I've now been using the treadmill desk for a month. It's not all beer and skittles and lower body-mass index. It's still hard to really concentrate. In fact, it's not dissimilar to trying to read a magazine while riding an exercise bike: you can do it, but you miss a lot of detail. I do occasionally stop and sit down to make calls or write. My legs are still, frankly, bloody sore by the sixth or seventh hour. After one unwise day of wearing regular shoes, I've had to give up all pretensions to fashion and wear sensible walking shoes in the office.

But I'm also sleeping better, my digestion's improved, and a recurrent pain in my coccyx has absolutely vanished. Perhaps best of all, the rosy glow of exercise self-satisfaction, usually achieved only post-gym torture, is with me all day, every day.