Other source:

As a final act of desperation, Krillin unleashes a powerful Kamehameha upon Piccolo, who is unaffected. After getting what Piccolo thought was a fatal blow, Krillin surrenders; everyone realizes he still did very well. In the next match, Yamcha does not take his seemingly foolish opponent, Hero, seriously. However, Hero decides to battle Yamcha with his real power, exhibiting strength that surprises everyone.