Tension headaches, muscle soreness and back spasms can result. Chronic poor posture can lead to degenerative changes in the spine itself. It won't be able to take daily wear and tear if the parts are always out of kilter. Some people think of good posture as being rigid and stiff. In fact, it's just the opposite.
Good posture is comfortable and natural-looking because it's the normal position.
Hold your head straight, balanced evenly between your shoulders and with your chin parallel to the floor. Keep shoulders, hips and knees level and your feet and knees pointed straight ahead. From the side, your ear, shoulder, hip, knee and ankle should be centered along an imaginary straight line. Hold your head straight and erect, bend your knees and hips at 90-degree angles and keep your feet flat on the floor. Keep your lower back pressed against the chair.