"Be tough." "Bring it." "No excuses." With macho slogans like these printed on the bottles, there's no doubt that the makers of the sports drink Gatorade want to link their products with strong athletic performance. And we're obviously happy to believe them. Their product is the leading brand in a market reportedly worth $4 billion in recent years.

There is some good science behind sports drinks. According to the American College of Sports Medicine, if you're exercising for longer than 45 minutes, or doing particularly intensive exercise, drinks containing carbohydrates and electrolytes can enhance your performance. Adding carbohydrates to a drink helps your body absorb it faster than pure water. Around 3 to 6 percent carbohydrate seems best.

In the past few years, there's been interest in the idea of using skim milk as an alternative to sports drinks. Naturally occurring sugar in milk, called lactose, gives it a similar concentration of carbohydrates to some leading sports drinks. Milk also contains electrolytes in the form of sodium and potassium.

Researchers from James Madison University have now done a study in college soccer players, and found that low-fat chocolate milk was no different to a high-carbohydrate sports drink when it came to athletic performance and recovery. Athletes drinking milk also had lower amounts of a chemical marker in their blood that indicated muscle breakdown, possibly because the protein in milk helped rebuild their muscles.