My son wants to know if Darth Vader isn't able to run or if he just doesn't want to. My recollection is that he never runs, only struts. Even in the new Rebels shows, I can't think of any instances of him running. Perhaps this was written into Lucas' character description "DV never runs!"
Are there any images of him running with full Darth gear on? i.e. not as Anakin.
If he doesn't run, then is this due to immense self-confidence that he doesn't need to, or is it a limitation of his suit or a medical impediment, such as his breathing apparatus not able to keep up with fast-paced breathing?