Cardiac Physiology and Effects of Exercise on Heart Health lecture 3

Effects of Sedentary Behaviour on Cardiovascular Health

• Connection to Health Risks

  • Individuals with sedentary jobs have a 50% higher risk of coronary heart disease (CHD) compared to those with physical jobs (Morris et al, 1953).

  • There is a likely causal relationship between physical inactivity and CHD.

• Risk Factors of a Sedentary Lifestyle

  • Hypertension: Systolic blood pressure > 150 mmHg (compared to 120 mmHg).

  • High Cholesterol: Levels above 268 mg/dl.

  • Smoking: More than 20 cigarettes a day.

Benefits of Exercise on Health

• Regular exercise promotes:

  • Metabolic Wellness: Enhances overall metabolic function.

  • Mental Health Improvements: Reduces symptoms of anxiety and depression.

  • Musculoskeletal Function: Builds and maintains muscle strength and endurance.

  • Increased Lifespan: Associated with a longer, healthier life.

• Physical Activity Measurement:

  • Measured by age, gender, and ethnicity variables in the UK government guidelines.

  • Moderate Activity: Raises breathing rate; equivalent to vigorous activity for exercise tally (1 min vigorous = 2 min moderate).

Exercise and Cardiac Anatomy

• Acute vs. Chronic Exercise Effects:

  • Acute Exercise: Activates the sympathetic nervous system (SNS), leading to short-term responses (e.g., increased heart rate, adjusted blood volume).

  • Chronic Exercise: Results in long-term adaptations, such as:

  • Improved maximal oxygen uptake ($ ext{VO}_2 ext{max}$).

  • Decreased resting heart rate.

  • Decreased blood pressure.

  • Increased muscle mass.

• Cardiac Hypertrophy: Adaptation of the heart muscle in response to exercise, either physiological (healthy) or pathological (diseased).

  • Types of Hypertrophy:

  • Eccentric Hypertrophy: Proportional increase in chamber size and wall thickness; generally healthy.

  • Concentric Hypertrophy: Disproportionate increase in wall thickness; associated with poorer outcomes in heart disease.

Heart Rate Regulation During Exercise

• Intrinsic Rhythmicity: The heart's natural rate is approximately 70-100 beats per minute (bpm) without stimulation.

• Extrinsic Control: Nerve signals and hormones can influence the heart rate, potentially accelerating it to approximately 220 bpm during intense exercise.

Blood Flow Dynamics During Exercise

• Importance of Cardiovascular and Pulmonary Integration:

  • Allows for increased oxygen demand and improved blood flow.

• Adjustments in Blood Flow:

  • Redistribution occurs based on activity demands, prioritizing muscles during exercise.

  • Cardiac Output: Defined as:
    ext{Cardiac Output} = ext{Stroke Volume} imes ext{Heart Rate}

• Effects on Blood Pressure: Alterations include:

  • Changes in systolic blood pressure (BPS) and diastolic blood pressure (BPD).

  • Ejection fraction increases with improved exercise capacity.

Physiological Changes Due to Exercise Training

• Blood Changes During Exercise:

  • Decreased plasma volume leads to higher concentration of red blood cells, enhancing oxygen delivery.

  • Blood pH drops due to increased lactate levels, shifting the oxygen-hemoglobin dissociation curve.

• Training Adaptations:

  • Overall blood volume increases with regular training, improving oxygen-carrying capacity and athletic performance.

Concept of Cardiac "Psychiatry"

• Physical Activity as a Preventive Measure: Encourages maintenance of physical strength, balance, and motor skills.

• Impact on Wellbeing: Regular exercise fosters mental health improvements, self-esteem, cognitive function, and social skills development, also influencing employment opportunities.

Learning Outcomes from the Session

• Understanding the effects of sedentary behaviour on cardiovascular health.

• Recognizing the impact of exercise on cardiac anatomy, heart rate regulation, blood flow, and blood pressure.

• Awareness of the concept of ‘cardiac psychiatry’ and its implications for holistic health.

Contents

1. Connection to Health Risks

2. Risk Factors of a Sedentary Lifestyle

3. Benefits of Exercise on Health

4. Exercise and Cardiac Anatomy

5. Heart Rate Regulation During Exercise

6. Blood Flow Dynamics During Exercise

7. Physiological Changes Due to Exercise Training

8. Concept of Cardiac "Psychiatry"

9. Learning Outcomes from the Session