Microgravity: Our Bodies Hate It
Living in space isn’t as easy as you think it is
Wouldn’t it be wonderful to live in a world where gravity didn’t exist? You wouldn’t drop objects, you could push heavy things with your fingers, and best of all, you can do crazy tricks such as somersaults and flips in the air.
Wonderful, right? Your body doesn’t think so.
You may have heard of the terms “weightlessness” or “zero gravity” and you may associate that with floating objects. However, these terms are synonymous with what is actually going on, a term referred to as microgravity. Without getting into too much physics, it is “micro” and not “zero” gravity because there is always some form of gravity acting on you, whether it is from Earth, the Moon, Jupiter or some distant star. You may not feel the forces of gravity acting on you, but it is strong enough to influence tides. Think of the Bay of Fundy up in New Brunswick for example. Its famous high and low tides are caused by the Moon’s cyclic gravitational pulls.
Now you may be thinking, what’s so bad about microgravity? Turns out, it’s one of the leading reasons why humans can’t live in space… yet. Let’s take a look at why microgravity causes so many problems for the human race in space.
Edema in the Upper Body
On Earth, we experience 1-g of force. However, in space, that changes and we experience near 0-g forces. Due to the reduction in force, fluids in our body, such as blood, plasma and cerebrospinal fluid begin to “float” upwards, pooling in our upper body. This causes our head and upper torso to swell and become red, which creates what is known affectionately as the Charlie Brown Effect — big head, skinny legs.
Vestibular System Disorientation
Right now, as you are sitting this reading, you can easily tell what direction is up and down. This is because there are little sensors in our ears that can feel the pull of gravity. These little sensors are part of the vestibular system, which is responsible for notifying the brain on the body’s orientation. In space, that pull of gravity is no longer there, and both the brain and our vestibular system gets confused. You could spend hours “upside down” and not know, due to your brain being confused. This is why the International Space Station has arrows indicating up and down so that astronauts can orient themselves the right way. In space, your vestibular system is not the only system that gets confused. Your proprioceptive system can also get tricked. This system is responsible for telling us where our arms and legs are — in other words, it tells your brain about your arms and legs’ positions (hard surface or soft surface). In space, your brain can get confused and may not immediately recognize an arm or leg as part of your body.
Bone Density Loss
Another problem of being in a micro-gravitational state for long periods of time is having your bones lose its density and become increasingly weak. Studies have shown that astronauts on average lose an average of 1% to 2% of minerals in their bone per month, and it takes at least 2 to 3 years for the bone density to come back. In fact, scientists still aren’t sure whether the bone loss continues the more time you spend in space or if it plateaus at some point. This loss of bone density puts astronauts at an increased risk of suffering fractures upon return to Earth, and studies have also determined that the bone structure of astronauts upon return can be compared to those who suffer from osteoporosis. Now why does this bone loss occur? Our bones are constantly changing shape, reshaping themselves to respond to the stresses that we face. Our bones also grow and increase in density when mechanical stress occurs, such as bending your joints, walking, etc. In space, there is a significant lack of these mechanical stresses, to the point where exercise doesn’t do much to help it. Without the stress, our bones won’t be used and it will weaken.
Muscle Mass Loss
Similar to bone density loss, our muscles undergo atrophy, or deterioration in space. This can be seen especially in the gastrocnemius (calf), quadriceps, hamstrings, and groin muscles as these muscles are rarely used due to the lack of gravity. In just one week, astronauts could up to 20% of their muscle mass. This could be dangerous if the astronaut has to perform strenuous activities. Just like our bones, when they are not used and there are less muscle contractions, they will eventually weaken. The only way to reduce muscle loss is through intensive exercise, as each astronaut has to partake in 2.5 hours of exercise per day. This only mitigates the muscle loss and it reduces the efficiency of the astronauts during their mission in space.
Cardiovascular Problems
Bones, muscles, and now your arteries and veins. Microgravity leaves astronauts at a higher risk for cardiovascular disease. This is because of the increase in blood pressure during spaceflight as blood and other fluids pool towards the top of the body. This causes the heart to have to work harder to pump out blood, which can lead to a strain on the heart. In turn, this causes arterial walls to stiffen, which ages the arteries due to the increased strain. Heart disease and diabetes are related, and scientists have discovered that insulin resistance is found to occur during spaceflight, which is likely a result of physical inactivity.
Intracranial Pressure
You think all those problems weren’t enough? Intracranial pressure is considered by NASA as one of the top health risks for astronauts in space. This is a result of — surprise surprise — microgravity. As mentioned before, bodily fluids pool up in the brain, and eventually, blood and cerebrospinal fluids begin to become confined in the skull, which builds pressure. Not only that, blood flow in the area also increases so the blood pressure also increases. The fluids in your skull then put pressure on the brain, which can affect the way astronauts think, concentrate, move and reason. Behavioral changes have also been noted when intracranial pressure increases. Increased intracranial pressure also brings forward other symptoms of spaceflight such as motion sickness, headaches, nausea, and vertigo. However, the one pressing problem noted that comes along with intracranial pressure is the loss of eyesight. As the pressure increases, the pressure around the optic nerve increases, and over time, tissue matter will slowly crush that nerve, making the astronaut increasingly blind. In fact, several scans have shown that astronauts who have just returned to Earth often have tissue that looks warped or swollen, especially right around the optic nerve.
Now you may be thinking at this point if there is any good associated with microgravity if space presents to us so many problems. The good news is that for every problem out there, there is likely a team of scientists that are trying to solve that problem by conducting studies, tests, to fully understand the underlying causes and how exactly it can be fixed. There are a plethora of research projects that are being conducted in space right now and it is only a matter of time before significant breakthroughs occur. The future is bright.
Too long, didn’t read? Here are some key takeaways about humans and microgravity:
- Gravity is always existent — even in space — which is why the correct term for weightlessness is microgravity.
- Microgravity affects our bones, muscles, brain, heart, and causes swelling and increased intracranial pressure, all of which can be potentially fatal.
- There are several research projects underway to solve each of these complex problems.
Thanks for reading! Stay tuned for upcoming articles!
