Returning to earth won’t be easy—doctors explain what NASA astronauts will endure

Indian-origin astronaut Sunita Williams is finally preparing to return to Earth after an unexpected nine-month stay in space. Williams and fellow NASA astronaut Butch Wilmore had initially embarked on what was supposed to be an eight-day mission to the International Space Station (ISS) in June last year. However, technical problems with their Boeing Starliner spacecraft extended their stay far beyond the planned schedule.
Now, after months of delays, a return mission is finally in place. NASA, in collaboration with Elon Musk’s SpaceX, has devised a plan to bring them back. SpaceX’s Crew-10 mission is set to launch on March 12, carrying their replacements to the ISS. With their return now scheduled for March 19 or 20 aboard a SpaceX capsule, their rehabilitation will begin the moment they set foot on Earth.
According to medical experts, the astronauts will not be able to walk on their own after landing. They will be placed on stretchers immediately and taken for medical evaluations. Dr. Vinay Gupta, a pulmonologist and Air Force veteran, told DailyMail that their rehabilitation could take up to six weeks, involving guided exercises and a strict nutritional plan to rebuild muscle strength and bone density.

Life in microgravity causes significant physical deterioration. NASA research shows that astronauts lose up to 20% of their muscle mass in just five days and can experience a 1-1.5% decrease in bone density per month. Over a six-month mission, an astronaut can lose half their strength, increasing their risk of fractures and long-term bone loss.
Despite exercising for two hours daily on the International Space Station (ISS), astronauts still experience muscle weakening. Dr. John Jaquish, a biomedical engineer, explained that Earth’s gravity naturally keeps our bodies strong, but in space, the lack of gravitational resistance leads to muscle atrophy and bone deterioration.
Muscle and bone loss aren’t the only concerns. In low gravity, bodily fluids shift upward toward the head, causing changes in cardiovascular function. The heart doesn’t have to work as hard to pump blood, leading to reduced blood volume and weaker circulation. Once back on Earth, Williams and Wilmore will have to recondition their hearts and blood vessels through extensive cardiovascular training.
Radiation exposure is another serious risk. Astronauts on the ISS receive a year’s worth of Earth’s radiation in just one week. Prolonged exposure can increase the likelihood of cancer, central nervous system damage, and cardiovascular diseases. Dr. Gupta suggested that astronauts returning from such long missions may require more frequent cancer screenings.
On top of the physical challenges, the astronauts may also face psychological effects from their unexpectedly extended stay in space.

NASA follows a structured 45-day rehabilitation program for returning astronauts. The first phase focuses on regaining basic mobility and strength. The second introduces proprioceptive exercises—movements that help retrain the body’s sense of position and coordination—along with cardiovascular conditioning. The final phase, which is the longest, works on restoring full physical performance through functional strength training.
However, full recovery is not guaranteed. While muscle strength can be regained, bone density loss may be permanent. To rebuild their bones, Williams and Wilmore will need to undergo osteogenic loading, a specialized form of training that requires bearing loads over four times their body weight—an extreme challenge even for elite athletes.
As NASA prepares for future deep-space missions, including potential trips to Mars, understanding and mitigating these health risks will be critical. For now, Williams and Wilmore’s return marks the beginning of an intense recovery process.