# A student is investigating the effect of regular aerobic exercise on the cardiovascular system. The student finds that trained athletes have a lower resting heart rate than non-athletes, yet both groups deliver an adequate supply of oxygen to body tissues at rest. Explain how the heart of a trained athlete is able to maintain adequate oxygen delivery to tissues despite having a lower resting heart rate.

> Pearson Edexcel A-Level Biology A (9BI0) — 1.2 Heart, blood and blood vessels · Explain · 5 marks

> Regular aerobic exercise causes long-term adaptations to the heart. Trained athletes typically have a resting heart rate of around 40–50 beats per minute, compared to approximately 70 beats per minute in a non-athlete.

## Mark scheme (5 marks)

1. The heart pumps blood containing oxygen to the tissues / oxygen is carried in the blood to body cells
2. Cardiac output = heart rate × stroke volume (concept stated or implied)
3. The athlete's heart has a greater stroke volume (more blood pumped per beat) than a non-athlete's heart
4. The greater stroke volume compensates for the lower heart rate, so the same / adequate volume of blood (and therefore oxygen) is delivered per minute
5. Regular exercise causes the heart muscle (myocardium / cardiac muscle) to become stronger / thicker / the heart to become larger, enabling the greater stroke volume

## Key terms

- [heart rate](https://www.gradenine.co.uk/glossary/heart-rate)

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-investigating-the-effect-b8db42a7) · Published by Druglandscape Ltd.