Lifting Thor's hammer has nothing to do with strength.
WRONG
It's only hard to lift if you are unworthy. Spikes don't pop out of the handle, it doesn't become invisible, it's not fucking electrocuted, it merely becomes inhumanly heavy. Odin's spell must manifest in the physical world by exerting some type of force (or weight). If not, then the spell would have no effect.
The strength of Hulk is such that he's able to overcome the power of that spell.