I agree with most that's been said already--- if your dog is lagging behind on your runs, there is a reason; I would look there first and resolve that issue. Maybe the dog is tired, or overheated (I notice you live in Florida)..or just doesn't have the stamina for a long run. Not fair to the dog!
I am also not against prongs, if used correctly. I was using a prong collar on my mastiff for a few months- for training, to achieve a better sense of control- until I decided I did not want to use it anymore...I'm done with it.
But to throw a prong on a dog in order to prod it along when there seems to be other issues going on is, in my opinion, just wrong.