Final answer:
Recombinant erythropoietin improves endurance performances such as the 10 km run performance by increasing the amount of oxygen delivered to the muscles.
Step-by-step explanation:
Recombinant erythropoietin would be expected to improve endurance performances such as the 10 km run performance. Erythropoietin stimulates the production of red blood cells, which increases the amount of oxygen delivered to the muscles. This helps improve aerobic respiration and allows athletes to maintain higher levels of performance for longer periods of time.