Physical Activity, Cardiorespiratory Fitness, and Cardiovascular Disease: Key Studies and Mechanisms

Morris Bus Study

Compared conductors (physically active) and drivers (sedentary). Conductors had 50% fewer heart attacks and sudden death from coronary heart disease.

Morris Civil Servants Study

Prospective study of executives. Examined physical activity outside of work.

Longshoreman Study

Dockworkers in San Francisco categorized by light, moderate, or heavy occupational physical activity. Followed for 22 years. Harder work correlated with a lower risk of death from CHD.

Harvard Alumni Study

Questionnaires assessed physical activity during school and current activity levels. Examined the impact on CVD risk.

Cardiorespiratory Fitness (CRF)

Attribute or characteristic; endurance.

Relationship to Mortality

Inversely related to all-cause mortality. 1 MET increase in fitness = 10% decrease in mortality.

Training Programs

Can be used to monitor the effectiveness of training programs.

Advantages of Fitness over PA

More precise measure; less risk of misclassification.

Aerobics Center Longitudinal Study (ACLS)

Institute for Aerobics Research, Dallas, TX (25,000 males, 7,080 females). Time to exhaustion on treadmill used to assess aerobic fitness. 8-year follow-up. Divided into 3 fitness categories.

ACLS Findings

Men in the lowest fitness group had a 70% (1.7 relative risk) increase in CVD-related death compared to higher fitness groups.

Risk factor comparison

Smoking: 1.6, High blood pressure: 1.3, High cholesterol: 1.6, Family history: 1.2.

Moderate fitness

Provides protection against CVD mortality risk factors.

Critical VO2 Max Thresholds

Males: 8-9 METs, Females: 6-7 METs. Below these levels, increased risk for CHD is observed.

Blood Flow

Heart pumps deoxygenated blood to the lungs. Oxygenated blood returns from the lungs to the heart. Heart pumps oxygenated blood to the muscles. Heart receives deoxygenated blood from the muscles.

Determinants of Oxygen Transfer

Increased a-vO2 difference (arteriovenous oxygen difference): How well the body uses available oxygen. Capillary density: Needed to accept increased blood flow; slows red blood cell transit for oxygen diffusion. Increased number of mitochondria: More energy can be used.

VO2 (Volume of Oxygen Consumed)

Direct Fick method: VO2 = Q x a-vO2 difference, where Q = Cardiac Output (HR x Stroke Volume).

Stroke Volume

Amount of blood ejected from the heart.

VO2 Max

Incremental calorimetry (Cycle ergometer or Treadmill). Treadmill: Increase speed or incline gradually. Measure ventilation, carbon dioxide, and oxygen using a metabolic cart.

Criteria for VO2 Max Achievement

HR within 15 beats of age-predicted max HR. No further increase in VO2 with increased workload. RPE > 17 (Rating of Perceived Exertion). Respiratory Exchange Ratio (RER) ≥ 1.1 (RER = CO2 produced / O2 consumed).

Impact of Cardiovascular Diseases (CVD)

Disability: 8 million Americans are disabled due to CVD. Stroke is the second leading cause of disability. ⅔ of heart attack patients do not fully recover.

Definition of CVD

Diseases of the heart and blood vessels.

Types of CVD

Coronary Heart Disease (CHD): Blockage in vessels supplying oxygen to the heart. Angina = Chest pain.

Cerebrovascular Disease

Blockage or bleed in blood vessels supplying oxygen to the brain.

Blockage (ischemic)

Ischemic is death of cells due to lack of oxygen.

Aneurysm (hemorrhage)

Bleeding in the brain.

Hypertension

Elevated blood pressure in arteries.

Heart Failure

Failure of the heart to pump blood properly.

Peripheral Vascular Disease

Narrowing of peripheral arteries.

Rheumatic Heart Disease

Affects heart valves.

Cardiomyopathies

Abnormalities in heart muscle.

