I would say conditioning. I know when I was a bit younger, and in the service personnel would foul up on replacements and we wouldgo frm 10 hr days to working from before the sun comes up, (0300) till sometimes 2200, then be back at 0300 in the morning. Sometimes for months on end. after about a week of dragging tail, you get a second wind and keep going. Didn't matter, troops had to eat, job HAD to get done, and done right...

