Isotonic drinks and long-distance runners
The hypothesis that long-distance runners will improve their performance after drinking isotonic drinks is proven to be true.
Sports drinks should be taken after long hours of strenuous training, which lasts for more than 1 hour. Drinking sports drinks helps to replenish water, minerals and carbohydrates that are lost during the exercise. However, drinking too many isotonic drinks especially if you aren't exercising, will lead to other health problems, such as weight gain.
This science fair project can also be repeated with other sports like swimming, cycling and triathlons.
This experiment can also be repeated using different brands of isotonic drinks (eg. Gatorate vs 100 Plus).
What about regular soda? Will consuming regular soda lead to similar results? What about coffee or other beverages that contain caffeine?
Sports drinks - http://www.atg.wa.gov/teenconsumer/health_and_safety/sports_drinks.htm
Running out of steam - http://www.alive.com/4545a12a2.php?subject_bread_cramb=956