Looking at human anatomy extensively for many years, the question of posture while sitting has always amazed me. What is the proper way to site? Is a very commonly asked question to health professionals. It took me a while to conclude, but it is the only obvious conclusion. The answer is There is none! This human body is not made to sit in modern day chairs in my opinion. Sitting on a chair will inevitably lead to slouching forward. Initiating the back muscled to maintain a more erect (straight) posture will inevitably overuse back muscles leading to other injuries.
How can you limit injuries which are caused by sitting for long periods of time? The answer is, get up whenever you can. No matter how short the time interval is. If you can get up and walk for 20 seconds, whenever you find yourself sitting for 15 plus minutes, that will be amazing. These time numbers are not scientifically proven to improve health, this is just my opinion using the knowledge I know about the body. Modern society is too addicted to comfort and limit of motion. Constantly moving whenever you can will offer great health benefits. This movement does not have to be strenuous, or involve 500 pounds being balanced on your neck.