If you have never suffered from low back pain, consider yourself one of the fortunate few. Back pain is a common reason for Americans under the age of 45 to limit their activity. It is also a common reason for visits to the doctor and for surgery. There is some good news, though. With or without medical treatment, most people recover from an acute episode in a few days or weeks. But for many people, low back pain becomes a chronic or recurrent condition, often resulting in considerable social and occupational disability.

Many factors contribute to low back pain—inadequate fitness, heavy lifting, poor posture. But our evolutionary history is to blame for our susceptibility to this pain. At some point in the distant past, some of our ancestors decided to stand on two feet, presumably so their hands would be free to fashion tools and use them efficiently. While their reasons were good, going vertical was not without its drawbacks.

Walking around on all fours distributes the force of gravity evenly over the length of the spine. Standing up, however, concentrates this force in one location—the lumbosacral region, just north of the buttocks. Our vulnerability to low back pain is the price we pay for bipedal locomotion.

Several factors can contribute to persistent back pain:

  • Having a work-related injury, particularly if the work environment requires or allows use of improper body mechanics (eg, bending or twisting when lifting)
  • Having poor ergonomics for sedentary workers
  • Having a degenerative disease (eg, arthritis) of the spine
  • Being overweight or obese