Four of five Americans report they ve had<br >back trouble--making the back-pain* industry<br >a $30-billion-a-year business.<br > Conventional medical wisdom: Back pain is<br >caused by structural abnormalities of the spine<br >(such as arthritic and disc disorders)， or by a<br >vague group of muscle conditions linked to<br >poor posture， lack of exercise or overexertion.<br > Conventional treatments: Surgery， traction，<br >acupuncture， nerve blocks， biofeedback， deep<br >massage and extended bed rest.<br > These approaches may bring temporary<br >relief (through what I think is a placebo<br >effect)， but they fail to resolve the problem.<br > As a result， the pain recurs...and recurs.<br >And millions of people have barred them-<br >selves from normal physical activity--from<br >raking leaves to going to work. Back pain is<br >the leading cause of worker absenteeism.<br >*For my purposes， back pain refers to discomfort in the<br >neck， shoulders， back or buttocks.<br >