| Fuel for the Running Machine |
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A big breakfast on race day will not do. Endurance athletes with serious ambition must commit to developing very specific and reliable fueling and hydration strategies. A carefully crafted fuel and fluid regime is part of your training, period. Although these recommendations are for race day, this is also what you will have practiced and mastered in the months leading up to your race. Race preparation—carbohydrate loading To load or not to load? Carbohydrate loading aims to maximize muscle glycogen stores before an endurance event. Basically, athletes exercising continuously for ninety minutes or more at moderate or high intensity (such as half- and full marathons) will benefit from carbohydrate loading. Intensive research a decade ago by Hawley and colleagues quantified the benefits of carb-loading (compared to fuel during exercise only) and came up with an average of a twenty-per-cent increase in time to exhaustion where athletes run or cycle to fatigue, and a two- to three-per-cent decrease in time to complete a set task such as a time trial or race. This can translate into a five-minute time improvement for someone running a 180-minute marathon. Athletes exercising for shorter periods (less than sixty minutes) or at lower intensities do not need special carbohydrate loading strategies—just be sure to maintain a high day-to-day carbohydrate diet (five to eight grams per kilogram of body weight) and use a sports drink during runs to prevent amino acid oxidation (muscle protein used as fuel), and glycogen depletion that may slow you down or cause premature fatigue.Not to load? Although running low on glycogen and forced abandonment of race pace or worse, “bonking,” is a real risk, some athletes do choose to keep glycogen stores lower and rely on exogenous (eating/drinking) sources of carbohydrate during the race. Why? In order to avoid the weight gain associated with carbo-loading. Guidelines for carbohydrate loadingCarbohydrate loading is not an excuse to gorge on everything in sight. Commitment is required to achieve the necessary high carbohydrate intake.1. Reduce training load over the last three days before competition. You should obtain complete rest twenty-four to thirty-six hours before the race. 2. During these three days, increase carbohydrate intake to eight to twelve grams per kilogram of body weight, or approximately seventy per cent of your calories. Research supports that even a twenty-four-hour rest period with carb-loading is quite comparable to seventy-two hours. 3. Avoid the temptation to indulge in high fat or empty-calorie foods. Remember that carbohydrate is your top priority, lean protein is second, and fat is the remaining small percentage during these three days. 4. Reduce fibre intake to leave room for high-carbohydrate foods and avoid feeling bloated. This is not the time to fill up on salads and steamed veggies. Choose starchy vegetables like yams and potatoes with smaller portions of leafy greens, red peppers, tomatoes, and carrots. 5. Make use of compact carbohydrate sources such as “carbo-load” drinks, dried fruits, juice, and plenty of bread, cereal, rice, and pasta. 6. In the days leading up to the race you should also use salt liberally to help maintain eurhydration (normally hydrated) and to ensure adequate stores of electrolytes. Note to females: The menstrual status of females appears to affect glycogen storage with greater storage occurring during the luteal phase (days fourteen through twenty-eight), which would indicate that exogenous carbohydrate sources during the race may be of greater importance, as storage ability is lessened. Muscle and liver glycogen and fuelingOur main sources of stored carbohydrate are muscle glycogen and liver glycogen. Muscle glycogen is the most readily available energy source for the working muscle. Glycogen content of skeletal muscle is twelve to sixteen grams per kilogram wet weight, equating to a total of about three hundred to six hundred grams of carbohydrate content, with the higher end more common in heavier or more muscular individuals. But this does not necessarily translate into extra fuel availability for these individuals because it is relative to energy requirements, which are higher if you are heavier. Liver glycogen can be thought of as the reservoir that maintains blood glucose levels. This function of the liver occurs at rest and during exercise and becomes a very important contributor to the working muscle at intensities at or above seventy-five-per-cent VO2max. Liver glycogen is also what provides the glucose in the blood that fuels the brain (more on that later). The average adult liver is approximately one and a half kilograms, and can store about one hundred grams of carbohydrate. After an overnight fast, the liver’s carbohydrate stores can be