Analyse the relationship between cardiac output, heart rate and stroke volume as immediate physiological responses to a 30-minute continuous aerobic training session. (6 marks)
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Sample Answer
Cardiac output relationship to heart rate and stroke volume:
- Cardiac output = Heart rate × Stroke volume
- All three increase immediately at the onset of exercise
Initial response (first few minutes):
- Heart rate increases rapidly due to nervous system stimulation
- Stroke volume increases due to increased venous return from muscle contractions
- These combined changes result in rapid increase in cardiac output
Mid-session response:
- Heart rate may continue to increase gradually
- Stroke volume typically stabilises after initial increase
- Cardiac output reaches a relatively steady state appropriate for the exercise intensity
Physiological mechanisms:
- Increased heart rate results from decreased parasympathetic and increased sympathetic stimulation
- Increased stroke volume results from greater ventricular filling and stronger heart contractions
- These adaptations ensure sufficient blood flow to meet the oxygen demands of working muscles
Interrelationship
- The relationship between these variables ensures the body can maintain the required exercise intensity throughout the training session
Show Worked Solution
Sample Answer
Cardiac output relationship to heart rate and stroke volume:
- Cardiac output = Heart rate × Stroke volume
- All three increase immediately at the onset of exercise
Initial response (first few minutes):
- Heart rate increases rapidly due to nervous system stimulation
- Stroke volume increases due to increased venous return from muscle contractions
- These combined changes result in rapid increase in cardiac output
Mid-session response:
- Heart rate may continue to increase gradually
- Stroke volume typically stabilises after initial increase
- Cardiac output reaches a relatively steady state appropriate for the exercise intensity
Physiological mechanisms:
- Increased heart rate results from decreased parasympathetic and increased sympathetic stimulation
- Increased stroke volume results from greater ventricular filling and stronger heart contractions
- These adaptations ensure sufficient blood flow to meet the oxygen demands of working muscles
Interrelationship
- The relationship between these variables ensures the body can maintain the required exercise intensity throughout the training session