As has been said many times, Mike is in very good physical shape despite his age. If you really want to know what kind of shape he is in, you can find some videos of his workouts on the internet. Of course he may not move as fast as he used to, but many young boxers can only envy him.
Once you become a boxer you already a boxer also as you see mike Tyson he still having a good body like he still in capable to make a right still he has the name one of the greatest boxer, looks like still at this age he still having a gym to make sure still healthy. But of course, there's a lack in this like not too much fast and active on the ring still he has tons of experience from different fights to use in the match so still higher odds to win is to Mike.