Symptoms of Oxygen Delivery Issues

Chest pain, Shortness of breath, Pain in arm, back, or jaw, Sweating and nausea, Indigestion, Low back pain.

Peripheral Artery Disease Symptoms

Numbness/weakness, Sores, Slow hair and nail growth, Weak peripheral pulse, Erectile dysfunction.

Thrombus

A blood clot (solid mass of platelets and/or fibrin) that forms locally in a vessel.

Embolus

A piece of thrombus carried in the bloodstream.

Red Blood Cells

Biconcave shape increases surface area. Flexible. Hemoglobin capacity increased with no nucleus.

Endothelium

Covers the inside of the lumen (blood vessel opening). Restricts permeability of large molecules and cells. Anti-clotting and platelet inhibitor. Regulates blood flow through vasodilators. Inhibits the creation and migration of smooth muscle cells.

Tunica Intima

Most intimate with the endothelium.

Tunica Media

Middle layer.

Tunica Adventitia

Most outer layer.

Atherosclerosis

Disease where fatty plaques are deposited on the walls of arteries.

Exercise Impacts Individual Risk Factors

Hypertension, Triglycerides and cholesterol, Diabetes, Obesity, Endothelial dysfunction.

Endothelial Dysfunction

Vessel walls become sticky. Adhesion molecules increase. Molecules move under endothelial cells (cholesterol, monocytes, macrophages). Inflammatory cytokines increase.

Bypass Surgery

Going around the blockage.

Angioplasty and Stent

Open up blockage and insert a mesh wire frame.

Phase 1

Inpatient hospital phase (critical care unit).

Phase 2

Outpatient hospital-based phase (2-4 months).

Phase 3

Maintenance phase (4-6 months, up to 12 months).

Hypertension Formula

Hypertension = Q x Peripheral Resistance.

Peripheral Resistance

Mean Arterial Pressure / Left Ventricle Output.

Q

Cardiac Output.

Systolic Blood Pressure (SBP)

Pressure in arteries when the heart contracts (left ventricle).

Diastolic Blood Pressure (DBP)

Pressure in arteries when the heart relaxes.

Primary Hypertension

Linked to diet, weight, exercise habits.

Secondary Hypertension

Caused by another medical condition (e.g., pregnancy).

Normal Blood Pressure

<120/80 mmHg.

Elevated Blood Pressure

120-129/<80 mmHg.

Stage 1 Hypertension

130-139/80-89 mmHg.

Stage 2 Hypertension

>140/90 mmHg.

Hypertension Defined

When either or both pressures are elevated.

Hypertension Consequences

Damages vessels and organs.

Hypertension Leads To

Kidney failure, Heart failure, Stroke, Blood clots, Atherosclerosis.

Hypertension is a Silent Killer

Not all people are aware, controlling, or receiving treatment.

Mortality from Hypertension

Increases almost linearly with SBP >115 mmHg; DBP >75 mmHg (>40 years old).

Blood Pressure Determinants

Blood Pressure = Cardiac Output (HR x SV) x Peripheral Resistance.

Stiffness

Increased vasoconstriction; decreased nitric oxide (vasodilator).

Korotkoff Sounds

First sound = Systolic; Second sound = Diastolic (at rest).

24-Hour BP Monitoring

Accurate BP over a day; associate changes with activities; evaluate sleeping BP.

Non-dippers

<10% drop in BP during sleep.

Hypertension Risk Factors

Age, Race, Family history, Overweight or obesity, Physical inactivity, High sodium, Low potassium, Low vitamin D, Alcohol use, Stress.

Hypertension Complications

MI, Stroke, Aneurysms, Heart failure, Kidney disease, Metabolic syndrome, Endothelial dysfunction.

Hypertension Treatments

Diuretics, Beta-blockers, ACE inhibitors, Angiotensin II blockers, Calcium channel blockers.

