Sitting Up Straight - Correct Seating Posture

Unfortunately, most of the time the reaction may not be the correct one. They will go from a slightly hunched over seating posture to a more vertical posture. They may push their chest out a bit more or expand the shoulders. They will indeed correct themselves to a more “correct” sitting style. 
The problem with this is that, after a while the back muscles will start to get tired and before they even realize it, they will go back to sitting the usual slouched posture. It’s nobody’s fault, it’s just the way it is. In other words, it is human nature. When correct posture is mentioned, the most common image that pops up into people’s mind, is the sitting perfectly erect or sitting in attention pose. This type of posture is not comfortable to hold for long periods of time, therefore it is impractical. Especially if you don ot have the correct type of chair. The attempt to improve posture will be repeated for a long time without any success.
People who attend work and sit in front of a computer all day, and students, know this too well. In both cases, it can be seen as an act of laziness or even disobedience. This is not the case. The simple truth is that many chairs designed today are simply not good enough to help you with good posture while sitting in them. One of the hall marks of a poorly designed chair is a backward sloping of the chair, or the part you sit on. When you sit on this type of chair, the hips are forced to move backwards which in turn puts the hip joints out of order. Put simply, this type of seating position nearly makes proper seating posture impossible. 
This is why people who sit in this type of chair tend to lean their chair forward. If the chair cannot be leaned forward, then they will try to lean their bodies forward. This tendency reflects the body’s natural tendency to find a correct seating posture. However, this is also not a practical long term solution and as time goes by, bad seating posture will become habit forming. The point of all this is that it is time to find a chair that will help you with the right posture.
The first step towards this would be to find a chair that is the correct size or height for you. When sitting in the chair, the feet should not dangle and If the knees are higher than the waist, then it is too short. This is why it is important to have a chair where the height can be adjusted. While seated, the thighs should be parallel to the ground when the feet are placed on the floor. The height should be adjusted to achieve this. The calves, hips and shoulders should be in one line when sitting. 
Next, the chair should allow the hips to touch the back of the chair. When sitting in the chair, it should allow you to keep the knees and feet together comfortably, or without any effort. The shoulders should be in a relaxed position. If all this can be achieved in the chair you are sitting in, then proper seating posture will naturally follow, without much effort. This means the back will be vertical, abdomen will stay relatively flat and the head will stay up. Good office chairs will be able to easily help you accomplish this.