User blog comment:XGlass Reflection/Ch. 54 Review~ Erwin of the Rebellion/@comment-24278139-20140208224253/@comment-7418318-20140209235626

She was able to crack the floor and crush the knife handle when she was around ten or so years old and not trained, so it's hardly surprising that after all the training (both in skill and physical strength) she could do something like that.