Black minus sign above head in crewmanagement?

[Marcus]

Hi all,

I cannot find the documentation in the manual regarding the black minussign appearing above the heads of the crew and their meaning. Now I can see that there "Ausdauer" (yes I prefer playing the game authentically) is darkred and they won't move unless moved by me, but is that all? They don't seem to rest or regain their strengths. Any ideas?
Thnx