If your dog is genetically sound, you wont need to hang weight around their neck. I was not one that said that it breaks down muscle, so I don't know if it does or not, although I know that overwork without sufficient rest will do that. My big hangup is "does the benefit outweigh the risk?" I haven't seen anything to indicate it does. If people can get their dogs in top-notch shape with hand-walking, flirtpole, maybe a little treadmill, then hanging weight around a dog's neck seems the lazy way out.
If I had two dogs that were bred similar and the same sex, I'd put them both through a conditioning routine -- one with and one without a weighted collar -- just to see if there were tangible benefits with my own eyes. But as I've said ad nauseum, if the competitive conditioners don't use weighted collars, that's good enough for me.
And Sampson, you're cute. Sorry you seem to be pretty much against any measure to make a dog safer. I can't keep a mess of dogs and quickly replace one that gets broken, so I take a few precautions to make sure the ones I have are safe and healthy.