I think this is a classic case of looking only at a singe factor and saying "this is the answer". If you take their findings to the logical conclusion that the best position is the one that places the least pressure on the spinal discs regardless of any other factors then surely lying down is the best position to be in? I can just see it now, offices all across the country throwing out their desks and chairs and replacing them with beds, ceiling mounted screens but where would you put the keyboard? Seriously though, while it's interested research I can't see it being adopted in the workplace. As one of the comments says, at 135 degrees your going to slide off the chair. You would also have to hold the head and arms in tension to reach any sort of work equipment. One thing that we perhaps could take from this research though, is that when someone is sitting at their desk simply reading a hard copy document or possibly even just reading the screen, then it may be acceptable and even beneficial to sit back and relax and open up that spine.

I had a sense of deja vu. The article is 2006. I can recall it vindicating my somewhat outlier views on posture when it came out at the time - there was quite a bit of media follow-up to the article. I have a real issue with the unchanged-since-Victorian-times 'sit up straight' position advocated as 'the one' without question in any DSE-related advice. Whilst 135 degrees recline is a little unworkable, (although teenagers seem to manage it) the idea that reclining a bit and making the backrest do it's job of supporting the back, seems logical and more practical in real life. This is after all how many drivers sit for hours. The (US) OSHA guidance on posture offers a reclined seated posture, as alternative to the impossible 90 degree piano-player sitting position. In reality it is the need for flat tables / desks (to retain coffee cups, pencils etc) which determines how people traditionally sit at them. Work out how to slope the working elements (keyboard, mouse) to fit the reclined seated posture and you've cracked it. Citizen Smith - you are right, because if you observe how people read longer documents, they tend to sit back and lift the angle of the paper to suit. But by setting up a classic workstation, unless gifted with an extendable and articulated monitor support, reading from screens automatically defaults people into a head forward, frontwards lean, away from backrests and completely the opposite of a healthy posture. I have never found good research as to why sit-up straight is recommended anyway - seems to be just historical from typing school mantra.

That is the weirdest thing ..... Someone sent me the self same article just yesterday when I chastised him for slouching at his desk! I read it tongue in cheek as "one study does not an argument make", and told him this morning that we would not be adopting the horizontal approach thanks very much! I also noted the date of 2006 - if it hasn't been widely adopted in 7 years, chances are it's not suddenly going to become all the rage. As for not sitting on a chair for long periods of time, people have been sitting down for millenia, so this doesn't really compute as a reasonable argument - Darwin, evolution and all that, and if one looks at a skeleton, the natural curvature of the spine allows for sitting in the 90º position rather than the slouch position, so are we supposed to go against the natural shape of the body? Surely this would put more rather than less strain on the body?

I hear you're so busy you barely have time to sit ;-)

As far as I know, standing puts less pressure on the 5th lumbar disc (the lowest mobile vertebrae) than sitting, due to the body being able to transfer weight down the legs, so standing is better. This is probably why the DSE regs recommend frequent breaks from computers or workstations where you're sitting for long periods. If you do have to sit, upright is considered beneficial to spinal health because the curves of the spine are working directly against gravity. Also you have postural muscles which are designed to keep you in the right form while sitting etc, and by using other muscles (i.e. sitting in a poor posture) those postural muscles can become weaker. The postural muscles are one of the reasons for having frequent breaks as by sitting for long periods, you'll wear them out. Same as sitting with your leg tucked under you - you wear the muscles out in a static position (static loading).