The chair you're sitting in now is likely contributing to the problem. "Short of sitting on a spike, you can't do much worse than a standard office chair," says Galen Cranz, a professor at the University of California at Berkeley. She explains that the spine wasn't meant to stay for long periods in a seated position. Generally speaking, the slight S shape of the spine serves us well. "If you think about a heavy weight on a C or S, which is going to collapse more easily? The C," she says. But when you sit, the lower lumbar curve collapses, turning the spine's natural S-shape into a C, hampering the abdominal and back musculature that support the body. The body is left to slouch, and the lateral and oblique muscles grow weak and unable to support it.
This, in turn, causes problems with other parts of the body. "When you're standing, you're bearing weight through the hips, knees, and ankles," says Dr. Andrew C, Hecht, co-chief of spinal surgery at Mount Sinai Medical Center. "When you're sitting, you're bearing all that weight through the pelvis and spine, and it puts the highest pressure on your back discs. Looking at MRIs, even sitting with perfect posture causes serious pressure on your back."