Are you concerned more about physique improvements or performance improvements? I have read from several sources that studies have attempted to correlate body fat percentages to performance improvements and so far none have been successful.
The long and short of it is if you are concerned about improving your performance, don't worry too much about body fat. Bust your ass and your body will more than likely put itself in the most efficient manor that it needs to be in to sustain the stress that you're putting on it.
I would say eat for the activity that you are performing. If I had to take a stab at it, I would say a 1/3 split of macro-nutrients is a safe bet. You'll get enough carbs to fuel the workouts, protein to support your muscles, and fats to help recover from intense training sessions.
That being said, I have absolutely no experience with track, so I'm sure someone else can give you better information.