I fell asleep for a couple of hours, and I am a little stiff and sore, now. But it's mostly in my legs, buttocks, upper back, and shoulders, with just a little in my lower back, which means, I think, that I demonstrated good posture and ergonomics throughout the day. Yay! Of course, tomorrow is another day... I could be in pain tomorrow, but I hope not...we have 48 more shelves to go.