The Washington Post reports that this study varies from past research because it includes weight loads in its calculations. The study's authors say that testing on a model T. rex revealed the king of the dinosaurs would have snapped its leg bones if it tried to run. However, they acknowledged that they could have differently accounted for factors like tendon elasticity.
Still, that's not to say a speed-walking T. rex heading your way wouldn't be terrifying. It would be roughly akin to an elephant charging at you — but with eight-inch teeth.