[3][4] Astronaut Scott Kelly and cosmonaut Mikhail Kornienko spent 340 days in space with scientists performing medical experiments.

[10] The mission supported the NASA Twins study, which helps shed light on the health effects of long-duration spaceflight.

[11] The goal aboard the orbiting laboratory was to understand better how the human body reacts and adapts to the harsh environment of space.

They worked to develop and validate better countermeasures against the risks associated with future missions around the Moon, asteroids and ultimately Mars.

[12] In November 2012, NASA, the Russian Federal Space Agency (Roscosmos), and their international partners selected two veteran spacefarers for a one-year mission aboard the ISS in 2015.

The study also required the astronauts to keep a journal, and investigated the psychological effects of living in a confined space for an extended length of time.

In addition, some factors were significantly affected by the stress of returning to Earth, including inflammation cytokines and immune response gene networks, as well as cognitive performance.

The effect is rapidly reversed after returning earth and ultimately fall back to near preflight level after 6 months (190 days).

The International Space Station developed exercise equipment, including treadmills and resistance devices to limit muscle atrophy in a low gravity environment.

[20] In March 2022, NASA's Mark T. Vande Hei and the Russian Pyotr Dubrov landed, following 355 days in space as part of ISS Expeditions 64/65/66.