Case Study 2: Autoregulation and Cam Oats
The human body is always in the process of homeostasis, which is the process of
maintaining a constant internal temperature. The systems that work to do this are the respiratory
system and circulatory system, which work together as a coupled unit to maintain the flow of
oxygen and carbon dioxide in the body. The respiratory system focuses on oxygen delivery and
tissue waste removal while the circulatory system works to move nutrients and temperature
regulation. However, during exercise, this process becomes harder as the muscles are requiring a
higher demand of oxygen flow in order to perform physical activity. Powers and Howley note
that the body could increase in oxygen demand by 15 to 25 times than when the body is in a
resting state (Powers & Howley, 2018). In order to meet these kinds of demands, two things have
to happen: the amount of blood that is pumped out by the heart has to increase and blood flow
from inactive organs to the skeletal muscles that are being used has to be redistributed.
There are multiple factors that contribute to the body’s ability to regulate this increased
level of blood flow to muscles during exercise, but the most important is called “autoregulation.”
Autoregulation is the “intrinsic control of blood flow by increases in local metabolites…[that]
work together to promote vasodilation to increase the blood flow to the working muscles”
(Powers & Howley, 2018). To understand what that means, it is important to understand the key
terms in the definition. Metabolites are the means that are necessary for the body’s metabolism to
function properly. Examples of these include ATP, nitric oxide, and adenosine, each of which
play a different role in the metabolic process. Vasodilation is the widening of blood vessels.
These two terms are important to understand what exactly is going on when the autoregulation
process is occurring.
There are three aspects that contribute to autoregulation. These aspects are vasodilation,
vasoconstriction, and capillary recruitment where they each play a role in blood being
redistributed throughout the body depending on the muscles and tissues that need it most during
activity (Liberty University, Autoregulation Presentation, 2020). As previously discussed,
vasodilation is the widening of blood vessels. When this occurs, blood is more easily able to
travel through the vessels to get to the muscles and tissues quicker. This aspect normally happens
at the beginning of exercising where the body shifts from rest to active states. This results in an
increased cardiac output. Vasoconstriction is the shrinking of blood vessels. This occurs when
blood is being redistributed and can prevent as much blood getting to muscles and tissues that
may not need as much as other parts of the body during exercise. This also happens at the start of
exercise as a contrast to vasodilation as it will help to increase the blood flow going to the areas
that need by preventing blood from going somewhere else. Both of these processes are
dependent on the type and intensity of the exercise. If the exercise is low intensity, such as a
walk, the needs for blood flow would be significantly lower than a high intensity workout, such
as circuit training, where the muscular needs would be higher and require more blood flow to get
to those muscles that are at work (Powers & Howley, 2018).
The final aspect is capillary recruitment which is another method of increasing blood
flow. Depending on the need of oxygen and nutrients, only certain capillaries are open to certain
muscles and they are not open all the time. When the body is at rest, at most 10% are open,
however, when the body is exercising, 100% of capillaries are open and they dilate to allow the
entry of blood with the required oxygen and nutrient levels needed. Capillaries are small,
specific, and travel in a certain pattern. The path is from the heart to the lungs, back to the heart
to the artery, to the arterioles, finally to the capillaries which travel to the muscles in need, the to
the venules, the veins and finally back to the heart to start the process over again (Liberty
University, Autoregulation Presentation, 2020. This aspect impacts autoregulation in four ways
and depends on the requirements of the muscles and tissues. These four ways are the changes in
other metabolite concentrations, the oxygen needs of tissues, the amount of carbon dioxide
present in the blood, and the changes in the blood’s pH levels.
Cardiovascular training over months will improve an individuals’ aerobic capacity to
perform exercises. For example, we have a client name Cam Oats who desires to improve his
overall health and knows that by improving his cardiovascular health, then he can improve other
aspects of his life. If he does cardiovascular training, his body will begin to undergo changes
over the course of a few months. These changes are called peripheral metabolic changes that are
connected to cardiovascular health and thus linked to a healthier well-being. Changes include
muscle fibers character changes from fast twitch fibers to acting more like slow twitch fibers,
decreased rate of blood flow at the tissue which allows for the maximum amount of oxygen to be
extracted and used, improved perfusion which allows for oxygen to be more easily absorbed,
increased myoglobin which increases the overall flow of oxygen, increased densities of both
capillaries and mitochondria, and finally an increase in oxidative enzymes which improves the
rate of ATP production.
There are also cardiorespiratory changes that will occur over this time period which
would allow Cam Oats to better perform exercises as he continues on the program. His heart
would actually increase in size, which would allow for more blood to be pumped per beat.
Another increase in blood volume being pumped occurs as there is an increase in stroke volume
which allows more oxygen to be delivered at a time. Cam’s heart rate will change as his resting
heart rate will decrease as will his sub-max heartrate, where his max will most likely stay the
same, but could decrease because of training. His respiratory exchange ration will also improve
as he will be able to use more fat as a quicker rate than before training, allowing him to preserve
more of his stored glucose (Liberty University, Cardiovascular Presentation, 2020). Each of these
factors work together to increase his VO2 max, which will allow for an ultimate increase in his
aerobic capacity to perform his exercises especially when he goes from sedentary to active.
Citation
Liberty University. (2020). Autoregulation [Presentation]. Module 2.
Liberty University. (2020). Cardiovascular & Peripheral Training Adaptations [Presentation].
Module 3.
Powers, S.K., & Howley, T. (2018). Exercise physiology: Theory and application to fitness and
performance (10th ed.). New York, NY: McGraw-Hill.
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