Ergonomic experts at Cornell don’t recommend standing desks, instead:
Sit to do computer work. Sit using a height-adjustable, downward
titling keyboard tray for the best work posture, then every 20
minutes stand for 2 minutes AND MOVE. The absolute time isn’t
critical but about every 20-30 minutes take a posture break and
move for a couple of minutes. Simply standing is insufficient.
[A big problem at work, we talk and work on these skills quite a bit. We’ve sat on exercise balls, we’ve changed positions, we stand. We’ll keep trying to make this healthier for ourselves.]
Source: Daring Fireball