A manual meat grinder [0] is operated by running a hand crank that moves in a circular motion. The implication is that after two years of having done only this one job, the motion is instilled in the hand such that they can now draw perfect circles. The Soviet army was infamous for both its cruelty and the pointless repetitive errands the conscripts would have to do.

[0] https://en.wikipedia.org/wiki/Meat_grinder