As the human body
exerts itself, it produces fatigue poison
s, mostly as a byproduct
of metabolizing glucose
. These chemicals build up in the body, eventually causing a feeling of exhaustion
. Larger amounts, however, can produce interesting side effects
, which is why people who've stayed up late tend to get silly
. Eventually the buildup
becomes too great and the subject is forced to sleep
so the body can focus on the removal of the poisons. Massage
may also be helpful.
Interestingly enough, a Google search on the topic yielded quite a bit of information on various comic book characters. The significance of this is unknown.