* THIS IS MEANT TO SAY 42.195 km*
This is a cumulative achievement in the game which is given for moving a total of 42.195km which is equivalent to a marathon.
Just play the game and you should have it without an issue by the time you finish the game.
You can keep track of your progress using the achievement tracker within the achievement app, or using SmartGlass. It will even display your current progress on TA game stats at the top of the game page.