Right now I am surfing the net on my "brand new" treadmill desk. Ever since I hurt my back last January (14 months ago!) sitting is the worst thing in the world for me.
I've been wanting to have a treadmill desk and today I was screwing around trying to take measurements when I realized my circa 1993 Reebok Step fit PERFECTLY with no wiggle or slip. and I can remove it when it is time to run.
This is only for sloooooow walking. The recommended walk speed for a treadmill desk is 1.0 mph, I find 1.1-1.2 slightly more comfortable.
It isnt just about calorie burn either. There is a study that shows that extended sitting actually changes the chemicals produced by your body and lowers the metabolism even more than just "not moving" would predict