Welp, thanks to this thread -- I'm an owner!?
Watta blast! I can remember these things were a "craze" in the eighties, but I just sort of stopped seeing them after a few years...
...But unbeknownst to me I guess they have reprised to
dernier cri... Who knew?
Anyway, my wife and I have decided not to go "airborne"

for a while yet, keeping both feet planted as suggested above. Hopefully this will preclude our incurring stick-man syndrome.
This should be a perfect compliment to running on the off-days! Thanks Kim_in_TN and all!