There with poor cardiovascular health. This review

There is growing concern over the recent
increased incidence of cardiovascular disease (CVD) and poor cardiac-health
related problems in developed countries, especially the United States. This paper
aims to review the mounting evidence that suggests exercise combats CVD by
targeting risk factors associated with it.

Recent Findings

            Regular
physical activity decreases risk for, and mortality of CVD. Scientific
literature shows that physical activity is positively associated with improved
blood pressure, cholesterol, diabetic factors, Body Mass Index, and coronary
artery function. Exercise training does this through epigenetic,
cardiac-specific, systemic, and skeletal muscle adaptations and modifications
that alter the risk factors previously mentioned.

Conclusion

            Research
proposes that cardiac health is improved by physical activity, increasing the
need for its promotion from healthcare and industry leaders. Additional
research is necessary on the implications of its use alongside pharmacological
therapies traditionally prescribed for those at risk of cardiac events.

INTRODUCTION:

The American Heart Association defines
cardiovascular disease as an atherosclerotic condition that develops when a
plaque-like substance builds up along the artery walls causing narrowing of the
arteries. This narrowing makes it difficult for blood to flow, potentially
leading to blood clots that could clog arteries and lead to a heart attack,
stroke, and even death. In fact, according to the most recent statistics from
the Center for Disease Control (CDC), 610,000 Americans die each year from
heart disease, accounting for 1 in every 4 deaths. It is the leading cause of
death among men and women and costs the United States at least $200 billion
annually including health care services, medications, and lost productivity. Key
risk factors of poor cardiovascular health include high blood pressure, high
cholesterol, type II Diabetes, obesity, physical inactivity, and genetics and
family history (CDC, 2015).

The American Heart Association recommends
150 minutes of moderate exercise per week (30 minutes per day, 5 days a week)
to improve overall cardiovascular health. Scientific literature illustrates
that exercise helps in the prevention and treatment of heart disease (2014). In
particular, it works by improving the risk factors associated with poor
cardiovascular health. This review will explore the research that illustrates
improvement in blood pressure, cholesterol, diabetic conditions, obesity, genetics,
and overall cardiovascular system health as a result of exercise.

BLOOD PRESSURE

            High blood pressure, which is considered
to be anything above 130 mm Hg systolic and 80 mm Hg diastolic, has been shown
to effectively decrease in response to regular, light-moderate physical
activity. In a study conducted on 7,875 women between the ages of 63 and 99
years old, cardiovascular data including blood pressure was collected and
analyzed alongside levels of physical activity (either light or
moderate-vigorous), which was gathered via accelerometers. Both systolic and
diastolic blood pressures were found to be inversely associated with all levels
of physical activity (LaMonte et al, 2017). This means that over the course of
the study (one year), blood pressure decreased in response to physical
activity. In addition, Touati and colleagues found a similar result in their
research that consisted of putting male rats on a 12-week exercise program,
while being fed a high-fat diet. Results showed that systolic blood pressure
significantly and progressively decreased over the duration of the study, even
more so than simply switching the rats from the high-fat diet to a low-fat diet
(2011).

CHOLESTEROL

            Another
risk factor associated with cardiovascular disease is high cholesterol, Low
Density Lipoproteins (LDLs) in particular, as well as low levels of High
Density Lipoproteins (HDLs). This is due to LDL’s role in plaque formation and
accumulation along blood vessel walls, causing narrowing and potentially even
clogging of arteries. Previously, it had been thought that the concentration of
LDLs is what caused adverse cardiovascular health effects; however, in Halle
and colleagues’ 1997 study, it was illustrated that the size and density of the
LDL particles are more significant, and these are what change in response to physical
activity. In the study, lipid profiles were analyzed in two groups of
hypercholesterolemic men, one of which was exercise-trained and the other
sedentary. It was found that LDL concentrations were similar in both groups but
the trained group had significantly less small, dense LDLs, and on average, LDL
particles were larger. This is associated with a healthier cardiovascular
system as larger, less dense lipoproteins are easier to metabolize. Results of
this study also showed that the trained group had higher concentrations of
HDLs, which is meaningful for our purposes, as HDLs are known as the “good”
cholesterol that aids in clearing out LDLs from the blood stream.  A similar result was found in a study
conducted by Williams and colleagues who examined potential changes in
lipoprotein concentrations in sedentary, overweight men who followed an
exercise program over a one-year period. Results showed that exercisers had an
increase in LDL diameter as well as an increase in concentration of HDL in
comparison to the control group and just altering diet alone (1990).

DIABETES

            Type
II Diabetes is also associated with poor cardiovascular health because of
insulin insensitivity and high glucose concentrations in the blood that result.

However, scientific research has illustrated exercise’s positive effects on the
incidence of diabetes, glucose uptake, and insulin sensitivity. In a 2001 study
on 522 middle-aged, overweight subjects with impaired glucose tolerance,
investigators implemented lifestyle changes that included exercise addition and
monitored the incidence of diabetes after 4 years. During the trial, risk of
diabetes was reduced by 58% (Tuomilehto, 2001). A potential mechanism behind
this reduced risk was found in a study conducted by Stanford and Goodyear. In
their research, it was found that acute exercise activates other molecular
signals that can evade the faulty insulin signaling via pathways that aid in
translocation of GLUT4 in skeletal muscle. Some of these signals include
AMP-Activated Protein Kinase, Calmodulin-Dependent Protein Kinases, and
downstream targets of Insulin- and Exercise-Stimulated Contraction molecules. Additionally,
chronic exercise training results in augmented skeletal muscle mitochondria and
GLUT4 expression, which both improve insulin-stimulated glucose disposal and
uptake (2014). This demonstrates how glucose uptake is positively affected by both
acute exercise and long-term, regular exercise, which decreased the prevalence
of diabetes, which in turn aids in improving cardiac health.

OBESITY

            In
addition to blood pressure, cholesterol, and diabetes as risk factors for
cardiovascular disease, obesity is another factor in which scientific
literature has strongly associated with poor heart health. Body Mass Index
(BMI), in particular, that is equal or greater than 30 kg/m2 has
been linked to increased lipid and inflammatory biomarkers. In a 2006
cross-sectional analysis of 27,158 women, investigators found that high BMI
along with physical inactivity was associated with above average C-reactive
protein (CRP), lower HDL (<50 mg/dL), high apolipoprotein (>120 mg/dL),
and high total cholesterol, all of which are traditional biomarkers that have
been related to cardiovascular risk and are potential factors in the advancement
of atherosclerosis. It is important to note that physical activity increases
daily energy expenditure, which when limiting energy consumption, lowers body
weight. This consequently has a reducing effect on BMI, which in turn lowers
risk for cardiovascular disease by improving the associated biomarkers
mentioned. Participants in this study that were physically active generally had
lower BMIs, and therefore, lower incidence of poor cardiovascular biomarkers
(Mora et al, 2006). 

CORONARY ARTERY FUNCTION

            Atherosclerotic
changes are at the foundation of cardiovascular disease, coronary artery
disease (CAD) specifically. Many of the risk factors previously discussed play
a role in the development of the plaque-like substance that plague arteries of
individuals with CAD. Physical activity, however, has been shown to directly
affect coronary artery calcification (CAC). In a Coronary Artery Risk
Development in Young Adults (CARDIA) study conducted by Lee and colleagues, an
inverse relationship was found between cardiorespiratory fitness levels and CAC
(2008). This means that participants with high levels of physical activity had
less calcification of their arteries, which would put them at early risk for
CAD. In a study by Bruning and Sturek, it was found that exercise training
improves coronary blood flow (the primary limitation during cardiac episodes)
by increasing epicardial vessel vasoreactivity, reducing coronary plaque burden
by improving HDL levels, and improving resistance vessel function through
enhanced vasodilator reserve and from collateral formation (2015).

GENETICS

            Unlike
the previous risk factors discussed, family history of poor heart health is a
risk factor that individuals cannot control or change. However, recent research
suggests that physical activity can alter humans’ epigenetic profiles to combat
increased risk of heart disease. Epigenetics is defined as the study of
heritable changes that are not coded in the DNA sequence itself, and is most
notably altered by DNA methylation, histone post-transitional modifications,
and non-coding RNA. In a 2017 study, Recchioni and colleagues investigated the
epigenetic effects induced by exercise in elderly patients with cardiovascular
disease, focusing on circulating miRNA alterations and DNA methylation in
particular. Results showed that physical activity induced positive epigenetic
changes in terms of mitochondrial biogenesis through the increased peroxisome
proliferator-activated receptor ? coactivator-1? (PGC1)
expression. PGC1 is crucial for improved insulin-sensitivity in skeletal muscle
through augmented mitochondrial density and GLUT4 translocation (Popov et al.,
2014). Physical activity was also illustrated to induce increased circulation
of c-miRNAs that are linked to cardiovascular adaptations. In particular,
c-miRNAs associated with development, function, and remodeling of cardiac and
skeletal muscle (miR-1, miR-133ab, miR-206, miR-208, miR-486, and miR-4995p);
endothelial function, remodeling, and response (miR-21, miR-146a); and
angiogenesis (miR-20a-5p, miR-126, miR-126, miR-210, miR-221/222, miR-328) were
all positively linked with physical activity (Recchioni et al., 2017).

CONCLUSIONS

Scientific literature suggests that
physical activity (PA) reduces the risk of cardiovascular disease by
significantly impacting the risk factors that present themselves in association
with the disease. Not only does exercise reduce the mortality rate of coronary
artery disease by 27%, but it also reduces the risk of CVD-related mortality by
52% (Blair et al., 1995). Risk factors associated with the disease include but
are not limited to blood pressure, cholesterol, diabetes, obesity, coronary
artery function, and genetic family history of CVD. PA has been shown to increase
circulating HDL, which assists in clearing out harmful LDL cholesterol in the
arteries. Additionally, PA is associated with increased size of LDL particles,
making them easier to metabolize. Exercise training promotes increased
mitochondrial function, GLUT4 expression, and alters molecular signaling to
improvise for defective insulin signaling associated with diabetes; all of
which improve glucose uptake and usage.  Furthermore,
PA has been shown to improve coronary artery function by enhancing blood vessel
reactivity and decreasing coronary artery calcification. Finally, exercise has
been illustrated to increase PGC1 expression as well as circulating c-miRNAs
that positively affect cardiac and skeletal muscle function. These significant
cardiac improvements associated with exercise highlights the need for extra PA
promotion from healthcare professionals, politicians, and public health
representatives, especially with the expansion of poor cardiac health in developed
countries. Additional research is still needed on how prescribed PA and
pharmacological treatment should be used in conjunction to treat cardiovascular
disease.