400m (or 400m Dash) is an Athletics event in both versions of the game, Mario & Sonic at the Olympic Games and can be found in the "Track" section of the "Athletics" category. The goal of the event, is to reach the finish line first. The smaller version of this event is 100m.
 Wii Version
Racers will begin the race at their respective starting line. When the announcer announces On Your Marks and Get Set pressing on the Wii-mote will cause the characters to ready themselves and build up for a Start Dash. Once Go appears on the screen, releasing and swinging down the wii remote will give the player a boost. Running is controlled by alternating the movement of the wii-mote and Nunchuk (or just the Wii Remote if not using the nunchuk). Pacing oneself is the key to this event. A gauge appears above the controlled character and when racers begin to sprint (the speed meter is full and characters gain a bluish glow) their stamina begins to drain. If characters' stamina are depleted, they will slow to a walk until their meter replenishes. At the last 100 meter (straightaway) the participants will sprint their way to the finish line.
 DS Version
The event properties are the same in the DS version. The start dash however is preformed by touching the touch screen with the Stylus and then releasing it when the gunshot is heard. Running is controlled by rubbing the stylus across the touch screen. The speed of the runner is determined by how fast the stylus is swiped across the screen.
 Wii Version
Knuckles' fourth mission in the Wii version of Mario & Sonic at the Olympic Games is 400m. To complete it Knuckles must cross the finish line before his rival does. If his rival crosses the finish line first, he will lose the race and the challenge. Knuckles' rival is Vector the crocodile, a slow character though knuckles is pretty slow as well.
Blaze's third mission in the wii version is 400m. Blaze must win the mission by crossing the finish line before her rival crosses it. Her rival is non-other than her best friend in the world, Amy! Another hitch in her giddy-up is that she will have to wait for two seconds at the start of the race until she can start yet she still must pass Amy or else she will lose the challenge.
Shadow's fifth mission in the wii version is 400m. Shadow must win the race by crossing the finish line before both his rival and his clone does. His rival and clone is, obviously, Sonic! Sonic is a speed character and will therefore be incredibly hard to out-speed and win the race against. However if Shadow does not win the race, he will not win the challenge either.
Luigi's fourth mission in the wii version is 400m. It is a hard challenge to win as he must race to the finish line and cross it before all of the other competitors cross it. At the finish line, Luigi must speed up drastically so that he uses up all of his energy as the last part of this mission's requirements is that Luigi stagger, have no energy but still be running, across the finish line in first place.
Princess Peach's fourth mission in the wii version is both 400m and the same as Luigi's fourth mission in the wii version. To win, she must cross the finish line before all other competitors cross it. Once again, the only catch is that she must stagger across the finish line by using it all in the short stretch of land before it by holding the A button to sprint. If she does not stagger across the finish line, she may as well not cross the finish line because she will lose the challenge if she does.
 DS Version
Knuckles' second mission in the DS version of Mario & Sonic at the Olympic Games is 400m. To win it Knuckles must cross the finish line not in first place but in second place. If he crosses it in either first place or any other place below second place, he will lose the challenge however if he crosses the finish line in first place he will win the race.
Sonic's sixth, final and hardest mission in the DS version is 400m. To win this mission of missions, Sonic must do what he does best; run. Sonic must run as fast as he can to defeat his rival to the finish line or he will lose the challenge. Sonic's rival is none other than Nintendo's mascot, Sonic's inspiration, the crime-fighting, drain-fixing, pain-in-the-drain plumber; Mario! Mario will be at super fast speed as he is in top condition so Sonic will have to run very fast and conserve his strength well to catch up to and beat the plumber.
 Dr. Eggman
Dr. Eggman's second mission in the DS version is 400m. In this mission, Dr. Eggman must come in first (cross the finish line before his, randomly chosen, competitors do) but he will be slowed down not by a handicap but bye the fact that if his energy goes to low and he staggers even once during the whole entire race, he will lose the challenge.
Bowser's third mission in the DS version is 400m. To win it, he must win the race by crossing the finish line before all of the other competitors, the other racers, cross the finish line. The hard part of this mission is not that Bowser belongs to the worst category for speed in the game, the power category, and it is not that he is the slowest out of all the characters in that category. It is that he loses one second as a handicap at the very beginning of the challenge to add difficulty to the mission.
Wii version: From a staggered start, kick off from the starting blocks, then endure a 400 meter run to the finishing line. The final 100 meter stretch should be sprinted to get you ahead of the competition, but take it slower at the start to avoid wearing yourself out.
DS Version: In the 400m, it is vital to pace your stylus control so your character does not over exert themselves and lose speed.