as low as twenty grams, which are only eighty calories of carbohydrate and not enough to back up the muscle glycogen and fuel the brain. Remember what you eat today is what your muscles use for fuel tomorrow. It is impossible to pack your muscles with glycogen in less than twenty-four hours, so be sure to plan ahead. Breakfast will not fuel your race; breakfast is meant to top up liver glycogen and help maintain blood glucose. The majority of your energy, especially in the first hour of the race, is stored muscle glycogen from meals (carbs ingested) in the previous twenty-four hours.Pre-event mealAthletes should consume the last fairly large meal three to five hours before a race. The more time you have, the more you can safely consume. If your race starts early in the morning, you may not have this much time; therefore, it is absolutely critical that you have a large high-carbohydrate meal close to bedtime the night before. However, after an overnight fast your liver glycogen must be replenished, with as much carbohydrate as you can tolerate in the time remaining. Remember, liver glycogen is what your brain relies on and is also a reservoir for working muscles, especially at higher intensities. The pre-event meal aims to top up carbohydrate and fluid levels, leaving your stomach feeling comfortable and you feeling confident. Aim for six hundred to eight hundred kilocalories if you have three to four hours, and three hundred to five hundred kilocalories if you only have two hours. The last forty-five minutes before the race should include one last top-up from a sport drink, or an easily digested carbohydrate such as a small banana or a handful of raisins.These are general guidelines, and some individuals may find different timing more suitable. There are many combinations of foods that are suitable before a race, and it is important to experiment to find the most suitable option for you. This meal must at least provide carbohydrate and fluids and ideally be moderate to low in protein and very low in fat. Foods rich in fibre (greater than five grams per serving), protein (greater than fifteen grams), or fat (greater than three grams per serving) should be avoided in the pre-workout meal since these nutrients cause a diversion of blood, oxygen, and water flow to the stomach to aid in digestion, thereby leading to a “dead-legged” feeling, nausea, or a frantic search for a bathroom. Athletes who suffer from nerves may find a liquid meal such as skim milk (plain or chocolate) and juice (one or two cups of each) easier to tolerate, and this is a safer bet if it’s less than ninety minutes to start time. Ideas for pre-event meals* Toast + banana + honey + sport drink* Cereal + low-fat milk + fruit + juice * Spaghetti + toast + water * Low-fat yogurt + fruit + juice * Oatmeal + skim milk + raisins + brown sugar * Pancakes + syrup + juice/chocolate milk * Bagel + peanut butter + sport drink * Fruit smoothie + cereal bar Start to finish: fuel and hydration strategiesCompetition day often involves a stomach full of butterflies, making the thought of eating and drinking difficult to tackle. Having practiced your competition nutrition strategies during training should leave you at peace with your routine; now is not the time to try something new! And for many, wearing a fuel belt does offer peace of mind. The pros are that you can eat or drink at your own desired intervals, and you can use the sport products (e.g., gels or chews) that you are used to. Plus, you don’t have to be slowed down by crowding at the fueling stations. The cons are the extra weight, which may or may not affect your time and can be determined in your training. It’s also beneficial if you can have a friend on the course route to hand you a drink or gel, which will help you avoid some or all of the aid stations.Carbohydrate intake during the race will improve endurance capacity and performance through a few mechanisms including maintaining blood glucose levels and high carbohydrate oxidation rates, glycogen sparing and central nervous system (CNS) effects. The CNS is often forgotten as a mandatory ally in the race. The brain is highly dependent on glucose as a fuel, and as blood glucose concentrations drop, hypoglycemia may develop, resulting in dizziness, nausea, cold sweat, reduced mental alertness, loss of motor skills, and increased heart rate. Keep in mind that muscle glycogen cannot contribute to blood glucose levels; what is in the muscle, stays there. Therefore, you could hit the wall with fuel still in your muscles, but because it’s too low in your bloodstream. Types and amounts of fuelYour options for fuel are basically sport drinks, gels, chews, and solid bars. If you have carb-loaded the day or night before and had a good breakfast, your muscle and liver glycogen should be full. From a practical point of view, the amount of carbohydrate that needs