I run with a waist belt leash and it has been a game changer.  When I was running a lot with a hand-held leash, I found that my gate was just a little lopsided and I was starting to get a sore in ways that didn't happen if I was not running with my dog.  I've never had that problem with the waist leash.  

The one that I have (by TuffMutt) has a small handle near where it clips to the waist part, which I really like because my dog is not perfect and squirrels etc. are a challenge.  It's easy for me to grab it quickly without having to reach down to the handle down by where the leash clips to the dog.