With the recent return of the Soyuz, I wanted to talk about fluid distribution and the affects of the body in extended periods of zero gravity… while at the same time presenting one little question I have at the end.


Exercise is an important part of the daily routine for astronauts aboard the station to prevent bone and muscle loss. On average, astronauts exercise two hours per day. Since there is no gravity pulling down on them they exert a lot less energy while performing daily tasks. This can result in muscle loss. According to Chis, the affects are so drastic that your bones will literally start to reabsorb back into your body. A large part of why they excersize is so that the muscle loss doesn’t affect them as greatly once they have returned home.

Now… even though the astroNots are keeping themselves strong and fit (in the words of good ol’ Chris), we are still presented with a major issue.

This form of workout still doesn’t help with the displacement of internal fluids within the body. I find this to be rather disconcerting when we stop and consider the fact that the human body is more than 65% water. You have fluid moving all over the place inside the body while in long durations of zero gravity.

NASA worded it like this: More than half of American astronauts experience vision changes and anatomical alterations to parts of their eyes during and after long-duration space flight. It is hypothesized that the headward fluid shift that occurs during space flight leads to increased pressure in the brain, which may push on the back of the eye, causing it to change shape.  The Fluid Shifts Before, During, and After Prolonged Space Flight and Their Association with Intracranial Pressure and Visual Impairment (Fluid Shifts) investigation measures how much fluid shifts from the lower body to the upper body, in or out of cells and blood vessels, and determines the impact these shifts have on fluid pressure in the head, changes in vision and eye structures.

You can look further into this and will find that fluid is shifting in all parts of the body (not just inside the head and brain). Fluids inside the legs can make their way upward and vise versa.

Now, having personally been affected by pneumothorax… this shifting of the fluids causes me to ask, what about the lungs?

But first, what is pneumothorax?

Well, it is the presence of air or gas in the cavity between the lungs and the chest wall, causing collapse of the lung (ie; a shifting of gasses or fluids in the body that could create pressure on the lungs resulting in collapse). Sounds a lot like the displacement affects of zero gravity to me.


Now, if we place the exact same gravitational laws of force on the body to the inside of the body as well, then wouldn’t it stand to reason that breathing on the ISS would require less work also?

With that, what excurses are they doing while in zero gravity to keep the lungs worked up and ready for that return trip? It seems to me that a long duration of zero gravity would prevent the lungs from working as hard as they need to in order to maintain the simple task of breathing while under the regular pressure of actual gravity. When we stop and consider the fact that Valeri Polyakov stayed in zero gravity for 437 days and 18 hours, I have to stop and ask myself… what method did he use to maintain healthy, strong lungs, the same way that you would your muscles with their cheesy workout equipment on the ISS?

What about G-Force of the body (otherwise known as gravitational force)? The return home seems like it would be pretty brutal.


On Earth, gravity gives weight to physical objects and causes the ocean tides. The force of Earth’s gravity is the result of the planets mass and density. This results in Earth having a gravitational strength of 9.8 m/s² close to the surface (also known as 1 g).

One G is the force of Earth’s gravity — it is this force that determines how much we weigh. At 5 Gs, a driver experiences a force equal to five times his weight.

With that in mind… let us go back to the definition of pneumothorax. It is essentially pressure forced against the cavity causing it to collapse. If you weigh zero pounds in zero gravity and spend a year in that environment, how in the world are you casually breathing air after having landed back on earth? Your lungs are officially experiencing the weight of your own body against them for the first time in a long time (not to mention the freaking drastic touchdown that you get when landing the Soyuz).

Having reflected on this for a moment, do you think I would be pausing for a photo-op like Peggy and her friends (celebrating 666 days in space as shown at the top of this post)? No, I would be struggling to breath and in need of a ventilator (assuming my lungs didn’t already collapse upon re-entry, touchdown, or the weight of my own body pressure).

But what do I know, right? I clearly am ignorant.

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