Exercise and Instruction

Mark McGraw calls attention to research indicating that twenty minutes of daily exercise can improve long-term memory.

I can believe this, because if I sit for hours the blood seems to pool in my legs. I become sleepy and unproductive. Walking around for even five minutes does more to awaken my mind than a cup of coffee.

Would it be wise for instructors to require that people get up and walk (or at least stretch) every 40 minutes to maximize information retention?

-DD