The program tonight featured the question of whether a rock thrown by a mower has the same energy as a .357 magnum. In a word. . . Yup! The rock wasn't as fast, but it was heavier which creates an equal or greater amount of energy.
And another thing, during their experiments, the blade hub shattered when the push mower hit a large rock, causing the blade to fly out of the deck.
So, don't remove the rock guards and be sure to wear sturdy shoes. Really!