Question: Why do your bones get weaker in space?

Siana Jones answered on 17 Nov 2015:

hi Afaf, I didn’t know this so thanks for the question:)

There is a great answer on the NASA website:

“Some of the processes and functions of bones change after the astronaut has lived in microgravity for several days. In space, the amount of weight that bones must support is reduced to almost zero. At the same time, many bones that aid in movement are no longer subjected to the same stresses that they are subjected to on Earth. Over time, calcium normally stored in the bones is broken down and released into the bloodstream. The high amount of calcium found in astronaut’s blood during spaceflight (much higher than on Earth) reflects the decrease in bone density, or bone mass. This drop in density, known as disuse osteoporosis, leaves bone weak and less able to support the body’s weight and movement upon return to Earth, putting the astronaut at a higher risk of fracture”

http://www.nasa.gov/audience/foreducators/postsecondary/features/F_Bones_in_Space.html