Mars is months away at best. When we send people to the space station, for periods of time shorter than a trip to Mars, there is a recovery period before they can properly function on Earth. the same thing will happen to anyone we send to Mars. It is a mission with no return.
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.