When astronauts get in space they use different muscles then when on earth. When you stay in space for months at a time muscles are going to loose complexity and get smaller. Your bones are also going to break down. I think that astronauts should team up with some one who can help them build a room in the space craft dedicated to using those muscles figuring out different equipment and techniques you can use to strengthen those muscles keeping them strong. They could also make a vitamin that'll keep muscles and bones stronger. If they are planning to send people to Mars they need to figure out all the health factors/risks before they send them.