While watching astronauts float effortlessly inside the International Space Station (ISS) may seem fascinating, the return to Earth’s gravity is far from easy. Long-duration space missions can leave astronauts struggling with dizziness, nausea, and balance issues, highlighting the physiological toll of space travel.

As NASA astronauts Sunita Williams and Butch Wilmore, along with Russian cosmonaut Aleksandr Gorbunov, prepare to return to Earth on Wednesday aboard SpaceX’s Dragon spacecraft, they will likely experience these challenges firsthand.

For Williams and Wilmore, the eight-day mission aboard Boeing’s Starliner capsule unexpectedly turned into a nine-month stay due to helium leaks and thruster malfunctions, which rendered their spacecraft unsafe for return in September.

Experts note that astronauts often experience symptoms like a “weightless tongue,” wobbly legs, and “baby feet”—a term used to describe the hypersensitivity in their soles as they readjust to walking after months in microgravity. Recovery typically involves weeks of rehabilitation, retraining the body to function under Earth’s gravity.

With space agencies gearing up for longer missions, including deep-space travel to Mars, understanding and mitigating these effects is crucial for the future of human space exploration.