Have you ever tried sitting on a balance ball? It is not recommended if you are concentrating on another task; because you will likely to fall off. A ball has no secure position for your pelvic bones, because of the natural curve in the ball. You will likely put pressure on one side or the other; or remain very still in the middle, with the odd wobble to keep you steady.
Your balance receptors are situated down your spinal column, so that if you move to one side the receptors will instruct your body to change, in order to maintain your sitting balance. Sitting balance is an important position to maintain in your back, rather than constantly leaning back on to the back rest.
If your weight has changed dramatically, or you have had any type of injury that could affect your balance; you should check your balance receptors by asking someone to push you from side to side, to see if you will return to an upright position. If you fall over, then you need some balance training, for energizing the receptors that trigger the righting reflex in your body.
It is not a serious dilemma, but your body may lose this reflex, if you are constantly leaning against a back rest and never using your back independently in an upright sitting position.
When I was sick with viral encephalitis in 1985, I was extremely weak down the right side; almost like a stroke victim. The physiotherapist worked with me daily on a balance ball, for trying to strengthen my sitting balance; before I could even begin to learn to walk again.
Your pelvic bones are the central area of stability in all active mobility of the body and you need to maintain this area as a central core feature to balance your whole body. Try lifting one side off the seat and your body will naturally lean over to that side for maintaining you upright. Now do the same on the opposite side and your body will again naturally lean over to that side for equalizing the balance on that side of your body.
If you are having trouble doing this exercise, then I suggest you sit on the floor and start learning to "bum walk". This means lifting your pelvic bone and pushing it forward, followed by the other pelvic bone; so that you are walking forward using your pelvic bones. Then repeat the process backwards. This is an important exercise to be able to achieve, because when you walk; your body needs to lift your pelvic bone up, in order that the leg can swing forwards.
Lifting your pelvic bones is the correct gait pattern needed for walking. It means that your legs swing forward in an efficient manner, so that you walk with ease and with a more efficient use of energy. If you tire easily in walking, then you may need to analyze the way you walk, so that your gait pattern becomes more energy efficient.
The best way to make sure that you are walking efficiently is to check you're sitting balance first and then your stability in "bum walking" as both these exercises make your gait pattern easier and more energy efficient.
The author is a qualified Occupational Therapist, with an MSc in Health Promotion & PhD research completed in the constructs for sustaining quality of life. She owns company called Active Living Solutions Ltd for selling products that are ergonomic and therefore comfortable for active in daily living. Gail is shifting the parameters of disability aids, to more comfortable, ergonomic products that will enhance quality of life through productive and safe activity. She is starting by selling ergonomic chairs for helping the larger person with back pain. http://www.activelivingsolutions.net/big-and-tall-chairs.html Gail's ideas have come through living through her own experiences of overcoming disability, pain and functional loss, to become more physically active & participatory in daily life again. This was through recovering from severe viral encephalitis, curing pain & functional limitations with osteoarthritis in both thumbs http://www.activelivingsolutions.net/healing-water and erasing postural scoliosis in her spine through cycling.