I started off the writing-walking at 1.5 MPH and found it annoyingly slow. A more natural pace for me seems to be about 2.4 MPH, although I recently tried out 3.0 MPH and found it not only increased my sweating but also my writing speed. Over time, I suspect I'll see a correlation between walking speed and writing speed until a certain as yet unknown point is reached.
I'm a closet statistics geek. I suck at math, but I love numbers. Go figure. If you're curious about this treadmill thing, here are a few factoids in no premeditated order:
In this picture, I'm using a TrekDesk. They retail for $475. I got lucky, and a friend had a friend who was unloading a slightly used one for $250. If you Google "DIY treadmill desk," you'll find plenty of posts, pages, and videos by people who have taken cheaper approaches than mine. I know of writers who simply strapped a board across the arms of their treadmill. But for better or worse, I'm in this room to write, not build stuff, so I took the easy way and don't regret it.
In the first four weeks of this year, I did my hour or so of morning fiction writing in the rocking chair currently sitting in the corner of my bedroom. In that chair, over those four weeks, I averaged a writing speed of 13.31 words per minute. (I'll pass a typing test at about 60 WPM. Composition speed is much different.) This number is in line with averages measured during the fourth quarter of 2012.
In the second four weeks, with the TrekDesk, I averaged 15.66 WPM, a difference of 2.35 WPM. Obviously, many factors affect composition speed, including everything from the amount of sleep had the night before to how well I've pre-planned the scene(s) for that morning's sessions. But I think four weeks is long enough to note a meaningful change in average. A nearly 18% improvement is significant.
How significant? Figure I'm averaging 90 minutes per treadmill session five times per week. That's 2.35 words multiplied by 90 minutes, or 211.5 extra words per morning. If I'm doing treadmill writing sessions 255 days per year, that's about 54,000 extra words annually. Friends and neighbors, that's a whole novel -- EVERY YEAR -- just from writing while walking on a treadmill.
This. Blows. My. Mind.
Oh, and yeah. The walking is better for my health, too. Forgot that part.