to be ingested to attain optimal running performance is important. Given that glycogen storage is saturated, the optimal amount is going to the amount that results in maximal exogenous oxidation rates without causing gastrointestinal (GI) problems.Back in 1992, Wagenmakers and colleagues tested the oxidation rates (carbohydrate burning) of varying amounts of carbohydrates such as sixty to 120 to two hundred grams per hour in endurance athletes working at seventy-per-cent VO2max, and the results showed an average oxidation rate of one gram of carbohydrate per minute, with an absolute maximum of 1.1 grams per minute. These values are independent of body weight and negligibly different for intensity. Therefore, runners should ensure a carbohydrate intake of seventy grams per hour for optimal carbohydrate delivery as glycogen stores begin to deplete (forty-five to sixty minutes into a race). Adopting an ingestion rate of seventy grams per hour optimizes exogenous carbohydrate oxidation, and, more than this, does not result in higher oxidation rates but will most likely result in GI discomfort. Sixty to seventy grams of carbohydrate (CHO) per hour can be achieved through the following (note a minimum of thirty grams per hour is recommended during activity over seventy per cent VO2max): 1. 2 Gels* (25 g CHO X 2 = 50g) + 500 ml water + 250 ml sport drink (15 g CHO) = 65 grams CHO 2. 1000-1200 ml of sport drink = 60-72 gram CHO 3. 1 Gel + 750 ml sport drink = 70 grams CHO 4. 1 energy bar (low fat, low protein) 30-35 g CHO + 500 ml sport drink = 60-65 g 5. 5 chews (4 g CHO x 5 = 20 g) + 1 Gel + 300 ml sport drink = 63 grams CHO *Note: It’s important to have water rather than a sports drink with any gel or bar, as the carbohydrate and other nutrient content is more concentrated and therefore requires dilution. Using a variety of carb sources throughout the race is definitely acceptable, but failing to include water with your non-sport drink carbs will most likely result in severe gastric upset. Think of gels or chews and water making a sport drink in your stomach! The water will help lower carb concentration to maximize absorption without GI distress. Water consumption with bars, gels, and chews should be one hundred millilitres for every six to eight grams of carbohydrate. GelsThe most common brands are PowerBar C2@Max Gel, Clif Shots, GU Energy Gel, and GU Roctane. They all provide about twenty-five grams of carbohydrate per packet, with some higher in sodium, which may be beneficial in the heat or if you are a heavy or salty sweater. Choose the one that feels the best on your stomach and gives you the energy boost you need.Some brands contain amino acids, which will not give you a performance advantage, contrary to some advocates of the four-to-one carb-to-protein ratio, which is not relevant when fuel is the priority. Amino acids may also be that one more thing that could upset your stomach, and they won’t make a performance difference. Most brands come with or without caffeine. Caffeine is a known performance enhancer, but it is not desirable for some. Test this in your training to assess whether it’s right for you. The main mechanism by which caffeine exhibits ergogenic effects is by lowering perceived exertion. The last ten kilometres may not feel as strenuous as they would without caffeine. Energy BarsThere are many choices. Be sure to test them in training and be very diligent about keeping them very low fat and fibre, and low protein, but obviously high carb.ChewsClif Shot Bloks, Luna Sport Moons, and Sharkies are all chews that are a great alternative to gels and bars. Usually three to four grams of carbs per chew, like gels or bars, they must be taken with water.Fuel ScheduleThere is no drawback to starting with a sports drink immediately into the race. The worst-case scenario is that you are slightly overcompensating and the liver starts synthesizing more glycogen, and the best case is that you have a pre-emptive strike against hypoglycemia and muscle glycogen depletion. Glycogen can be oxidized at a higher rate when it’s hot, when you are dehydrated, and when exercise intensity increases (e.g., catching the pack or leading a breakaway in a race), so it’s wise not to put total reliance on what you have in reserve, and fuel early.HydrationDue to the confusion regarding hydration status, which ranges from the rarely occurring overhydration potentially causing fatal hyponatremia to the much more common heat exhaustion caused by severe dehydration (discussed here), athletes are often unsure of the best strategy.Dehydration can negatively affect exercise performance, thermoregulation, and cardiovascular response. Although some have recently suggested that thirst is a satisfactory predictor of hydration needs, plenty of evidence indicates that thirst is unreliable, especially in runners and most especially in the heat. Thirst