Exo skeleton with a bunch of sensors that “simulates” gravity when you’re in space by making movements in certain directions harder. Essentially there to fight the bone & muscle problems that occur for space farers. Importantly it knows its orientation so it’s only movements “against gravity” that are harder. You could go all the way with this – little jets that fire so if you jump you fall back “down”.
This could also be used for training athletes on earth (minus the jets). Everything is harder so they wear it all day every day, and then take it off the day of the race and all of a sudden they have the muscle mass to propel someone twice their mass.