Thoracic kyphosis is a condition where there is some unnatural rounding in the upper back. You might see it particularly with older adults. It can be the result of medical issues such as arthritis. However, much of excess kyphosis comes from slouching. One of the contributing factors is the time spent at computers. The symptom of kyphosis are the "hump" in the back, the forward position of the head, and stiffness and pain in the neck. The head weighs about 8% of the body weight. I have often told my Pilates participants that it is equivalent to a bowling ball sitting on top of the neck. So imagine what happens when the bowling ball shifts forward. The neck extensors are in contraction to maintain that position. A forward leaning head can increase fatigue, muscle tension and pain to the upper back and neck. In addition to this, even a small forward head placement can decrease blood flow to the brain. The next time you are out shopping and find yourself in front of a 3-way mirror, check out your side view of you head placement. If you are stuck in front of the computer, take breaks to move around and sit up straight!
Resource: Paul Check Scientific Back Training for DSW Fitness