Cardiovascular Variables and Exercise

Cardiovascular Variables

Stroke Volume (SV)

• Defined as the amount of blood ejected from the left ventricle per contraction.
• SV Calculation: End Diastolic Volume (EDV) - End Systolic Volume (ESV).
• EDV: Volume in the ventricle at the end of diastole (relaxation phase).
• ESV: Volume remaining in the ventricle at the end of systole (contraction phase).

Cardiac Output (Q)

• Volume of blood pumped by the left ventricle per minute.
• Formula: Q = SV * Heart Rate (HR).
• Typically around 5 liters/min at rest.
• Unit: Liters per minute (L/min).

Ejection Fraction (EF)

• Percentage of EDV ejected per contraction.
• EF Calculation: SV / EDV.
• Normal Range: 50-70%.
• Heart Failure: EF < 40%.

Blood Flow Mechanisms

Venous Return

• Factors:Breathing, Muscle Pumps, One-Way Valves.
• Frank-Starling Mechanism: Increased EDV stretches cardiac tissue, increasing contractility (strength of contraction).
• Preload: Amount of blood filling the chamber before contraction.
• Afterload: Pressure the heart must overcome to eject blood.

Blood Pressure (BP)

• Systolic BP (SBP): Pressure during ventricular contraction.
• Diastolic BP (DBP): Pressure during ventricular relaxation.
• Mean Arterial Pressure (MAP): Average pressure during the cardiac cycle.
  • Formula: MAP = (SBP + 2 * DBP) / 3.

Hypertension

• Stages: Stage 1 (130-139) / (80-89), Stage 2 (≥140)/ (≥90)
• Hypertension Crisis: >180/ >120
• Causes: High sodium intake, lack of physical activity, alcohol consumption.

Hypotension

• Low blood pressure.
• Concern: <70 SBP is an absolute contraindication to exercise.

Exercise Physiology

Heart Rate (HR)

• Resting HR: 60-80 bpm; trained athletes may have 30-40 bpm.
• Tachycardia: HR >100 bpm.
• Bradycardia: HR <60 bpm.
• Maximum HR (HRmax): 220 - age or Tanaka Formula (208 - 0.7 * age).

Stroke Volume with Exercise

• Increases with exercise intensity up to 40-60% of max capacity.
• Plateaus as HR increases.

Cardiac Output with Exercise

• Increases with intensity.
• Factors: Increased HR and SV up to 60% of max capacity.
• Cardiovascular Drift: HR increases disproportionately as SV plateaus during prolonged exercise.

Blood Distribution in Exercise

• Vasodilation: Increases blood flow to active tissues.
• Vasoconstriction: Reduces blood flow to inactive areas.

Blood Plasma Volume

• Decreases initially due to sweating.
• Effect: Increased blood viscosity.

Vascular Dynamics

Regulation of Blood Pressure

• Resistance: Length of the blood vessel, blood viscosity, and radius of vessel.
• Ohm’s Law: Blood Flow (Q) = Pressure Difference / Resistance.

Capillaries and Exercise

• Pressure drops significantly at arterioles to prep blood for capillary exchange.

Adaptations to Training

Vascular Remodeling

• Arteries and arterioles enlarge, improve dilation capacity.
• Collateral Circulation: Formation of new blood vessels to bypass occlusions.

Effects of Regular Exercise

• Heart Rate: Decreased resting HR, increased efficiency.
• Stroke Volume: Higher SV at rest and during exercise.
• BP: Generally lower BP at rest.

VO2 and a-vO2 Difference

• a-vO2 Difference: O2 content difference between arteries and veins, indicates oxygen extraction.
• VO2 Calculation: VO2 = Cardiac Output (Q) * a-vO2 Diff.
• Fick’s Equation: VO2 = HR * SV * a-vO2 Difference.

Central Command Theory

• Initial Heart Rate Regulation: Higher brain centers initiate HR change.
• Fine-tuning: Feedback from peripheral receptors adjusts HR to meet demands.

Miscellaneous Topics

Varicose Veins

• Causes: Faulty one-way valves leading to backflow and vein distension.
• Recommendations: Avoid straining exercises, emphasize cooldown.

Key Blood Pressure Influences

• Factors like blood volume, heart rate, stroke volume, blood viscosity, and peripheral resistance affect BP.

Assignment: Research how five factors affect blood pressure and write descriptions.