My wife and I lost our beloved rescue Beagle Gus about 2 months back. We got him at 3 and he was only 7 when he passed. His first 3 years were hard ones but his last 4 with us were cushy.
One of the things that comforted us was the idea that this would allow us to help another dog. Being a runner, I started researching best breeds to be a running companion and kept coming back to Australian Cattle Dog (Blue Heeler). I ended up finding a 3 year old at a rescue group in TN and felt like it was meant to be.
He can go 6 or 7 miles without blinking an eye and has been on runs as long as 11 miles so far. We've been running on the trails at the State Park near my house.
It's a great place to run for him. Soft surfaces, shade and he can take a dip in the James River to cool off mid run.
Heelers were bred to herd sheep and cattle over long distances all day long and have tons of energy. They say a tired Cattle Dog is a well behaved Cattle Dog and this is what he looks like most days after our runs.
I named him Gump, because well "That boy sure is a runnin' fool."