Cardiovascular system: Variations between trained and untrained individuals.

The idea

Training changes the cardiovascular system, so trained and untrained people differ at rest, during submaximal exercise and during maximal exercise. A trained performer usually has a lower resting heart rate and a larger stroke volume, because the left ventricle fills more and contracts more forcefully. Cardiac output at rest is similar, since a bigger stroke volume balances a lower heart rate. During submaximal work the trained person reaches a given oxygen uptake at a lower heart rate and can sustain it longer. During maximal work the trained person achieves a higher cardiac output and a greater maximum oxygen uptake. Compare values such as resting heart rate, stroke volume and cardiac output to identify the trained individual.

What earns the marks

• Trained individuals typically have a lower resting heart rate than untrained individuals because stroke volume is larger.
• Trained individuals typically have a greater stroke volume at rest and during exercise because the left ventricle fills and contracts more effectively.
• Cardiac output at rest may be similar in trained and untrained individuals because a lower heart rate can offset a larger stroke volume.
• During submaximal exercise, a trained individual reaches a given oxygen uptake at a lower heart rate than an untrained individual.
• During maximal exercise, a trained individual can achieve a higher cardiac output and a higher maximum oxygen uptake.
• Differences are explained by cardiovascular adaptations such as cardiac hypertrophy, increased stroke volume and improved venous return.

Common mistakes and how to put them right

• Assuming trained individuals always have a higher resting cardiac output.

  Put it right: , resting cardiac output is often similar because a lower resting heart rate can balance a larger stroke volume.

• Confusing heart rate with cardiac output.

  Put it right: , cardiac output is the product of heart rate and stroke volume, so a lower heart rate does not automatically mean a lower cardiac output.

• Believing stroke volume is fixed.

  Put it right: , stroke volume increases with training because the heart fills more and contracts more forcefully.

• Thinking untrained individuals have a higher maximum oxygen uptake.

  Put it right: , trained individuals generally achieve a higher maximum oxygen uptake because they can deliver and use more oxygen.

Exam tips

• Compare trained and untrained values directly, naming the variable and the direction of the difference.
• Link each difference to a cardiovascular adaptation, such as a larger stroke volume or a lower resting heart rate.
• Use the relationship cardiac output = heart rate × stroke volume to explain why resting cardiac output can be similar.
• Check whether the question asks about rest, submaximal exercise or maximal exercise, because the pattern of differences changes.