Concrete or Dirt?

I normally keep my females & hurt dogs in kennels & my males & younger dogs on chains & runners. The only negative things I have noticed in other kennels, dogs will get scar tissue from lying on concrete after a while. I have carpet or pads for the dogs to lie on & plan on putting a shelf up for them to jump up on.
As far as activity, it just seems some dogs no matter what age will exercise more then others no matter what they are in. I have some dogs that just lay around, even on a chain & not get much exercise. I have had a couple of young dogs injured on my runners this past year. My running pen is about 75 yards from where I keep my dogs & the hog will run the fence line in the evening & the dogs just go balistic. Had one get the chain up under his front leg & he pulled a muscle under his elbow & another wrapped the chain around his back leg injured it.
There are pros & cons to both.