The average, fit, adult rider can produce only 75 watts or 1/10hp when
cycling at a continuous 12mph.
From:
Human Powered
The entire human body doesn't generate more than 1.5 HP at peak load, IIRC.
I think this is the basis for PA's moped law, actually. (If it produces more than 1.5HP, has more than 50CC, or goes faster than 25MPH) The first and last are upper limits of human ability.
EDIT: Insert the word "average" between "entire" and "human".
__________________
"¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"
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-- Author kept secret.
Je ne veux pas d'une meilleure vie. Je veux être heureux avec celle que j'ai maintenant.
(I do not want a better life. I want to be happy with the one I have now.)