NASA astronaut, engineer, and former football player Leland Melvin explains how the human body changes when it leaves the confines of Planet Earth. Your body may become taller, your heart might get smaller and change shape, your bones become more brittle, and your eyesight might weaken, all thanks to the zero-G environment.

These types of challenges are a part of Cosmonaut Mikhail Korniyenko and Astronaut Scott Kelly’s Year In Space mission, which will monitor how their physiology, behavioral health, microbiome, cells, etc may be altered from spaceflight. Bonus research will contrast the findings to the health of Astronaut Mark Kelly, Scott’s Earthbound twin.

Related reading: How astronauts are affected by space exploration.

And a bonus Leland Melvin video, also thanks to Great Big Story: How the NFL Prepared Me to Be a NASA Astronaut.

Watch these next for more background: The One Year Mission in Space – Kelly & Kornienko arrive on ISS and NASA Astronaut Leland Melvin – Chronicles.