Chlorophyll, the dark, green pigment that makes greens green, is essentially the blood of plants and what they use to turn sunlight into carbohydrates during photosynthesis. For humans, consuming chlorophyll provides blood-building properties that are key to endurance athletes like cyclists. For one, it enables our blood to carry more oxygen throughout our system without needing an increase in blood volume, which means we'll be able to ride at a higher intensity, with no extra cardio output. That's good.
Of course this directly enhances endurance in sports such as cycling. One big (four-cup) salad a day is sufficient, using any source of greens: spinach, kale, arugula, romaine lettuce, and dandelion greens.