I only have a basic knowledge biology, but I've wondered about this before. From a "fully charged" adult male human to dying of lack of nourishment; in case of chemical energy from food, this is often said to be three weeks. If it takes that long for a human to lose energy, how much is held chemically, in joules? It's hard to believe that a human can keep moving for that long with the reserves we have. There's also the energy we gain with each breath, so that's a factor too. Also, if this chemical reserve was used up all at once in a single movement, how much more powerfully would our muscles fire (ignoring inhibition which stops the body from tearing it's own muscles, but then this a hypothetical of the force produced.) If an Olympic Athlete was able to use ALL of the energy to high jump, how far would he or she fly? (taking the destruction of the bone and muscle out of the equation).