Explain the relationship between stroke volume, heart rate and cardiac output during an aerobic training session. (6 marks)
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Sample Answer
- Cardiac output functions through the interaction of stroke volume and heart rate. The formula CO = SV × HR demonstrates this direct relationship.
- At exercise onset, both components increase immediately. The plateau happens because working muscles demand more oxygen for energy production.
- Stroke volume rises from resting values to near-maximum levels quickly. As a result, cardiac output increases substantially within the first minutes of exercise.
- However, stroke volume plateaus at moderate intensity while heart rate continues rising. This happens because ventricular filling time decreases at higher heart rates.
- Therefore, further cardiac output increases depend primarily on heart rate. The shift occurs when stroke volume reaches its maximum capacity at moderate intensities.
- During sustained aerobic exercise, heart rate becomes the main contributor. Consequently, cardiac output can continue increasing despite stable stroke volume.
- The recovery phase shows different response patterns. Heart rate drops rapidly while stroke volume decreases more gradually.
- These differences occur because neural control affects heart rate immediately. Stroke volume changes depend on venous return and contractility adjustments.
- Overall, the relationship between components enables flexible cardiac output regulation. Such coordination allows the cardiovascular system to meet varying oxygen demands throughout aerobic training.
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Sample Answer
- Cardiac output functions through the interaction of stroke volume and heart rate. The formula CO = SV × HR demonstrates this direct relationship.
- At exercise onset, both components increase immediately. The plateau happens because working muscles demand more oxygen for energy production.
- Stroke volume rises from resting values to near-maximum levels quickly. As a result, cardiac output increases substantially within the first minutes of exercise.
- However, stroke volume plateaus at moderate intensity while heart rate continues rising. This happens because ventricular filling time decreases at higher heart rates.
- Therefore, further cardiac output increases depend primarily on heart rate. The shift occurs when stroke volume reaches its maximum capacity at moderate intensities.
- During sustained aerobic exercise, heart rate becomes the main contributor. Consequently, cardiac output can continue increasing despite stable stroke volume.
- The recovery phase shows different response patterns. Heart rate drops rapidly while stroke volume decreases more gradually.
- These differences occur because neural control affects heart rate immediately. Stroke volume changes depend on venous return and contractility adjustments.
- Overall, the relationship between components enables flexible cardiac output regulation. Such coordination allows the cardiovascular system to meet varying oxygen demands throughout aerobic training.