EXS 510
Case Study Essay Question #2: Aerobic Capacity
What is the concept of autoregulation? Autoregulation is a type of blood flow regulation that
locally controls blood flow to fit the bodies current metabolic needs. Blood flow during exercise is quite
an intricate task. Muscles, organs, and other body tissues have the ability to regulate their own blood
flow according to their very own metabolic needs. During exercise the blood flow to skeletal muscle will
proportionately increase to the metabolic demand of the exercise or exercises being performed. Blood
flow to the skeletal muscle at this time can rise 100 times when compared to blood flow to skeletal
muscle at rest. I think it is important to note that while autoregulation moves blood from an area in
lesser need to an area with a greater need, this does not include the brain. Blood flow to the Brain will
remain relatively normal. Although there are three aspects of autoregulation, which will be discussed
later on. It is important in the understanding of autoregulation to know what influences this act may
depend on. Autoregulation is greatly influenced by the oxygen needs of the skeletal muscle tissue, the
amount of C02 in the blood, any changes in the bloods PH level, and changes in the concentration of
other metabolites.
What are the three aspects of autoregulation? There are three aspects of autoregulation.
Vasodilation, vasoconstriction, and capillary recruitment. Let’s start with the first aspect named.
Vasodilation is the increase in diameter of a blood vessel or blood vessels to increase blood flow to a
particular area within the body. This increase in blood flow will in turn increase the delivery of oxygen
and nutrients to the area in need as well. Vasodilation will occur as the body transitions from a state of
rest to a state of exercise. The second aspect of autoregulation is vasoconstriction. Vasoconstriction is
the complete opposite of vasodilation. The reduction of the diameter or radius of a blood vessel or blood
vessels of organs and tissues that at the moment do not need a large amount of blood flow to them. The
blood is shunted from these areas and distributed to the areas of the body that are in need of an
increased flow of blood, oxygen, and nutrients. For example, if I were to cycle for 20 miles, while my
arms are stationary on the bike, blood from my upper body would be shunted from my arms and chest
and redirected towards my legs. Both vasodilation, and vasoconstriction can also occur during a “fight-
or-flight” type situation. The third and final aspect of autoregulation is capillary recruitment. At rest
roughly 5-10% of the capillaries within the body are open. Some of these capillary veins are so small in
fact that red blood cells have to move through them one at a time. During exercise it has been estimated
that 100% of all capillaries are then open due to capillary recruitment. This allows for an increased
volume of blood flow, oxygen, and nutrients.
How can a person physiologically improve their aerobic capacity after several months of
cardiovascular training? Over time it is very possible for an individual to increase their aerobic capacity.
These training induced changes occur due to an increase in maximal cardiac output, maximal Av02
difference or a combination of both. Let’s first take a look at the possibility of increasing cardiac output.
Cardiac output is determined by the product of heart rate times stroke volume. Stroke volume is the
amount of blood that is ejected from the heart with each beat. Long term aerobic training cannot
increase maximal heart rate, but what it can do is increase the size of the heart, by increasing the size of
the heart, importantly the diameter of the left ventricle. Then we can increase stroke volume which will
allow more blood to be pumped with each beat, this in turn will increase maximal cardiac output. We
should also take a look at the possibility of increasing maximal Av02 difference. Av02 difference is the
measure of how much oxygen is removed from arterial blood and used by tissues. This can be made
possible through months of aerobic training, these sum months of training aid in increasing oxygen
extraction from the blood, this change can be attributed to an increase in capillary density as well as a
training induced increase in mitochondrial volume.
In closing, autoregulation is a type of blood flow regulation that locally controls blood flow to fit
the bodies current metabolic needs. It’s three aspects are vasodilation, vasoconstriction, and capillary
recruitment. Each play an intricate part in the process of autoregulation, which occurs during the bodies
transition from a resting state to an exercising state, or even a fight or flight type situation. Several
months of cardiovascular training can physiologically improve maximal cardiac output, Av02 difference
or a combination of both.
References
Powers, S. K. (2020). Exercise Physiology: Theory and Application to Fitness and Performance (11th
Edition). McGraw-Hill Higher Education (US). https://mbsdirect.vitalsource.com/books/9781260813562
EXS 510
Powered by TCPDF (www.tcpdf.org)
