What is the Pokéathlon?
The Pokéathlon is the side competition Pokémon HeartGold and SoulSilver build in place of the Contests their generation is known for. Its Dome stands north of Goldenrod City, beside the National Park, and the format is athletics rather than appeal: you enter a team of three Pokémon into a course of three events, against three rival teams, with medals awarded per species for every course won.
There are ten events in the rotation, from the Hurdle Dash and Relay Run to stranger sports like Lamp Jump, Snow Throw and Goal Roll, and they are dealt into five courses, each named for the performance stat it favours. Every Pokémon carries five hidden performance stats, Speed, Power, Skill, Stamina and Jump, rated in stars and shaped by its species and its nature, which is why a team built for the Power course looks nothing like a team built for Jump.
Training is a kitchen job. Apricorns, which grow all over Johto, go into the Apriblender five at a time; walk 100 steps to blend them and the resulting Aprijuice raises some performance stats and lowers others, so a coach blends toward the course they intend to enter. Beating the house records in all ten events is one of the ways to raise your Trainer Card's level.