ISS expeditions last up to half a year, as long as a flight to or from Mars would last. Here I answered to a question dealing with the adaptation of Martian visitors from microgravity to Martian 0.38 g. It mentions Scott Kelly who had hard time to re-adjust to 1 g, but he was a year in microgravity. How do the astronauts on "typical" ISS expeditions re-adjust to 1 g, when returning from space after about half a year, both immediately and long-term? When can they stand up with help and when without help nor any helping tools? When are they fully re-accustomed to the Earth's 1 g?
I'm assuming Martian astronauts would go through the same body exercise regimen as ISS astronauts do, and adapting to Martian gravity would be even easier.