I do that exact same set-up you describe
for power walking with my dog,
and posted about it to try to encourage others to see how neat it is,
to have both arms free, to be able to swing both arms a full swing, is nice.
Is even a lil nicer than off leash, as i don't have to keep such a close eye on him as he scouts the area for bunnies to chase.
First, i just walked my dog, to make sure he had plenty of stops to pee, etc, so he was comfortable.
Instead of a bungy cord, i put on one my guy's belts, for extra room to fit over a coat,
slipped an extenda-leash handle over the belt,
put harness on dog (just a simple one).
Wa-la! Homemade set up.
Amazing how quickly Buddy was able to calculate just exactly how much time he had, if he ran ahead to sniff at something on the extending leash,
and kept sniffing as i walked by......
til he better come along or his harness would be pulled along. The first few stops he made, i'd call to him, so he'd know, we are not stopping.
Buddy seemed to be playing his own "game" of
"speed-sniffing" all the trees as i power-walked along, ha ha!!!
but we were just power walking, not running. SOUNDS LIKE GREAT PLAN!!
FOR ANYONE DOING THE RUNNING VERSION,
REMEMBER
IF YOUR DOG HAS BEEN SEDENTARY and doesn't often get to
run full-speed,
you should also work your dog up to snuff to get in shape. Some dogs can pull muscles if they go from couch-potato who doesn't run much to a fast paced 5 k run, all at once.