Cardiovascular Health: Physical Activity

• Physical activity has a number of biological effects which provide physiological protection from cardiovascular conditions.

Biological Plausibility

• Exercise lowers blood lipids and LDL-cholesterol, but raises HDL-cholesterol levels.
• Increased fat oxidation and increased energy expenditure can decrease obesity risk.
• Muscle contraction from exercise improves insulin sensitivity.
• Physiological adaptations reduce heart rate and blood pressure at sub-maximal efforts.
• Lower blood viscosity reduces blood clotting effects.
• Active individuals tend to adopt other healthy behaviors.
• Reverse cholesterol transport involves the movement of cholesterol from body cells to the liver, facilitated by HDL.

Physical Activity and Blood Lipids

• Endurance athletes have higher HDL-C levels compared to untrained individuals.
• A dose-response relationship exists between running speed and HDL-C levels.

Marathon Study Results

• LTPA(Leisure Time Physical Activity) self-reported by 537 men
• After adjusting for factors like age, alcohol consumption, smoking, and BMI, each 100 kcal expended per day leads to a 2.09 mg/dl increase in HDL-C.
• Higher intensity activity correlates with lower total cholesterol.
• Aerobic exercise's impact on blood lipids may be unrelated to changes in cardiovascular fitness.
• Lipid profile is related to energy expenditure and body fat reduction.

Biological Plausibility: Reduced Hypertension Risk

• Moderate-intensity physical activity prevents and treats mild hypertension by both epidemiological observations and experiments.

Hypertension and Cardiac Output

• Hypertension is measured as the force applied to artery walls, with a mathematical relationship to cardiac output and total peripheral resistance (TPR).
• Normotensive individuals show no change in resting cardiac output with exercise training.
• Hypertensive individuals may have a slight reduction in resting cardiac output due to reduced plasma volume.

Total Peripheral Resistance (TPR)

• Exercise reduces TPR by 27% and plasma norepinephrine by 20% immediately, suggesting reduced SNS activity.

Aerobics Center Longitudinal Study (ACLS)

• ACLS studied 4800 men and 1200 women between 20-65 years old.
• Subjects underwent a medical exam between 1970 and 1981 and were classified as either low fit or high fit based on treadmill time.

Harvard Alumni Study Results

• A study of 15,000 male Harvard graduates determined that those who reported less than 2000 kcal of activity per week had a 30% greater risk of developing hypertension.
• Men who did not report participation in vigorous activity had a 35% greater chance of developing HTN.

University of Pennsylvania Alumni Study

• A study of University of Pennsylvania alumni showed a 30% higher age-adjusted risk of developing hypertension for those spending less than 5 hours per week playing sports.
• Further analysis showed that vigorous activity during middle age reduced hypertension, irrespective of weight or parental history.

Physical Activity and Hypertension

• Based on 25 clinical studies, exercise lowers both systolic and diastolic blood pressure for people with mild hypertension.

Lifestyle Physical Activity

• It is possible to incrementally incorporate physical activity to reduce blood pressure.

Insulin

• Insulin lowers blood glucose by increasing it's uptake into cells.
• Direct relationship between plasma insulin and hypertension.
• Insulin increases SNS activity and promotes sodium re-absorption.

Stress Reactivity

• Higher fitness levels are associated with lower heart rate and blood pressure responses to stressful events.
• Decreases in HR and BP result in lower myocardial oxygen demand.

Morphological Changes

• When the heart experiences exercise, it undergoes morphological changes, including increased left ventricular wall thickness and volume.
• Exercise induces a physiological proliferation of vessels in the heart.