Physical Effects of Space

The human spine is compressed by gravity on earth. In a system of microgravity such as a spacecraft, the spine lengthens for up to seven centimeters. Consequently, astronauts are prone to backaches and seem taller in space; however, they return to their normal height once they come back to earth.
Because an astronaut uses his upper-body muscles to move around in the spacecraft, his lower-body muscles, especially the leg muscles, begin to atrophy. An astronaut can lose up to twenty percent of his muscle mass in only two weeks. Muscles are divided into two groups: those that are anti-gravity muscles, which support body weight and other muscles and are comprised of slow-twitch muscle fibers, and fast-twitch muscle fibers. Muscles used for gravity support change their function into rapid response contractile fibers during space flight. Therefore, an astronaut can rapidly lose his muscle strength and tone during a few weeks in space. When he returns to earth, he experiences very sore muscles. An extended period of time in space can therefore be extremely dangerous.

The ,bones like the muscles, also become weaker during space flight. When gravitational force is eliminated, bone calcium as well as phosphorus is excreted in an excessive amount in urine and feces. The bones therefore lose calcium and other minerals; the calcium, in turn, congregates in other parts of the body which can lead to serious health problems such as kidney stones and calcification in soft tissues. Astronauts are also prone to bone fractures. Bone mass loss usually occurs in the upper thighs, hips, and lower spines at about one percent per month. Some of this bone loss is irreversible, and other bone recovery is very slow.

Additionally, studies done on animals in space have shown that bone formation slows down dramatically. Consequently, astronauts must exercise regularly on the spacecraft in order to maintain their bone mass and muscle tone. Onboard exercise with a treadmill and ergometer can help offset the bone loss.
To a typical person, the word “fluid” is associated with water or any kind of liquid. Scientifically, “fluid” is a substance that has the ability to flow and in gravity assumes the shape of its container.If fluids’ motion, this includes bodily fluids, is affected by gravity what happens when we take away the gravity? Look at the human body that enters space… Imagine getting a swollen face that looks like a pumpkin, suffering from what feels like a common cold, and not being able to properly taste your food… all this because the fluids in your body do not feel the pull of gravity.

Just after minutes of experiencing weightless environment, a person’s neck veins begin to bulge and their face becomes puffy. The veins of the neck and face stand out more than normal, eyes become red and swollen. The legs look much thinner. This is the “puffy-faced” and “bird-leg” look that astronauts get.

Why this effect? Fluids in the body either are distributed upwards through assistance of organs like the heart or flow downwards due to gravity. In space, the heart just like on earth is trained to pump blood up to a person’s upper body against the force of gravity. When there is no gravity but the heart continues pumping with the same pressure to veins and arteries, the blood rushes up a to person’s upper body and hence they experience “puffy face syndrome.” On the other hand, the legs grow thinner because there is no gravity to make the fluids drop effortlessly towards them; the blood has to be pumped there by heart. Each leg looses about one liter of volume. Hence “bird-leg syndrome.”

Because of changes like these, people in space suffer space-sickness. They begin to feel sinus and nasal congestion as fluid flows to their chest and their head, and they will continue to feel this throughout the journey.About two-thirds of space travelers experience syndromes such as headaches, dizziness, nausea, stomach problems, and vomiting shortly after entry into the orbit. These symptoms go away within 2 to 3 days after the flight is over, when the body has time to recover.(Antimotion-sickness drugs may be used to treat space motion sickness).