It seems that the solution chosen by many office chair manufacturers is an *adjustable* back rest... 1) "Backrest Recline: It is acceptable to sit upright or recline slightly in your chair as long as the backrest is designed for reclined seating. A slightly reclined posture opens up the angle between the hips and trunk, which decreases the stress placed on the low back." Source and further information: http://ehs.unc.edu/workplace_safety/ergonomics/office.shtml#why7 2) "Adjust the back rest so that it supports your lower back and fits the curvature of your spine. If your back rest is not adjustable, you can use a substitute that provides lower back support. This can be a lower back cushion, small pillow or a rolled-up towel." Source and further information: http://www.facilities.udel.edu/ergosmart/vdt_alltogether.htm 3) "Does the chair have a comfortable lumbar (lower back) backrest? Many chairs have cushioned lumbar supports that can be adjusted up and down, that is curved, and that sometimes adjusts forwards and backwards to best fit your lower back shape. If multiple users will use the chair then this type of adjustment may be required. If the chair has a fixed height lumbar support and it feels comfortable when you sit back against this, and you will be the primary user of the chair then a fixed lumbar support may be acceptable. Is the chair backrest large enough to provide good back support? Many chairs have back supports that are large enough to provide mid-back and upper-back support to the shoulder-blade level, in addition to good lumbar support. The back of the chair should not interfere with your ability to move your elbows back behind the torso. When you sit back against the lumbar support is there ample space for hip room? Insufficient hip room can make you sit too far forwards on the seat pan so that you will not have enough thigh support. When you sit in the chair the seat pan should be at least one inch wider than your hips and thighs on either side." "Does the chair backrest recline and support your back in different positions? Moving the back while you are sitting helps to maintain a healthy spine. Look for chairs that allow you to easily recline, that provide you with good back support in different recline postures, and that have a back that tracks where your back is. Locking the chair backrest in one position generally isn't recommended or beneficial to users because this restricts the back support that is provided. Research studies confirm the benefits of using chairs that support dynamic sitting rather than encouraging a static posture." Source and further information: http://www.ehs.pitt.edu/workplace/chair.html