer is NO. It simply gets elongated. Now, if you have pulled only slightly, on releasing your fingers, it returns to its original shape. We call it elastic change of shape [formally called as elastic deformation]. And the energy associated with this is called elastic energy. If you had pulled a bit more, it would be a bit more elongated than what it was before. We call this plastic change in shape [deformation]. [Note:- There are further kinds of deformation but currently we shall restrict ourselves to these.] But has it moved from its original position? NO. So, if you were to hold a rubber-band, in stretched position for the whole day what you are doing is providing this elastic energy to the rubber-band. This was elastic energy in tension. Let us see an example of elastic energy in compression. Take a simple eraser in your hand and press it between your fingers. Now it is compressional elastic energy, which you are continuously supplying to it. Let us come to our wall pushing experiment. Here there are many erasers and rubber-bands that are getting compressed and pulled away. 1 The wall is getting compressed. Even if you can't see, the molecules in the wall are deformed. 2 Your own skin on the palms. 3 Your finger bones. Yes they too are elastic due to their porosity [of course within limits] 4 If you are not wearing your shoes and the skin of feet against the floor. 5 The irregularities of floor surface which we see as friction. 6 Countless tiny ligaments and muscles which get pulled. These are based on physics. More than this there are many biological reasons as well, in terms of ATP [Adenosine Triphosphate- the chemical for intracellular energy transfer] metabolism, which causes change in blood pressure, thus again leading to consumption of energy. read less