"A stress fracture is a crack that does not go completely through the bone. Initially called march fractures, they were first noted in the 19th century in Prussian soldiers who marched too far or too often. The injury has two main causes: too much repetitive stress on a bone and/or weakness of the bone, which can result from a number of different factors. If the repeated strain is greater than the strength of the bone, then it will fracture."
— Finally my spiritual link to Prussian soldiers makes sense.