Lifestyle Changes for Hypertension

Diet, Exercise, Sodium reduction, Weight loss, Smoking cessation, Limit alcohol.

Aerobic Training Effects on Hypertension

Training frequency, intensity, and program length have positive effects on blood pressure.

Strength Training Effects on Hypertension

Overall benefits increased when starting BP was higher, in non-white participants, not taking BP medication, and with >8 RT exercises/sessions.

Cholesterol's Role

Hormones, Vitamin D, Bile (breaks down fatty molecules)

Total Blood Cholesterol Levels

<200 mg/dL = Optimal, 200-239 mg/dL = Borderline, ≥240 mg/dL = High

LDL Blood Cholesterol Levels

<100 mg/dL = Optimal, 100-129 mg/dL = Near Optimal/Above Optimal, 130-159 mg/dL = Borderline High, 160-189 mg/dL = High, ≥190 mg/dL = Very High

HDL Blood Cholesterol Levels

≥60 mg/dL = Protective, 40-59 mg/dL = Acceptable, <40 mg/dL = Major Risk Factor

Risk of High Total Cholesterol

People with have twice the risk of heart disease.

Prevalence of High LDL

About 33.5% of American adults ; 1 out of 3 have it under control; less than half get treatment.

Lipoproteins

Protein, lipids, and cholesterol; different types and subclasses based on size, density, and atherogenicity.

Apoproteins

Solubilize lipids.

Apo A-1

Major protein in HDL; promotes cholesterol efflux from tissues to the liver for excretion (reverse cholesterol transport).

Apo B

Found on LDL, IDL, VLDL, and chylomicrons; synthesized in the liver (LDL, IDL, VLDL) and gut (chylomicrons); associated with atherosclerosis.

Chylomicron

Dietary (exogenous) triglyceride transport; transports TGs to tissues; remaining is converted to VLDL in the liver.

VLDL

Endogenous triglyceride transporter (TGs created in the liver); transports TGs to tissues for energy or storage.

IDL

Left over from the transition of VLDL to LDL by triglyceride removal; has some TG and lots of cholesterol.

LDL

Major transporter of cholesterol; most atherogenic.

HDL

Removes excess cholesterol to the liver (bile acids).

Lipoprotein Lipase

Breaks down fat into fatty acids.

Dietary Recommendations for High Cholesterol

Soluble fiber (5-10 g/d), Omega-3 fatty acids (2 servings/wk), Nuts (1.5 oz/d), Olive oil (2 tbsp/d), Plant sterols/stanols.

Statins

HMG-CoA reductase inhibitors; reduce cholesterol production in the liver; decrease LDL and TG, may slightly increase HDL.

Side Effects of Statins

Constipation, nausea, diarrhea, stomach pain, muscle soreness, muscle pain, muscle weakness (5-10% of patients report muscle complaints); risk for developing diabetes increases.

New Treatment Guidelines

People without CVD who are 40-75 years old and have a >7.5% risk for a heart attack or stroke within ten years.

STRRIDE Study

Participants: 40-65 years old, men and women (N=168, 80% white, 48% female), mild-moderate dyslipidemia.

Exercise Effects on Lipids

Most studies show a decrease in TG with exercise training (-15-20 mg/dL) and an increase in HDL (2-4 mg/dL).

Fatty Streak

Expression of adhesion molecules, LDL-C becomes trapped and modified (oxidized), Monocytes adhere to endothelium, enter the intima, and become macrophages, Foam cells are created, Smooth muscle begins to migrate

Fibrous Plaque

Characterized by a fibrous cap, Smooth muscle, connective tissue, dead cells, Ca2+, foam cells, and some LDL, Endothelial damage continues, Cap thickness, SMC population, and collagen contribute to stability.

Complicated Lesion

Block up to 45% of blood flow, causing ischemia, Can lead to rupture of the artery, causing internal bleeding, Vulnerable plaques become thrombi

Calcified clot

thrombus - embolus, Reduce radius.