Improper posture, especially when walking, puts increased stress on
your back and causes discomfort and damage. The key to good back posture is to
keep the right amount of curve in your lower back.
A healthy back has three natural front-to-back curves that give the
spine an "S" shape. Although there is much natural variation from person to
person, too much curve ("swayback") or too little curve ("flat back") can
result in problems. The right amount of curve is called the neutral
position. See a picture of the
spine showing the natural curves.