In the work of a waggon-builder or coach-maker, if a man made a whole wheel, the shaving of spokes would come in its turn with other kinds of work that would call the workman into sundry postures, with sundry muscles in action ; whereas, when by a more exact division of labour, one man is confined only to the shaving of spokes, he may have a daily onholding pressure on the stomach that may soon affect his health.
Source: wiktionary