The Hulk's vocabulary used to be as puny as the puny God he smashed in The Avengers but Thor: Ragnarok changes that with a far more talkative version of the iconic hero. However, now that he has more than just a few lines of dialogue, some changes have been made behind the scenes and Mark Ruffalo has now confirmed that he alone is voicing the character. Previously, Lou Ferrigno did that.
It makes sense that Ruffalo would take over, though, as it means he can deliver both the motion capture parts of the performance alongside the Jade Giant's dialogue on set with his fellow actors.
"When Hulk is speaking, that’s me. That’s me on the day, in my motion capture suit, and they’re capturing my voice." Despite taking Ferrigno's job in the MCU now The Hulk can talk, the actor went on to make it clear he's thankful to him for inspiring his vocal performance here. "That’s who I watched playing the Hulk growing up. It’s definitely a nod to you, Lou. You influenced that."
That means Ruffalo did everything, including performing the roars and fighting moves in The Grandmaster's gladiatorial arena. "I tried to do it all, the stuff I’m physically capable of. I can’t jump through the air like [him]!" Have you seen Thor: Ragnarok? What did you think of his performance?