If you check the ldwlog.txt in the VV directory, you'll find it goes down because they've been injured - usually at the research table or building. Taking them to the bin DOES work, but to see an increase on the bar, you have to take them a number of times. I don't like leaving them working when the bar is down 2 notches, cos if they get injured again, it drops way further down... my theory is that's how they eventually become weakened even though there's plenty of food - they keep getting re-injured before they've had a chance to recover. Could be a reason to suggest ldw builds in sick leave into the next game