The Frenchman has laid down the gauntlet to his stars by organising double training sessions and extra gym work since arriving at Villa Park.
His fellow countryman Robert Duverne, the fitness coach who famously clashed with Manchester United defender Patrice Evra at the World Cup, was appointed to oversee the intense regime in one of Houllier's first acts in the job.
But the former Liverpool boss has denied suggestions that he is showing disrespect to O'Neill, who transformed the club into a top-six side during his four years in charge.
Houllier said: "I'm not referring to anything that has gone before - never try to push me on that.
"I have too much respect for the manager that was before me to do that.
"It was the same when I took over Liverpool - I never said anything about the person before.
"But every manager has his own philosophy and it is my job with my staff to get the players to accept mine."
His philosophy means extra running for Villa players with captain Stiliyan Petrov claiming he'll soon be fit enough to run back-to-back marathons!
Houllier said: "You need your midfield players to go from box to box. That is the modern game."