In a manga, before the start of a boxing match, one of the boxers looks at his friends in the audience and says:
シャキ〜ン
Then they reply more or less in the same way:
しゃっきい〜ん
What is the meaning of this expression? Is it an onomatopoeic word used to support someone? Since the match has a special prize of one million yen for the winner, could it be 謝金? Here you can see the page where it is taken from. Thank you for your help!