Protein is a popular topic among both casual and competitive athletes, many of whom are confused about how much they need, when they should eat it, and the best kinds to choose.
Just as children have high protein needs during growth periods (0.6 grams per pound or 1.3 grams per kilogram), athletes also have requirements higher than the Recommended Daily Allowance (0.4 grams per pound or 0.8 grams per kilogram) when building muscles: 0.55 grams per pound (or 1.2 grams per kilogram) for endurance athletes, and 0.75 grams per pound (or 1.7 grams per kilogram) for strength athletes. These protein recommendations assume the athlete is consuming adequate energy from carbohydrate and fat. Athletes who restrict their food intake end up using some protein for fuel, thus they need a higher protein intake. Most athletes consume ~0.7 grams per pound (1.6 grams per kilogram per day), so they easily meet the protein recommendations without supplements.
The best way to stimulate muscular growth is to lift weights or do other forms of resistance exercise. To support muscular development after hard lifting, all athletes need to consume high quality protein (with all the essential amino acids) in close proximity to their training. High quality proteins include milk products, poultry, eggs, fish, lean beef, all meats, and soy protein.