The bodybuilder and actor played the title role in CBS's The Incredible Hulk from 1978 to 1982.
A source told The Sun: "Lou has been visiting Michael to build him up so he can perform his dance routines.
"But Jacko refuses to lift weights. He doesn't want to bulk up."
Ferrigno reportedly said: "Michael is more delicate. Our trainer conditioned him for dancing. He likes me - he feels safe with me, he feels protected. He was nervous about people looking at him when he was training."