From the Super Mario Wiki
Horizontal Bar is a Gymnastics Event that appears exclusively in the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The objective of the event is to scoe points by performing various moves on the bar. The starting record for this event is 16.200pt(s).
In this event, the player must perform a number of moves on the bar to score points, with the one with the most points winning. To swing their character around the bar, the player must draw a specified number of loops on the touch screen within the time limit, with different ratings and points being given for how quickly it is done. Completing it quickly will be rated as perfect, slower timing rated as great, slower again rated as good and failing to draw enough loops in time being a miss. If the player draws too many loops, they will either be rated good if it is done quickly or bad otherwise. The number of loops the player has to draw increases as the event goes on, with the direction changing every time the character changes direction. After every few loop drawing sections, the character will perform a jump move, either a Wingler, Tkatchev piked or Kolmann, and the player must touch the touch screen once when the character lands, with ratings once again being given depending on how well timed their touch was. If the player fails to touch in time, they will be scored a miss and their character will fall off the bar, and the player will only get a final score of the points earnt up until they fell off. If the player makes it to the end of the routine, they will perform a special move as they jump off the bar, and the player must touch the touch screen again to land, which is once again rated and the points added to their score. The score is only shown at the end of the event or when the player falls off the bar.
1) Swing: Draw loops on the Touch Screen.