"If you keep your back straight and you think of gravity as a force that pulls in one direction, downward, like a vertical rod, you can align yourself to this vertical and spare your body from pain."
Your lumbar discs are getting crunched
Your spine is practically begging you to stand. An upright position puts the discs in your lower back in proper alignment and minimizes the pressure they endure. Sitting, on the other hand, forces the vertebrae to crunch down onto each other and bear a lot more force, increasing the risk of chronic lower back pain.
"When you're sitting, your spine is compressing. In space, you get taller by 1-2 inches, and if you lay in bed, you'll also get taller, because your discs are expanding. But when astronauts return from space or people get out of bed, their vertebrae collapse onto each other and cause pain. This is also happening when you sit for a long period of time," said Vernikos.
One big culprit of the pain from a compressed spine is the damage done to the cushioning between the discs.
"The muscles have weakened and the vertebrae start collapsing, squeezing the padding and nerves between the discs. This is a huge source of pain," Vernikos added.