because you're in a zero G environment,

some really funky things happen to your body.

(upbeat music)

I grew an inch.

Right now, I'm 5'11" but in space I was six-feet tall.

On the ground, gravity compresses your spine,

it pulls you down, the force factor going down.

In space, without gravity pulling your spine down,

every vertebrae has a chance to move up,

which gives you your extra inch of height.

After my spine elongated,

when I went to bed on the first night,

I felt some back pain, some lower back pain,

and so I actually curled up to kind of alleviate that pain,

to kind of stretch it out even more.

A few other ways the body can change in space

are the heart gets smaller and changes shape

because it's not having to pump as hard to pull the blood up

from your feet,

'cause now things are just floating and working

inside your body so it's pumping easier,

therefore the muscle walls actually changes the shape

and they get smaller.

Without gravity, your bones, they change shape

and they lose calcium, and they become more brittle.

So, we run on a treadmill that you strap yourself down to

and you run on the treadmill to actually give loads

into your bones to keep them from atrophying

and losing bone density or calcium.

For some people in space, your intracranial pressure

changes with pushes on your eyeball

and that changes its shape,

therefore requiring you to wear glasses in space,

so it effects your vision.

So, we keep different prescriptions of glasses

on board just in case someone's vision changes.

Any changes in our bodies

and anything that happens in space,

it's worth it for the spirit of exploration.