NASA’s One-Year Mission, a branch of its Human Research Program, is investigating how human bodies adapt to life in space, including the apparent decrease in cardiovascular function researchers have recorded in astronauts.

“Adapting to the microgravity environment of space changes the way your brain interprets sensory signals, decreases muscle strength and alters cardiovascular function,” NASA representatives wrote in a company release. “Astronauts will need to overcome these changes to perform critical mission tasks on a journey to Mars.”

Preliminary findings from the One-Year Mission program suggest balance and stability are affected most while in space; smaller movements like tool operation proved to be less altered. It’s possible, according to NASA, that cardiovascular function could decline while in space because movement takes so little effort that the heart isn’t worked like it is when we exercise on Earth.

NASA is continuing to conduct research on how the brain, heart and muscles operate together during spaceflight.

Read more about the investigation here: