How to eat before, during and after ready-set-go

March 9th, 2011

THE HALF-MARATHON: DO YOU NEED THE CARBS?

As mentioned last week, stored carbohydrate, known as glycogen, is one of the limiting factors for any endurance sport. Roughly speaking, the average person can store about a pound of glycogen in their muscle tissue, or enough to sustain about two hours of running, cycling, or swimming, or other endurance sport.

Since the half-marathon takes an average of about two hours to complete, running out of glycogen can start to be a concern. For those who train on a diet that includes a mix of whole grains, fruits, starchy vegetables, and beans and legumes, glycogen depletion is probably not a major issue, but if you gravitate to a lower-carb lifestyle, you might find yourself “hitting the wall” (or bonking) during your longer runs or on race day. Once you run out of stored glycogen, your tired muscles are forced your muscles to switch to other fuel sources (mostly fats) to generate energy, but since this process is not as quick or efficient as burning carbohydrates, you inevitably find yourself running like someone who has had a refrigerator delicately placed on their back.

Wall-hitting types can push it back by adding more carbohydrates to their usual diet, which helps to top up glycogen stores for both training and racing (note that, as you become better trained, you will rely less on carbohydrates and more on slower-burning fats as fuel, so good training is also important for effective racing). Another alternative is to have a carbohydrate-based meal or snack between 1 and 3 hours before you start your run or race. At the very least, this will ensure that your blood sugar is still elevated for the start of your run, allowing your muscles to use the sugar from your bloodstream first, before tapping into the fuel in your muscle. Simple pre-run snack ideas that shouldn’t upset your stomach can include ripe bananas, whole grain pita or English muffin, or lower fibre cereals or granola bars.

In terms of hydration, there is a good chance that you can become dehydrated during a half-marathon, so getting accustomed to grabbing water or a sports drink, even if it is just at a fountain along your usual route, is helpful. While sports drinks aren’t crucial for the half-marathon (unless you are already running low on glycogen), interesting new evidence suggests that taking a few sips, or even just rinsing your mouth with a sports drink, can actually result in improved performance. It seems that the sensation of the carbohydrates in your mouth triggers the body to pick it up a notch, so to speak, as though the fuel had actually been consumed.

THE MARATHON: TIME FOR A PLAN

If the half-marathon is a “maybe … maybe not” kind of race when it comes to the potential for dehydration and hitting the wall, the marathon is the distance that can humble even the most well-trained runner.

While maintaining a carb-rich diet is important for those training for the marathon, other issues such as recovery become increasingly crucial, especially if you are training on back-to-back days. When possible, plan to eat a snack that includes both protein and carbohydrates, ideally in the first half-hour after your long runs or cross-training sessions, to help to repair muscle damage and replenish glycogen. Chocolate milk is a popular option (it is higher in sugar than most beverages, but research suggests that can help speed recovery), but fruit-flavoured yogurt, a protein shake with banana and berries, or even a sandwich made with lean meat is a good option. In general, watch your fat intake during recovery: it can slow digestion and recovery, so you’re probably best to save foods like peanut butter, nuts, or cheese for a little later on.

Since even the most glycogen-replete athlete is bound to run out of carbs during a marathon, you’ll want to make a plan to consume between 30 to 60 grams of carbohydrates per hour of your run or race, starting at the latest by the 90-minute mark or thereabouts. Popular choices include sports drinks, gels, or gummies, but low-fibre carbohydrate foods such as ripe bananas, pretzels, granola bars, baby cookies, and fig bars are all reasonable options that are easy to digest and shouldn’t cause stomach upset if eaten in small amounts. Note, however, that concentrated sugars such as gels (which provide about 25 grams of carbohydrates in a tiny package) can upset your stomach if they aren’t taken with enough fluid. Ideally, each gel should be consumed with about 2 cups (500 ml) of water, which can help to dilute the sugar enough to be absorbed with maximal efficiency (most sports drinks are formulated to this optimal ratio of 4 to 7 grams of sugar per 100 ml of fluid).

Jennifer Sygo is a dietitian in private practice at Cleveland Clinic Canada (clevelandclinic.ca), which offers executive physicals, prevention and wellness counselling and personal health care management in Toronto.

Available at The National Post:  http://www.nationalpost.com/life/before+during+after+ready/4398501/story.html