"Spinning like a squirrel in a wheel" is a figurative expression that applies mainly to situations when a person is very busy with various things. However, it has a completely literal meaning.
The real basis of expression
The fact is that breeders of various rodents, and first of all, squirrels, quite often use a peculiar design for them in the form of a wheel made of wire. The animal is placed inside the wheel and, moving forward, rotates the wheel around its axis with the weight of its body, which necessitates further movement in an attempt to climb onto the upper part of the structure. Therefore, in such a wheel the animal can run for a long time and, as a rule, interrupts its run only when it is very tired. By this moment, it acquires a typical tired appearance of a creature after prolonged physical exertion, which became the basis for the expression "spin like a squirrel in a wheel."
