There is growing concern over the recentincreased incidence of cardiovascular disease (CVD) and poor cardiac-healthrelated problems in developed countries, especially the United States. This paperaims to review the mounting evidence that suggests exercise combats CVD bytargeting risk factors associated with it. Recent Findings Regularphysical activity decreases risk for, and mortality of CVD. Scientificliterature shows that physical activity is positively associated with improvedblood pressure, cholesterol, diabetic factors, Body Mass Index, and coronaryartery function.
Exercise training does this through epigenetic,cardiac-specific, systemic, and skeletal muscle adaptations and modificationsthat alter the risk factors previously mentioned.Conclusion Researchproposes that cardiac health is improved by physical activity, increasing theneed for its promotion from healthcare and industry leaders. Additionalresearch is necessary on the implications of its use alongside pharmacologicaltherapies traditionally prescribed for those at risk of cardiac events.INTRODUCTION:The American Heart Association definescardiovascular disease as an atherosclerotic condition that develops when aplaque-like substance builds up along the artery walls causing narrowing of thearteries. This narrowing makes it difficult for blood to flow, potentiallyleading 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 fromthe Center for Disease Control (CDC), 610,000 Americans die each year fromheart disease, accounting for 1 in every 4 deaths. It is the leading cause ofdeath among men and women and costs the United States at least $200 billionannually including health care services, medications, and lost productivity. Keyrisk factors of poor cardiovascular health include high blood pressure, highcholesterol, type II Diabetes, obesity, physical inactivity, and genetics andfamily history (CDC, 2015).
The American Heart Association recommends150 minutes of moderate exercise per week (30 minutes per day, 5 days a week)to improve overall cardiovascular health. Scientific literature illustratesthat exercise helps in the prevention and treatment of heart disease (2014). Inparticular, it works by improving the risk factors associated with poorcardiovascular health. This review will explore the research that illustratesimprovement 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 consideredto be anything above 130 mm Hg systolic and 80 mm Hg diastolic, has been shownto effectively decrease in response to regular, light-moderate physicalactivity. In a study conducted on 7,875 women between the ages of 63 and 99years old, cardiovascular data including blood pressure was collected andanalyzed alongside levels of physical activity (either light ormoderate-vigorous), which was gathered via accelerometers. Both systolic anddiastolic blood pressures were found to be inversely associated with all levelsof physical activity (LaMonte et al, 2017). This means that over the course ofthe study (one year), blood pressure decreased in response to physicalactivity.
In addition, Touati and colleagues found a similar result in theirresearch that consisted of putting male rats on a 12-week exercise program,while being fed a high-fat diet. Results showed that systolic blood pressuresignificantly and progressively decreased over the duration of the study, evenmore so than simply switching the rats from the high-fat diet to a low-fat diet(2011). CHOLESTEROL Anotherrisk factor associated with cardiovascular disease is high cholesterol, LowDensity Lipoproteins (LDLs) in particular, as well as low levels of HighDensity Lipoproteins (HDLs). This is due to LDL’s role in plaque formation andaccumulation along blood vessel walls, causing narrowing and potentially evenclogging of arteries. Previously, it had been thought that the concentration ofLDLs is what caused adverse cardiovascular health effects; however, in Halleand colleagues’ 1997 study, it was illustrated that the size and density of theLDL particles are more significant, and these are what change in response to physicalactivity. In the study, lipid profiles were analyzed in two groups ofhypercholesterolemic men, one of which was exercise-trained and the othersedentary.
It was found that LDL concentrations were similar in both groups butthe trained group had significantly less small, dense LDLs, and on average, LDLparticles were larger. This is associated with a healthier cardiovascularsystem as larger, less dense lipoproteins are easier to metabolize. Results ofthis study also showed that the trained group had higher concentrations ofHDLs, 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 studyconducted by Williams and colleagues who examined potential changes inlipoprotein concentrations in sedentary, overweight men who followed anexercise program over a one-year period. Results showed that exercisers had anincrease in LDL diameter as well as an increase in concentration of HDL incomparison to the control group and just altering diet alone (1990). DIABETES TypeII Diabetes is also associated with poor cardiovascular health because ofinsulin insensitivity and high glucose concentrations in the blood that result.However, scientific research has illustrated exercise’s positive effects on theincidence of diabetes, glucose uptake, and insulin sensitivity. In a 2001 studyon 522 middle-aged, overweight subjects with impaired glucose tolerance,investigators implemented lifestyle changes that included exercise addition andmonitored the incidence of diabetes after 4 years. During the trial, risk ofdiabetes was reduced by 58% (Tuomilehto, 2001). A potential mechanism behindthis reduced risk was found in a study conducted by Stanford and Goodyear.
Intheir research, it was found that acute exercise activates other molecularsignals that can evade the faulty insulin signaling via pathways that aid intranslocation of GLUT4 in skeletal muscle. Some of these signals includeAMP-Activated Protein Kinase, Calmodulin-Dependent Protein Kinases, anddownstream targets of Insulin- and Exercise-Stimulated Contraction molecules. Additionally,chronic exercise training results in augmented skeletal muscle mitochondria andGLUT4 expression, which both improve insulin-stimulated glucose disposal anduptake (2014). This demonstrates how glucose uptake is positively affected by bothacute exercise and long-term, regular exercise, which decreased the prevalenceof diabetes, which in turn aids in improving cardiac health. OBESITY Inaddition to blood pressure, cholesterol, and diabetes as risk factors forcardiovascular disease, obesity is another factor in which scientificliterature has strongly associated with poor heart health. Body Mass Index(BMI), in particular, that is equal or greater than 30 kg/m2 hasbeen linked to increased lipid and inflammatory biomarkers. In a 2006cross-sectional analysis of 27,158 women, investigators found that high BMIalong with physical inactivity was associated with above average C-reactiveprotein (CRP), lower HDL (<50 mg/dL), high apolipoprotein (>120 mg/dL),and high total cholesterol, all of which are traditional biomarkers that havebeen related to cardiovascular risk and are potential factors in the advancementof atherosclerosis.
It is important to note that physical activity increasesdaily energy expenditure, which when limiting energy consumption, lowers bodyweight. This consequently has a reducing effect on BMI, which in turn lowersrisk for cardiovascular disease by improving the associated biomarkersmentioned. Participants in this study that were physically active generally hadlower BMIs, and therefore, lower incidence of poor cardiovascular biomarkers(Mora et al, 2006). CORONARY ARTERY FUNCTION Atheroscleroticchanges are at the foundation of cardiovascular disease, coronary arterydisease (CAD) specifically. Many of the risk factors previously discussed playa role in the development of the plaque-like substance that plague arteries ofindividuals with CAD.
Physical activity, however, has been shown to directlyaffect coronary artery calcification (CAC). In a Coronary Artery RiskDevelopment in Young Adults (CARDIA) study conducted by Lee and colleagues, aninverse relationship was found between cardiorespiratory fitness levels and CAC(2008). This means that participants with high levels of physical activity hadless calcification of their arteries, which would put them at early risk forCAD.
In a study by Bruning and Sturek, it was found that exercise trainingimproves coronary blood flow (the primary limitation during cardiac episodes)by increasing epicardial vessel vasoreactivity, reducing coronary plaque burdenby improving HDL levels, and improving resistance vessel function throughenhanced vasodilator reserve and from collateral formation (2015). GENETICS Unlikethe previous risk factors discussed, family history of poor heart health is arisk factor that individuals cannot control or change. However, recent researchsuggests that physical activity can alter humans’ epigenetic profiles to combatincreased risk of heart disease. Epigenetics is defined as the study ofheritable changes that are not coded in the DNA sequence itself, and is mostnotably altered by DNA methylation, histone post-transitional modifications,and non-coding RNA.
In a 2017 study, Recchioni and colleagues investigated theepigenetic effects induced by exercise in elderly patients with cardiovasculardisease, focusing on circulating miRNA alterations and DNA methylation inparticular. Results showed that physical activity induced positive epigeneticchanges in terms of mitochondrial biogenesis through the increased peroxisomeproliferator-activated receptor ? coactivator-1? (PGC1)expression. PGC1 is crucial for improved insulin-sensitivity in skeletal musclethrough augmented mitochondrial density and GLUT4 translocation (Popov et al.,2014). Physical activity was also illustrated to induce increased circulationof c-miRNAs that are linked to cardiovascular adaptations. In particular,c-miRNAs associated with development, function, and remodeling of cardiac andskeletal muscle (miR-1, miR-133ab, miR-206, miR-208, miR-486, and miR-4995p);endothelial function, remodeling, and response (miR-21, miR-146a); andangiogenesis (miR-20a-5p, miR-126, miR-126, miR-210, miR-221/222, miR-328) wereall positively linked with physical activity (Recchioni et al., 2017). CONCLUSIONSScientific literature suggests thatphysical activity (PA) reduces the risk of cardiovascular disease bysignificantly impacting the risk factors that present themselves in associationwith the disease.
Not only does exercise reduce the mortality rate of coronaryartery disease by 27%, but it also reduces the risk of CVD-related mortality by52% (Blair et al., 1995). Risk factors associated with the disease include butare not limited to blood pressure, cholesterol, diabetes, obesity, coronaryartery function, and genetic family history of CVD. PA has been shown to increasecirculating HDL, which assists in clearing out harmful LDL cholesterol in thearteries. Additionally, PA is associated with increased size of LDL particles,making them easier to metabolize.
Exercise training promotes increasedmitochondrial function, GLUT4 expression, and alters molecular signaling toimprovise for defective insulin signaling associated with diabetes; all ofwhich improve glucose uptake and usage. Furthermore,PA has been shown to improve coronary artery function by enhancing blood vesselreactivity and decreasing coronary artery calcification. Finally, exercise hasbeen illustrated to increase PGC1 expression as well as circulating c-miRNAsthat positively affect cardiac and skeletal muscle function. These significantcardiac improvements associated with exercise highlights the need for extra PApromotion from healthcare professionals, politicians, and public healthrepresentatives, especially with the expansion of poor cardiac health in developedcountries. Additional research is still needed on how prescribed PA andpharmacological treatment should be used in conjunction to treat cardiovasculardisease.