Vader's strike jars Galen's wrists and shoulders, nearly disarming him

A simple double stroke, up and then down, it contained enough power to jar his wrists and shoulders and very nearly disarm him completely. The collision of their lightsabers was blinding. He staggered backward and found himself at the center of a telekinetic storm. His Master seized on his momentary weakness and hurled missiles at him from all sides, hoping to keep him off his guard. For a moment, it worked.

The Force Unleashed I, Chapter 38, Page 437