Want to know the secret to raising a champ?

It's all about having the right diet with essential micronutrients, says a study in the Journal of Applied Physiology. Getting enough of vitamins A and D, iron and the antioxidant beta-carotene can help boost a growing kid's cardio performance and muscle strength.

Make it a habit: Exercising and eating well increase fitness, says lead researcher Dr. Luis Gracia-Marco. Fuel your kid's success with leafy greens and vegetables like spinach, carrots, sweet potatoes and bell peppers.