[_broody]

It's a lot easier to stay focused on physical jobs, if only because they keep your blood flowing.

In contrast, office employees chug a lot of stimulants every day (coffee) and still manage to spend the afternoon fighting off drowsiness.

[deadfall]

I disagree somewhat. Repetitious physical work can make you lose focus quite easily and that is when most accidents occur. On the contrary, office employees that drink lots of coffee and being drowsy doesn't have to do with work necessarily, but with the their bodies being immune to the caffeine.