Perhaps it's related to some ancient ninja art or a hidden power within Naruto himself that gets awakened. In the Naruto universe, there are often latent powers waiting to be discovered. This Hercules - like strength could be tied to his Uzumaki heritage or some long - forgotten jutsu. He may initially struggle with this new power, not knowing how to fully utilize it without causing harm to himself or others. But as the story progresses, he learns to master it.