What are the special food requirements for athletic dogs that have to work hard?

Active dogs need better nutrition than an average dog. If a dog spends more than two hours a day in vigorous activities such as frisbee chasing, ball fetching, agility etc, it requires extra calories. The esiest way to find out whether your dog eats enough is to pay attention to its demeanor, appearance and weight. If the animal seems depressed or less energetic than normal (provided that there are no other health issues), you should re-consider its diet. Feed it more of the food you already give it, or switch to foods that are more tightly packed with nutrients. Giving it supplement vitamins and minerals is a good idea too.