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 an illustration of the spine showing the natural curves.