20km Race Walk is an athletic event that features exclusively in the 3DS port of the Mario & Sonic at the London 2012 Olympic Games. It is based on the real life sport of racewalking, where the athletes must exercise discipline over long distances and keep moving with one of their feet constantly in contact with the ground.
The player actually only plays 2km of the whole race, as the minigame automatically skips to the last stretch of the marathon race through the city. The gameplay is composed of moving the stylus to the beat of the rhythm.
The aim of the event is to get to the finish line ahead of the opponents, just as with any other race; though the athletes must always be walking to the beat of the rhythm without accelerating.
A rhythm is played throughout the minigame, and the player must slide the stylus back and forth in a pendulum fashion, to the precise beat of the rhythm to control the walking pace of their character.
Omochao features on the screen as a referee, regulating the character's walking pace and commanding the player accordingly. If the player's beat perfectly matches the rhythm, the character will gain a brief boost every few seconds as long as the beat is maintained. Beware not to slide the stylus too quickly, or the character will be red-carded on the spot costing valuable seconds.
During the second half of the race, the beat of the rhythm speeds up so the player has to adjust to the faster rhythm and move the stylus at a faster pace.