Try to take a deep breath in while slouching with your head forward or looking down, then sit up nice and tall with your shoulders back and head up looking straight ahead. Feel how deeply you can breathe with appropriate posture. Most people think that bad posture just looks bad, but there are many other negative side effects of bad posture.
By rolling the shoulders forward and slouching, it is more difficult to breathe. When people sit like this for eight hours in a day, the body is not getting enough oxygen. The cells in the body tell the brain that they need more oxygen, so the person has to take more breaths. This vicious cycle continues because the breaths are not deep enough to fulfill the need of the cells and the person ends up with a subclinical hyperventilation state in their body. This can present as general aches and pains that are not brought on by activity or trauma, tight chest muscles, and shoulder pain.
To counteract this problem, the person needs to begin by stretching the chest muscles and strengthening the middle back muscles. Concentrate on sitting in good posture and breathing with the belly, not the chest.
Being able to take deep breaths allows the body to get more oxygen to needed tissues, which helps to prevent chronic pain. It helps to create relaxation in the muscles and maintains the body in a normal state.
Check your family for correct posture by having them stand at a mirror with their shoulder facing the mirror. Imagine a line from their ear, to the shoulder, to the hip, knee and ankle. If these are not in a straight line, then the posture is not correct and there are stresses on the body in certain areas.