[abound]

Seconding the treadmill desk (if one's situation allows). My previous job had one for communal use, and once I started working remotely, I picked up the same model (LifeSpan TR1200-DT5) on Craigslist.

I get in between 2 and 10 miles depending on the day, and have a little drafting chair that's intentionally pretty mediocre to encourage walking instead.

I find the idea of intentionally interrupting myself every 20 minutes kinda insane, seems like it would preclude getting "deep" work done.