Sorry for interrupting this out of thread thread, but I just want to say that a human being has a mechanical efficiency of 20%, given an intake of 2.500 (Kilo) calories per day and a net power of 0.1 Hp.
You could use more efficient vehicles (like a bike) which would increase your efficiency a lot, but then, that's another matter. A crude estimate
tells you that a professional biker can produce 300 miles per gallon, give or take.
So, overall, walking on foot, your efficiency is a little better than the efficiency of a car of the '70s, but definitely worse than the efficiency of a modern F1 engine, which (I've heard) is one of the most efficient ICEs to date.
For us to have "millions of times the efficiency" of a car (which would give you around 25.000.000% efficiency) we had to go against thermodynamic laws.
However, hey, if the sun is shining, your girlfriend loves you and you feel fine today compared with an ICE, or, if you confront a cold front, you have fought with your mother in law and you feel that F1 deserves to be in the dustbin of history because modern clutches and gearboxes are a sorry artifact that should be replaced by more modern ways to impulse a car like... (like what?) who am I to interrupt.
Please, move on, without taking seriously this out of thread post in this out of thread thread, hopefully, talking about 1st gear and the misterious art of double clutching.