[I have seen] workers in whom certain morbid affections gradually arise from some particular posture of the limbs or unnatural movements of the body called for while they work. Such are the workers who all day stand or sit, stoop or are bent double, who run or ride or exercise their bodies in all sorts of [excess] ways. ... the harvest of diseases reaped by certain workers ... [from] irregular motions in unnatural postures of the body.