I try to get up and walk around for a few minutes every hour or two.
One of my most talented colleagues a long time ago used to spend an hour a day walking around talking to people in other offices. I was surprised it was not discouraged by management. But they recognized his talent and realized it helped him get more done; he was incredibly productive. He is now a Professor at MIT, so I think it served him well.
"Working hard" is over-rated. What counts is results. And the formula for getting results is a lot more complicated than just working longer hours.