Yes, sitting on the Aeris Swopper without a backrest is not a problem. Indeed, you can also walk without a backrest. The Aeris Swopper is made to allow people to do what they are meant to do while sitting: to move. On traditional chairs it's different. Here, you need a support because you spend a long time rather sitting still. However, the muscles are not made for long hours of sitting without any movement which is why tension and back pain are the result of this sitting posture. However, by being supported by a backrest your muscles become " unfit " again, become weaker and are no longer able to do what they were designed to do: keep the person upright and the intervertebral discs in their place. On the Aeris Swopper, however, your back is always active and in motion. This trains and strengthens the back muscles. If you feel a pinch or soreness from time to time especially while you are getting used to the Aeris Swopper take it as a good sign. Muscles that have been resting for a while may just be waking up again. Then, the best thing you can do is to swing properly in all directions. By doing so, you'll promote blood flow to the muscles and exercise them. In general, exercising is the best recipe against back pain and other consequences of bad posture.