How to eat and drink to maintain your energy on race day

What you put in your body during exercise can mean the difference between a winning performance and one that leaves you bonking toward the finish. Here's how to eat and drink to avoid hitting the wall.

Your Workout: Weight-training or light cardio
What You Need: Nothing but water
Why: "Most people just need water if they are doing moderate exercise for less than one hour," says Tara Gidus, R.D., an Orlando-based sports dietitian and spokesperson for the American Dietetic Association. Research has shown there is little benefit to consuming calories during moderate-intensity exercise that characterize most gym workouts. And it's no benefit to your waistline if you're consuming more calories from an energy bar than what you are expending. One exception to the rule, says Gidus, would be if you are exercising first thing in the morning on an empty stomach.

Your Workout: A run or bicycle ride longer than an hour
What You Need: Carbs and fluids
Why: Research demonstrates a performance benefit to consuming carbohydrates during continuous exercise such as marathons or Olympic distance triathlons that last longer than one hour. The reason for this boost? The consumption of carbohydrates raises blood glucose levels, and working muscles will use this glucose to generate the energy needed for muscle contraction. This in turn helps spare the glycogen stored in your muscles and liver, so it can be called upon later in a race when you need an extra push to the finish line. "The human body only has about 2,000 calories worth of glycogen storage which will be used up during long duration exercise if carbohydrates are not consumed," Gidus says. Sport drinks, gels and carbohydrate-focused energy bars are good options for a supply of carbohydrates (sugars) during exercise. Sport Beans (sportbeans.com) are another winning pick. "I recommend athletes aim to consume 30 to 60 grams of quick digesting carbohydrates for each hour of activity," advises Gidus. The other essential ingredient for a successful race is fluids.

Your Workout: Ultra-endurance race
What you need: Lots of calories and fluids
Why: While nutrition guidelines are similar to that of the shorter athletic events mentioned above, there are few extra concerns. The necessity of increased calorie intake means that protein and fat consumption can become useful. The race is long enough that you will be able to digest these two macronutrients. Also, the high intake of plain water for a long period of time can result in hyponatremia -- a dangerous drop in blood sodium levels. Make sure to consume fluids or foods that contain sodium throughout the race. Gatorade Endurance Formula (itsonthecourse.com) adds extra sodium to the classic sports drink.

Matthew Kadey is a Toronto-based dietitian and free-lance writer (www.mattkadey.com)