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What Does a Lack of Gravity Do to the Human Body?


When astronaut Scott Kelly spend an entire year in space, he not only impressed the world but also helped NASA with some very important research. Even though we’ve had humans in space for many years, we still don’t know everything about what a lack of gravity does to our bodies. We are specifically developed for the gravity here on Earth, so how do our bodies handle any changes to that equilibrium?


1. Your heart, bones, and muscles become weaker.
Gravity puts our bodies through a lot. We are constantly working against its pull, and all this effort keeps our bones and muscles from deteriorating. Once we get into space, we no longer have to fight against gravity, so our bodies have to do less work. If astronauts didn’t work out consistently, they would quickly lose bone and muscle mass. Even with their regular workouts, astronauts still have to take time to recover once they return to Earth.

2. Gene expression changes.
Scott Kelly’s voyage showed us that something pretty incredible happens as soon as the body enters space, and continues to occur throughout the duration of the stay. According to studies comparing Scott and his twin, Mark, Scott’s genes relating to DNA repair, collagen growth, and immune response, among others, switched on. All of this returned to normal shortly after Scott made it back to Earth.


3. Blood pressure equalizes, resulting in puffy faces and thin legs.
Blood typically pools in the legs, resulting in a difference between blood pressure in the legs and blood pressure in the head. This doesn’t happen when there’s no gravity to pull the fluid down, so it distributes itself equally throughout the body. Appearance-wise, this can make an astronaut’s face look puffy and their legs look thin. In addition, the altered distribution confuses the brain and makes it think the body has too much blood. This can lead to the heart pumping more slowly, which can be dangerous and lead to atrophy.


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