On Tuesday, February 11, 2020 at 12:32:40 AM UTC-5, Jeff Liebermann wrote:
On Sun, 9 Feb 2020 18:47:18 -0500, Frank Krygowski wrote:

How many here have ridden an Ingo?
My hand is raised. (Riding one is a heck of a workout!)

Not me. However, I did attempt to ride an AquaSkipper (Wave Runner),
and failed miserably:
http://human-powered-hydrofoils.com/hydrofoils/aquaskipper/
https://www.google.com/search?q=aquaskipper

Yes, that looks at least as strenuous as the Ingo.

I think one often unrecognized source of a bicycle's efficiency (in terms of energy used per mile) is that a typical bicyclist is not constantly and repeatedly lifting his own mass. One's pelvis and hence his center of gravity maintains a constant elevation, perched on the saddle.

By contrast, walking, running or even standing to pedal (as on a steep hill) moves one's mass up and down. That takes a lot of effort. The Ingo and the AquaSkipper seem to do that even more.

Related: I do some work at two different houses, both of which have workshops and tool storage at basement level. I'm very much aware that if I'm (say) doing some work on the top floor and I forgot to grab the right screwdriver from the basement, the work I do isn't just carrying the screwdriver up two flights of stairs. Instead, it's carrying the screwdriver plus my body weight.

Further related: That's why I occasionally talk about "bike+rider" weight here.

- Frank Krygowski