Serebii
Pokéthlon is a new game feature introduced in Pokémon Heart Gold & Pokémon Soul Silver. In the west of the National Park in Johto is the Pokéthlon Dome. This Dome is where a whole new Pokémon contest stands. However, the Pokéthlon is much different to the contests of Hoenn & Sinnoh. The Pokéthlon provides a variety of different games and events for the Pokémon to take part in. You always enter with three Pokémon. There are 10 different activities in the Pokéthlon, but you don't necessarily decide on the ones you play. Instead, you select one out of five categories; Speed, Power, Technique, Stamina & Jump. From there, three activities are chosen based upon that. If you win the activity, you will get "Suron Points" which you can then exchange for prizes.
Once you reach the Pokéthlon Dome a man named Kobushi will approach you with his Poliwrath. He'll refer to Pokemon competing in the Dome as Pokethletes. After this, he'll leave and allow you to enter.
Inside the Pokethlon Dome it's loud and there are videos on the walls of the Johto starters. Whitney runs in and questions if you are going to compete. She tells you that you have to prepare to compete in a Pokethlon and ask for your size. She then gives you a Jersey.
A man outside of the stadium can also take a picture of you and your Pokemon team, which is later viewable in a photo album on your PC. (More on this later!)
Each event gives you points, which you can spend on apricorns, rare candies, and tons of other items!
Now for the actual events! (Information from Serebii for organizations sakes)
Dash Hurdles
This game is a race between your Pokémon and nine other Pokémon. It is a race in a straight line and it is controlled completely through the touch screen. Your three Pokémon are seen running on the top screen and are running essentially on their own. Your control is making your Pokémon jump the hurdles. This is done by simply tapping them on the DS's Touch Screen. The timing of the jump is crucial to build up speed as if you jump too early or too late, your Pokémon will collide with the hurdle. If you get the timing perfect however, your Pokémon will get a boost. You can see the upcoming obstacles on the top screen so you can be prepared for whatever Pokémon you need to make jump.
Even though you cannot see them, this is a race so you are against the clock and will have to try and claim all three of the top positions to obtain maximum points.
Bounce Field
The object of this game is to make your Pokémon bounce upwards by pulling the stylus down and then flicking it up. This sends your Pokémon flying. The task is to hit as many lights as possible to turn them off during the time limit. Like the other events, all three of your Pokémon are in this event at the same time so you can make good use out of this by potentially flicking them in opposite directions.
The angle and depth of the throw is quite crucial to this game as it is possible to get multiple lights at once, thus gaining more points. Once the time limit ends, your score will be tallied against the scores of the NPCs and the winner shall be determined.
Ring Out Fight
The Ring Out Fight game is another of the competitive games in Pokéthlon. Unlike the previous two events, this one has no focus on jumping but instead is similar to a sumo wrestling fight. One of your Pokémon is placed in a ring with three other Pokémon and you have to make sure they stay in the ring and knock Pokémon out of it at the same time. This is done by using the DS's stylus to flick your Pokémon into the other Pokémon. However, there are no walls in the ring so you have to make sure you only put a lot of power into the flick if you're going to collide with a Pokémon.
As you knock Pokémon out of the ring, other Pokémon will come in the ring until the time reaches 0. Once that happens, the Pokémon are ranked and the winner is determined by the amount of remaining Pokémon.
Shooting Snow
The Shooting Snow game is a Pokémon adaptation of a fun winter activity. This event pits your three Pokémon against three other teams of three Pokémon. Here, you are in a classic snowball fight against the other Pokémon. To control it, you just have to flick the Snowballs from your Pokémon to the other Pokémon. As such, the angle of the flick needs to be precise if you are to hit the Pokémon you desire. The power of the flick determines the distance the snowball goes. For each hit, you will get a point
When a Pokémon is hit by a snowball, they are temporarily dazed and will be unable to move or to throw a Snowball. As such, you have to move your Pokémon when a snowball is incoming in order to prevent your opponents getting a hit. This means you have to be focused on what your opponent is doing as well as what you yourself are to do.
Charge Relay
The Charge Relay is essentially another race in a similar manner to the Dash Hurdles. However, this game has you control one Pokémon at a time on a race track. Controlling them by using the Touch Screen, you have to get the optimum speed and pass from Pokémon to Pokémon at a variety of points.
This can get tricky due to the fact that obstacles will sometimes come on the course and you'll have to quickly avoid them so you need to be completely alert in order to win the race.
Break Block
The Break Block activity requires your Pokémon to be strong and quick. You control one Pokémon at a time and you need to destroy the blocks in front of your Pokémon. This is also done on the Touch screen by tapping the blocks. It is best to get a good rhythm with this so that your Pokémon can get into the groove and hit the blocks successfully
Even though you're on your own, this is essentially a race to see who can destroy the blocks quicker and in higher amounts. As such, you need to plan the Pokémon you use strategically so you can win easier
Push Circle
The Push Circle is essentially similar to a game of King of the Hill. There are a variety of circles on the field and you have to control all three of your Pokémon and get them into the circles to gain points. The winners are those that are in the circle the longest. However, it is not as easy as it seems
As you are controlling all three Pokémon, and have nine opponents on the field at once, you will have to think even more strategically and try to push your opponents out of the circle. The smaller circles give you the more points so be sure to aim for those.
Steal Flag
The Steal Flag game is a simple capture the flag game. Your three Pokémon take it in turns to go around the course and collect flags. This is done by flicking the stylus across the touch screen. There are obstacles you have to factor in and move around, as well as the opponent Pokémon.
You can only collect 9 flags at once. In addition to that, you can collide with the opponent's Pokémon and take their flags. Take your flags back to the start and you'll get your third Pokémon sent.
Catch Saucer
The Catch Saucer game requires you to control all three of your Pokémon at all times. The task her is to have your Pokémon jump up and catch the saucers being shot over the field. The point of capture determines the amount of points earned from each catch. You control the movement of all three Pokémon using the Stylus and tap them in order to jump.
In order to make sure your Pokémon get the saucer, you will also have to knock your opponents off of the platform. This will temporarily remove them from play.
Smash Goal
The Smash Goal is a three a-side four team soccer match. You control all three of your Pokémon at once and your task is to shoot balls into the other team's goals as well as prevent the other team from knocking a ball into yours. You control all three Pokéon with the touch screen and a hard flick of the stylus will cause the Pokémon to strongly hit the ball
Each goal results in +1 point to the scoring team and -1 point to the defending team. After a while, several balls start to come on the field at once. After a while, a big gold ball will come which counts for 2 points
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For each 3 events you beat, you get medals. You can view your medals in the basement of the dome.
There is also a back room, but I'm not too sure what that part is. I'll scope for information on that later.
UPDATE!
Once you get a medal in each stat, the back room opens. The first room shows what medals each of your Pokemon have. Though it seems to only go by species as opposed to individual Pokemon.
A girl with an Abra, a man with a Dratini, and a man resembling Kobushi are in this room. Though they don't seem to do anything of importance. There are also three empty desk, most likely for later trophies?
The next room holds a large machines that keeps tracks of your records. Showing scores for each event and what team you used.
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Commemorative Photos!
At various points within the game, you will discover that you can have your photo taken with your partner Pokémon and usually, your team. These photos do not hold much purpose but can show you on the various stages of your journey.
You can get pictures take in front of buildings, with mildly important npc's, even with the Gym leaders, if you fulfill certain requirements!
