When astronauts return to Earth, they experience 1g conditions, which is the same gravity that they experience on Earth. This means that they are able to stand up and walk without any problems.

However, it is important to note that astronauts do not experience 1g conditions during the majority of their time in space. In space, they experience microgravity, which is a state where the force of gravity is almost non-existent. This can make it difficult for astronauts to perform tasks that require them to be stable on their feet.

In order to counteract the effects of microgravity, astronauts must exercise regularly while they are in space. This exercise helps them to maintain muscle mass and bone density, which are both essential for standing and walking.

When astronauts return to Earth, they must undergo a period of time to readapt to gravity. This process can take several days or weeks. During this time, they may experience dizziness, nausea, and fatigue. However, with time, they are able to fully adapt to gravity and stand up without any problems.