Lumbago

Due to my lumbago, I won't be able to attend Koizumi's party.

Sir Oswald Feiling winced as he turned to go home. He had felt a warning twinge of lumbago.

We may imagine an athletics coach with a scientific training researching into the physiology and the psychology of runners. [...] He finds out the effects of fatigue, of alcohol, of tobacco, of lumbago and of depression upon their performances.