Analyse how different intensity levels of exercise affect the heart rate response in a trained versus untrained individual. (8 marks)
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Sample Answer
- During a progressive exercise test, heart rate, cardiac output and stroke volume interact to meet the increasing metabolic demands of the working muscles.
- Early stages (low intensity)
- Heart rate increases linearly from resting levels (60-80 bpm) to approximately 110-130 bpm.
- Cardiac output increases primarily due to increased stroke volume, which may increase from 70-80 ml/beat at rest to 100-120 ml/beat.
- Moderate intensity
- Heart rate continues to increase linearly (130-160 bpm) and stroke volume may reach its maximum capacity (120-150 ml/beat in average individuals).
- The continued increase in cardiac output at this stage is primarily due to increasing heart rate.
- High-intensity exercise (80-90% of maximum heart rate)
- Stroke volume typically plateaus while heart rate continues to increase, approaching maximum levels (170-200 bpm depending on age).
- Cardiac output continues to rise due to increasing heart rate despite stable stroke volume.
- Very high intensity exercise
- Less time is available for ventricular filling between beats, which may cause a slight decrease in stroke volume.
- The heart compensates by further increasing heart rate to maintain or increase cardiac output.
- The relationship between these variables demonstrates an effective compensatory mechanism that allows the cardiovascular system to meet metabolic demands efficiently.
- In untrained individuals, heart rate increases more rapidly and stroke volume plateaus at a lower level
- In trained individuals, require higher heart rates to achieve the same cardiac output.
- The interrelationship between heart rate, cardiac output and stroke volume demonstrates how the cardiovascular system adapts during exercise, with cardiac output increasing through changes in both heart rate and stroke volume to meet the body’s changing oxygen demands.
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Sample Answer
- During a progressive exercise test, heart rate, cardiac output and stroke volume interact to meet the increasing metabolic demands of the working muscles.
- Early stages (low intensity)
- Heart rate increases linearly from resting levels (60-80 bpm) to approximately 110-130 bpm.
- Cardiac output increases primarily due to increased stroke volume, which may increase from 70-80 ml/beat at rest to 100-120 ml/beat.
- Moderate intensity
- Heart rate continues to increase linearly (130-160 bpm) and stroke volume may reach its maximum capacity (120-150 ml/beat in average individuals).
- The continued increase in cardiac output at this stage is primarily due to increasing heart rate.
- High-intensity exercise (80-90% of maximum heart rate)
- Stroke volume typically plateaus while heart rate continues to increase, approaching maximum levels (170-200 bpm depending on age).
- Cardiac output continues to rise due to increasing heart rate despite stable stroke volume.
- Very high intensity exercise
- Less time is available for ventricular filling between beats, which may cause a slight decrease in stroke volume.
- The heart compensates by further increasing heart rate to maintain or increase cardiac output.
- The relationship between these variables demonstrates an effective compensatory mechanism that allows the cardiovascular system to meet metabolic demands efficiently.
- In untrained individuals, heart rate increases more rapidly and stroke volume plateaus at a lower level
- In trained individuals, require higher heart rates to achieve the same cardiac output.
- The interrelationship between heart rate, cardiac output and stroke volume demonstrates how the cardiovascular system adapts during exercise, with cardiac output increasing through changes in both heart rate and stroke volume to meet the body’s changing oxygen demands.