[mironathetin]

"The solution is to get up and move around often, i.e. every ~20 minutes or so."

I agree. One method to force you to walk twice an hour is drinking a lot of water. This will keep your brain fit, you will be much less tired in the evening, when you leave for home. And - yes - you have to run to the bathroom quite often. 2-3 liters of water will do the job nicely.

That is also what my physician recommends (But don't try that with sweet or sweetened drinks).