An athlete's red blood cell (RBC) count and haemoglobin levels can adapt to different environmental conditions to optimise oxygen delivery. The table below shows the average RBC count and haemoglobin concentration of an elite runner at sea level and after a 6-week block of high-altitude training at 3000 m3000\text{ m}3000 m.
| Condition | Average RBC Count (×1012 cells/dm3\times 10^{12} \text{ cells/dm}^3×1012 cells/dm3) | Average Haemoglobin Concentration (g/dm3\text{g/dm}^3g/dm3) |
|---|---|---|
| Sea Level | 4.64.64.6 | 140140140 |
| After Altitude Training | 5.25.25.2 | 161161161 |
Calculate the percentage increase in the athlete's average haemoglobin concentration after altitude training compared to their concentration at sea level.
Explain how this increase in haemoglobin concentration helps to prevent muscle fatigue during prolonged exercise.