I've thought about it a little differently - not that Josh needs to work out more now to take things over the top, but rather it seems there is room in the future when his next 'stage' comes to start focusing on fitness even more which will help keep him on that premiere level.
Regarding Mahomes, two things that impressed and kind of surprised me from the Quarterback show was 1) how fiery/competitive he was and 2) him being such a workout warrior. I went away from the show with more respect for him