We have had people in space for periods almost a year (the Russians have been up longer) and while there is a recovery period on return it doesn’t render them nonfunctional.
That combined with the lower gravity of Mars (38% of Earth) actually bodes well. Then add in the ability to use centripetal force to simulate gravity on the way there and back really lessen that problem.
There ain't no coming back. It will be a one way trip. At best.