As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared special content dedicated to Machamp:
Did you know? It grasps its opponents with its four arms and twists them up in an intricate hold. People call it “the Machamp special”. With four arms, it can attack and defend simultaneously. It’s said to have mastered every martial art in the world.
Source: The Pokémon Company