Cardiovascular athletes, such as Chris Froome, a former Tour de France Champion, are
athletes who participate in sports that depend on large muscle groups, such as swimming, biking,
and endurance marathon runners. These athletes were termed as such due to the response and
changes of the structures of their hearts and the function of the heart due to the strain from long,
high-intensity workouts and races.
Cardiovascular drift is a response of the heart when the athlete has been participating in a
prolonged exercise such as swimming, biking, or running. Cardiovascular drift, according to
Powers et al., is defined as “the increase in heart rate and decrease in stroke volume observed
during prolonged exercise”. (Powers et al., 2021) Stroke volume is the amount of blood pumped
by the ventricles in a single beat. (p. G-10) Cardiac output can increase due to increases “in both
heart rate and stroke volume.” (p. 220) According to Coyle and Gonzalez-Alonso, cardiovascular
drift “is a phenomenon whereby some CV responses begin a continuous time-dependent change,
or “drift,” after ~ 10 minutes of prolonged moderate-intensity exercise (e.g., 50-75% VO2 max)
in a neutral or warm environment.” (Coyle & González-Alonso, 2001) Meaning, that at the
beginning of prolonged exercise, the heart works at a rate to pump oxygenated blood to the lungs
and the rest of the body, but as time passes, and especially if the athlete isn’t hydrating well
enough during the exercise, the heart must pump faster to maintain oxygen levels throughout the
body due to decreased in blood oxygenation. What this means is with dehydration, the blood
plasma levels are decreased, in turn, the ability to have positive venous return of the plasma is
decreased, lowering the stroke volume (SV). Lower blood plasma can also lead to reduced blood
volume, also known as hypovolemia, which in turn, to maintain proper blood pressure, cardiac
output must increase. The heart rate must increase to make up for the decreased stroke volume.
Sometimes, this can lead to sudden cardiac death.
Sudden cardiac death is defined as an unexpected, natural, and nonviolent death
occurring within the first 6 hours following the beginning of symptoms. (p. 235b) It does not
appear that injury to the heart or cardiac system, occurs during prolonged exercise at heart rates
that exceed the normal numbers, but sudden cardiac deaths can happen to anyone during
exercise, especially those with underlying or undiagnosed heart conditions.
Factors that can play a part in cardiovascular drift are length of exercise duration,
intensity of exercise, current cardiac health, hydration status or dehydration status, core
temperature, environmental temperature, and humidity. When an athlete is performing a high-
intensity exercise, such as swimming, biking, and endurance marathons, for a prolonged period,
the heart must work harder to accommodate the increased need of ATP production, aerobically
by oxidative phosphorylation, to supply the muscles with the energy to continue to be able to do
the work. Current cardiac health, meaning individuals with no current diagnosed heart condition
have a better chance of not suffering any effect from cardiovascular drift or sudden cardiac
death. The heart is designed to adjust the amount of blood pumped depending on the requirement
of the activity. The increase in heart rate is done by the sympathetic nervous system, this is also
referred to as the “sympathetic outflow”. Powers et al. states that “humans and other animals that
maintain a rather constant body core temperature are called homeotherms.” (p. 290) The human
body can control “heat loss in response to body temperature changes.” (p. 290) Not being able to
control the core temperature and it raises above normal, due to many factors, can lead to
hyperthermia. Hydration status contributes to the blood plasma and the ability to pump the blood
as well as carry oxygen to the heart and the rest of the body. Taking into consideration the body
creating heat with the use of large muscle groups, raising the core temperature, which promotes
sweating, and increased breathing which gives off vapors or evaporative heat loss, all
contributing to dehydration status. Being dehydrate during the prolonged, high-intensity exercise
will increase the risk of cardiovascular drift. The environmental temperature also plays a part in
how fast the athlete’s body temperature will adjust, as well as the increase of dehydration due to
the body attempting to control its’ skin temperature by sweating. Exercising in moderate to high
humidity also increases the dehydration status of the body and its ability to attempt to cool off
the skin surface temperature.
Decreasing the amount of the work that the body must put out while performing the work
of endurance, high intensity cycling, such as in the Tour de France, can also help in lessening the
affects of cardiovascular drift. This can be achieved by having the advanced technology in the
bicycle and its components, such as the frame, wheels, and tires. Practicing the proper body
positions to achieve low aerodynamic drag, making less work by at least 20%. Wearing of the
proper gear to lessen the airflow resistance. Skintight clothing made from materials such as
Lycra, help with air flow and breathability. Helmet and shoes made from smooth materials and
shape, also help with airflow resistance. Learning how to drag behind another cyclist “can lead to
a reduction in energy cost of cycling by ~30%.” (p. 629) According to Kounalakis and Geladas,
pedaling cadence also has an affect on cardiovascular drift. During the study, they found that
pedal cadence “exaggerated cardiovascular drift at a fast, rather than slow, cycling cadence, and
that faster cadences may compromise regional cerebral and muscle blood volume and cerebral
oxygenation”. (Kounalakis & Geladas, 2012)
References
Coyle, E. F., & González-Alonso, J. (2001). Cardiovascular Drift during prolonged exercise:
New perspectives. Exercise and Sport Sciences Reviews, 29(2), 88–92.
https://doi.org/10.1249/00003677-200104000-00009
Kounalakis, S. N., & Geladas, N. D. (2012). Cardiovascular Drift and cerebral and muscle tissue
oxygenation during prolonged cycling at different pedalling cadences. Applied Physiology,
Nutrition, and Metabolism, 37(3), 407–417. https://doi.org/10.1139/h2012-011
Powers, S., Howley, E. T., & Quindry, J. (2021). Exercise physiology: Theory and application to
fitness and performance. McGraw-Hill.
Lara Malloy
EXSC 510
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