If you want to keep your muscles healthy, you need a sport that moves all of them. So stuff like rowing, running and billiard are out of question.
Also team sports like basketball, soccer and lacrosse would be awkward due to the lower gravity. It's not that everything seems lighter, it's just that the ball will go anywhere so fast and come down so slow that in the very least those games will not be played as they are here on Earth.
So you need an alternative which does help you move the whole body. Martial arts are one thing to try. But there is another sport that is greatly helped by the lower gravity:
(But don't tell the elf.)
Under martian gravity a dwarf could weight as little as 20 kilograms. It is quite possible for the regular adult to throw them quite a long distance. Mar's surface is mostly soft sand on a lot of places, so even the basic vacuum-suit will do for protection against the impact of the fall. If you are doing the indoor variety with velcro walls, you'll be able to pin them higher than here on Earth.
The movements required in throwing someone involve the whole body, and their weight is the load your muscles need for a good workout.