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How Space Exploration Affects Astronauts’ Bones
The bones of the human skeleton provide
structure and movement by acting as levers
for the attachment of muscles.
Over time, bones change size, shape and density
as a result of the changing pressure and weight,
or load put on the bones, through physical
activity and gravity. The primary load bearing
bones are the long bones of the legs,
pelvis and lower part of the spine.
These contain trabecular bone, a microscopic
lightweight yet very strong bone that,
like a bridge structure,
can support large loads.
Our bones are adapted to the amount of
gravity we experience on Earth.
In the reduced gravity of space, the body
detects less load to bear and begins to thin
what appears to be surplus bone structure.
The result is bone loss.
This happens quickly,
especially in trabecular bone.
On Earth, a woman over 50 who is untreated
for bone loss can lose 2 percent
of hip bone mass in one year.
In space, astronauts can lose the same
amount in a single month.
Upon returning to Earth,
regenerating bone mass can take three times
as long as it took to lose.
NASA research has identified
resistive exercise, like lifting
or moving a weight, as an effective way to
minimize bone loss on Earth and in space.
Astronauts on the International Space Station
perform up to 2.5 hours of exercise
6 days a week to minimize the negative effects
of space flight on their bones and muscles.
NASA’s research into bone loss has helped
to heighten our awareness of the connection
between gravity, activity and ways
the body gets signals for
the creation of new bone.
There is real hope that in continuing to
research how to protect astronauts
from bone loss, NASA may unlock the key
to helping us all keep our bones
strong and healthy
well into our golden years.