> ...who have been sitting at their computers...

> ...sitting down all day...

I am 32. I noticed after years of sitting down that my back and hips began to ache and my body started feeling oldish.

So I recently (two months ago) switched to a standing desk and feel really good. Back pain went away and I feel engaged and on point all day long. I do sit down for lunch and do a couple stretch breaks to break things up but in general I am sold and dont plan to 'sit at a desk all day' for a long time.