Final answer:
Caffeine can improve endurance performance by increasing energy available during exercise. It delays muscle and central fatigue, increases power output, and improves cycling and running performance.
Step-by-step explanation:
A proposed explanation as to why caffeine may be able to improve endurance performance is that it can increase energy available during exercise. Caffeine is considered a proven ergogenic aid that can improve athletic performance, especially in endurance sports. It can delay the onset of muscle fatigue and central fatigue, increase power output, and improve cycling and running time trial performance. Additionally, caffeine ingestion prior to aerobic exercise can increase fat oxidation, particularly in individuals with low physical fitness.