For a home run, the ball has to land outside the field of play (not sure if you know how baseball works), so wouldn't the challenge make more sense if you had to go on a run that encircled the neighborhood of a 1 km radius from your home? Staying within the 1 km radius seems like the bunt challenge or maybe a single challenge.
Cristina is not the ball. When a player hits a homer, she goes to all of the bases in the infield and returns to home. Leaving the base paths is frowned upon, going out to the warning track very much so.
(Also, the ball does not have to leave the field, there is a notion of an "inside the park home run".)