Physical endurance is differentiated from other forms of
physical stress in that in endurance exercise fatigue of the
muscles and cardiovascular system do not force the effort to
end. The need for sleep, the buildup of non-recyclable waste
chemicals, the depletion of convertible energy stores and other
needed chemicals (e.g., water, sodium), physical injury,
psychological failure, or attainment of the goal will bring the
effort to an end.
Ability to maintain or go the distance: work hard for a long or extended amount of time.