Athletes who train at high altitudes undergo physiological acclimatisation to compensate for the lower partial pressure of oxygen in the atmosphere. This process involves an increase in the production of red blood cells and haemoglobin.
Scientists investigated the effect of high-altitude training on a group of elite endurance runners. The runners lived and trained at an altitude of 2,400 metres for five weeks. The scientists took blood samples from the runners every week to measure their haemoglobin concentration.
The table shows the results of the investigation.
| Time at high altitude (weeks) | Mean haemoglobin concentration (g⋅dm−3\text{g}\cdot\text{dm}^{-3}g⋅dm−3) |
|---|---|
| 0 | 121 |
| 1 | 129 |
| 2 | 138 |
| 3 | 144 |
| 4 | 148 |
| 5 | 150 |
Describe how to plot a line graph to show the relationship between time at high altitude and mean haemoglobin concentration, specifying which variable goes on each axis.
Name the dependent variable in this investigation.
Explain how the scientists ensured their results were reliable.
Name two biotic (living) factors of the runners that the scientists should have controlled to ensure their results were valid.
An increased haemoglobin concentration improves athletic endurance and delays muscle fatigue. Explain how the physiological changes during acclimatisation lead to these improvements in the runners.
To measure the haemoglobin concentration, the scientists obtained blood samples using a needle and syringe. Explain why they should draw blood from a vein rather than an artery.
