Originally Answered: How do track players get such a flat stomach?
Generally, when you are in a sport you are encouraged to eat healthily. That means lots of water and gatorade so you don't get dehydrated, healthy food. No more of that sugary, greasy stuff! That's a rarity. Keep your eyes on the greens. That's only the key to help you gain that stomach, without it the task would be much more difficult.
While working out for track, you do many different things. You run, a lot. Warm up runs; slow, average, fast. (jogging, distance, and sprinting.) You also work on your strength, mainly in your legs. To do this, check out my list of things that I do;
WALL SQUAT. A wall squat is an exercise where you lean against a wall in a sitting down position. Sit against the wall as if you were going to sit on a bench, but keep your back straight. (along the wall) Stay in this position for two minutes. If you haven't done this before, start with one minute. These squats target the muscles of the back, abddomen, and thigh.
MOUNTAIN CLIMBERS. A mountain climber is an exercise where you get in the push-up position and alternate legs, as if you were when running. You bring one leg up to your chest, then switch to the other. Do this quickly for a minute, or more if you can tolerate it. This is a good exercise if you don't have a lot of time on your hands and want to work on your legs.
PYLOMETRIC SQUATS. Stand with your feet shoulder-width apart. Then, squat down, bending your knees to 90 degrees. And after that, you'll jump up and land softly again in the squat position. Use the strength in your legs to jump up with such excitement. Make sure you land softly, knees bent.
LUNGES. Stand with your feet hip-width apart and then lunge forward with your left leg. Come back up, and straight your left leg. You right leg should not have touched the floor when you did that lunge.
I also do many other exercises, such as balances. You should research more on this topic. For the upper body, push ups are good. So are sit ups and superman.
I would give you more examples, but quite frankly I have to get ready for an extra practice. I've actually got a meet in a few days, so we want to practice as much as possible.
P.S.: Don't push yourself too hard! Do what you can, and slowly add on to it. You'll be fit in no time. Have fun. :)