Lloyd, Good point. While increasing vegetable intake is the single most important thing anyone can do to increase their health, energy levels, disease prevention and body fat loss, increasing vegetable intake quickly from one day to the next can lead to significant gastrointestinal distress. Increase your vegetable intake slowly over a few weeks to reach your target of 15-25% of your total calories as vegetables (nearly half the volume of your meals, since many vegetables have a lot of air space, such as in salads, for example). Furthermore, the day before an intensive exercise day the total fiber intake should be reduced a bit so that there are no gastrointestinal issues during the exercise. If vegetable intake is being reduced most days of the week to avoid gastrointestinal distress during exercise even after an athlete has had time to adjust to increased fiber intake, there is likely a dehydration issue keeping the athlete from digesting foods well (making the person particularly sensitive to fiber) or the athlete has too many intesive training session per week and is likely headed towards being over-trained. A routine reduction in vegetable intake is a red flag that over-all health is being compromised for the sake of the exercise.
Clyde, It's worth noting that for the first 1-2 weeks in which I increased my vegetable intake it threw my digestive system for a loop. I'd recommend a steady increase for those doing so, rather than suddenly beginning to eat large salads. Also, lots of veggies aren't ideal for the bulk they add to the stomach. I prefer to avoid bulk the day prior and the day of a hard workout or long event.