All dogs have what's been labled an "oppositional reflex". We don't have it, so sometimes when people train dogs they don't realize that they are sometimes "mis-training".
If you pull a dog with a leash, it's natural for him to pull in the opposite direction. Reason why some dogs drag their owners when they are walked. Feeling the pull backwards will make the dog pull foward harder. While others "slam on the breaks" when they stay behind and are pulled forward.
With this in mind, I've always trained my dog to recall with some type of opposition toward me. I would have someone hold the leash while I go away from the dog. I'll have his favorite motivation (ball, tug, food, toy, etc.) with me and after an euforic petting and praising, I'll show it to him and entice him to get it. Then I'll sprint away from him shouting his name.
Once away, I'll turn around, facing him and say "X, come!!!" It is at this time that the person holding the leash will bring the dog to me. Depending on how the dog is returning, the person will either jog or run. The main thing is to make the dog "work" or "grind it out". Make him dig in to get to you.
Eventually, once the dog gets more proficient, the person holding the dog can let the leash go. This way the dog learns to RUN to you. Distance is a very important factor also. The closer you are to your dog, the slower he'll go to you. That's why when training this excercise you should try to get spacious place for it.
Another thing I do to help increase the speed and to entice the dog to WANT to recall to me faster is to turn around after I've called him and run "away" from the dog as he's coming to me. This will usually create a feeling of urgency in the dog in getting to you, resulting in an increae in speed. Then I would turn again to finish the recall.
And let me tell you ..... there was no better feeling when I competed in obedience than to hear the round of applause my dog got from the spectators after doing a running recall (or drop on recall in CDX) in a competition. I hope this helps. Happy training.