Why are endurance athletes able to exercise longer than non-endurance athletes?
There are basically two types of muscle fibers in our bodies
that we have voluntary control over. One is called "red" muscle,
and the other is called "white". Red muscle fibers have the ability
to perform work over longer periods of time without fatigue. White
muscle fibers are able to work hard, but for a shorter period of
time than red fibers. An endurance athlete will have exercised his
or her red muscle fibers (through long exercise sessions), so that
they grow stronger and bigger. This means that their body will have
the ability to do work for much longer than a person who only
exercises for shorter periods (and exercises their white muscle
fibers).