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From Fellrnr.com, Running tips
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* Cardiac output at rest and at moderate intensity exercise remains largely unchanged with training, which is the result of a greater stroke volume at a lower [[Heart Rate]]. (Sometimes the cardiac output will be slightly lower, probably due to greater oxygen extraction by the muscles.) However, at higher intensity exercise the cardiac output is increased, which results in improved performance.
=Circulation Adaptations=
* Endurance training results in an increased number of capillaries in the muscles. The ratio of capillaries to [[Muscle|muscle fibers ]] allows for a greater delivery of blood to the working muscles. In addition, the use of existing capillaries is improved with training.
* The human body does not have enough blood to fully supply all capillaries in the body, and so it will redistribute the blood flow to the most needed areas. Endurance training improves this redistribution, including redistribution within the muscles themselves, providing more blood to the slow twitch fibers and less to the fast twitch fibers.
* Blood pressure at a given exercise intensity is reduced, but at maximum intensity systolic pressure is increased and diastolic is reduced. (Systolic is the higher pressure when the heart beats and diastolic is the lower pressure when the heart is refilling.)
