This might seem off-topic, but it's actually very relevant to overall strength and strength training!
Historically, my back has never really given me any problems. Of course, I've strained the odd muscle or few, but I've never had a chronic bothersome condition. A few weeks ago I was worried that that was about to change, as my back started bothering me more and more, even though I was focussing on sitting with correct posture all day. My next workout I tried bent-over barbell rows (a staple), and that made my back hurt more the next day - that was a bit of a mistake.
Since then, I've avoided that exercise and instead replaced it with one-arm dumbell rowing.
Anyway, sitting on a regular chair, even if I try to maintain correct posture, wasn't working - because in order to keep my back in the right position, I had to contract my mid-to-lower back muscles, which was in turn keeping them in a tired state.
Over the weekend I was trying to get work done sitting at my table, but I couldn't concentrate. So finally I researched these ergonomic kneeling chairs that I'd only known about from my brother, who has one, in London, whom I visited last year.
Yesterday morning I rushed out to Staples and bought this one, one on the low end of the range:
www.staples.ca/ENG/Catalog/cat_sku.asp?w...AffixedCode=WW&=&=&=
It says in the description "Not recommended for long periods of use" - and it does tend to hurt my shins after extended use, but that's a heck of a lot better than hurting my back! So far it's been awesome - my back was feeling great yesterday, and today it's getting stronger again.
For all of you who may be active, but have office jobs, these types of chairs may be better for your back than regular "ergonomic" chairs, even those costing several hundreds of dollars.