Part 4 Effects of Acute Exercise on Cardiac output & Blood Pressure ASC

Cardiovascular System: Effects of Acute Exercise on Cardiac Output & Blood Pressure

Definition of Cardiac Output

  • Cardiac Output (Q): Amount of blood pumped by each side of the heart in one minute (L∙min−1).

  • Components:

    • Heart Rate (HR): Rate of heartbeats per minute.

    • Stroke Volume (SV): Volume of blood pumped per heartbeat.

  • Formula: Q = HR (bpm) × SV (mL).

Effects of Acute Exercise on Cardiac Output

  • Increase in Q: Higher exercise intensity leads to increased cardiac output due to enhanced venous return and increased heart rate/stroke volume.

  • Physiological Responses: Increased sympathetic stimulation and muscle metabolism lead to higher Q during exercise.

Effect of Exercise Intensity on Cardiac Output

  • Generally, as intensity rises, Q rises. Influencing factors include muscle oxygen utilization and heart pumping capacity.

Definition of Stroke Volume

  • Stroke Volume (SV): Volume of blood ejected from the heart per beat (mL).

  • Components:

    • End-Diastolic Volume (EDV): Blood volume in ventricles at end of filling.

    • End-Systolic Volume (ESV): Blood volume remaining after contraction.

  • Formula: SV = EDV - ESV.

Effects of Acute Exercise on Stroke Volume

  • SV notably increases during low-intensity exercise (up to 40-50% VO2 max) but may plateau at higher intensities.

Anticipatory Heart Rate Response

  • Before Exercise: Heart rate rises due to sympathetic (fight/flight) stimulation and reduced parasympathetic ( rest and digest) activity.

Heart Rate Response During Exercise

  • Increases significantly due to: increased sympathetic activation and peripheral receptor signaling for oxygen demand.

Components of Blood Pressure

  • Blood Pressure (BP): Force of blood against arteries (mmHg).

    • Systolic Pressure: Peak pressure during contraction.

    • Diastolic Pressure: Lowest pressure during relaxation.

    • Total Peripheral Resistance (TPR): Resistance to blood flow.

Blood Pressure Response to Acute Exercise

  • Systolic BP rises with cardiac output increase; diastolic BP remains constant or slightly decreases due to blood flow redistribution to active muscles.

Factors Affecting Blood Pressure

  • Influences include age, weight, time of day, and acute exercise effects.

Gender and Training Effects

  • Typical cardiac output: men ~5 L/min, women ~4.5 L/min. Trained individuals show higher stroke volumes due to greater blood volume and cardiac efficiency. Women generally have higher resting heart rates.

Key Mechanisms:

  • Increased sympathetic activity and peripheral receptors activate while parasympathetic functions decrease during exercise to boost oxygen delivery.