Gardner told reporters: "There's been people talking and chatting about this, but it's a load of rubbish.
"The gaffer's come in and it's the same. Every football club has to work hard. We're working hard — we have to if we want to stay in the Premier League.
"I don't know where this has come from, that Paolo Di Canio will work us harder, because at any club, there's only one place you'll be found out, and that's on the pitch."
Sunderland are 17th in the Premier League and are only out of the relegation zone on goal difference.