is not a good indicator of body-water requirements or the degree of dehydration. In general, the sensation of thirst is not perceived until a person has lost at least two per cent of body weight through sweating. Runners are particularly vulnerable to dehydration because of the intensity and duration of races, the challenge of drinking while running, and the stresses often imposed by running in conditions of heat stress. Even though experienced runners are typically aware of the consequences of dehydration, when given free access to fluids during exercise they often develop a progressive weight loss, termed “voluntary dehydration.” Research shows that it is not uncommon for individuals to dehydrate by two to five per cent or more of their body weight. A drop of two-per-cent body weight can impair running performance of ten kilometres or more by up to five per cent. Studies by Passe and colleagues in the United States reported that even though the runners studied had easy access to water and sports drinks during a race or on training runs, they replaced on average only about thirty per cent of lost fluids and underestimated their sweat losses by over forty per cent. This conclusion suggests that runners should not depend on self-assessment to maintain adequate hydration, underscores the need for runners to enhance their ability to self-assess sweat losses, and suggests that a predetermined regimen of fluid ingestion is necessary if they wish to maintain more optimal hydration. In addition, dehydration in itself actually decreases gastric empting by up to thirty per cent, making rehydration more difficult. Dehydration speeds up glycogen use as well, adding to the risk of premature fatigue (i.e., both a fuel and fluid issue). Water or Sport Drink?Water is necessary to accompany solid or gel carbohydrates, but a sport drink should be your best friend on race day. However, do realize that you must stick to a six- to eight-per-cent solution. If the carb concentration is too high in the drinks, it will be absorbed more slowly, will likely cause GI distress, and may pull fluid into your gut which will lower your blood volume and dehydrate you.Benefits of Sport Drinks* Increase palatability* Maintain thirst (and therefore promote drinking) * Prevent hyponatremia (low serum sodium concentration due to excessive water intake) * Increase the rate of water uptake (the presence of small amounts of glucose and sodium tend to slightly increase the rate of water absorption compared to pure water) * Increase the retention of fluid * Provide easily digestible and absorbable fuel to maintain blood glucose levels How Much Fluid?Fluid intakes are dependent on individual sweat rate, which is something you should try to assess in training by weighing yourself before and after a long run, preferably in the heat. In the heat some runners may lose two to three litres per hour, and others less than a litre, so you must have a fluid intake regime that matches your sweat losses. In addition, you may need to add a pinch of salt to your sport drink if you are a salty sweater. This requirement is necessary in approximately ten per cent of runners.Pre-RaceAthletes should not refrain from drinking water or carbohydrate-containing fluids during the hours leading up to the race, and it is recommended that approximately four hundred to seven hundred millilitres be ingested during the sixty- to ninety-minute period before the start of the event. This will allow sufficient time for urination of excess fluid, and thus rest-room facilities should be identified. During races lasting longer than one hour (half- or full marathon), athletes often benefit by drinking three hundred to six hundred millilitres of fluid during the fifteen-minute period immediately before the race.During the RaceAgain, this should be individually determined due to the inter-individual variability of sweat rates. The general range is one hundred to two hundred millilitres every fifteen to twenty minutes, with the higher end of the range being more relevant to heavy sweaters or in hot and humid environments. Athletes should be accustomed to consuming fluids at regular intervals (with or without thirst) during training sessions so they do not experience discomfort during the race. Lastly, start early. If you become dehydrated, you can’t catch up. So, pre-hydrate to maximize your performance.Sample Marathon Fuel and Fluid GuideJon is a 170-pound runner who plans to break three hours in his next marathon. Jon estimated his sweat rate and fluid requirement during training by running at race pace in the heat for one hour. He weighed himself nude before and after and found that he lost two pounds. This is equivalent to thirty-two ounces or four cups of water, which is his approximate fluid loss per hour.8:00 A.M. Marathon Start 5:45 A.M. 2 pieces of toast with 2 tbsp peanut butter and 4 tbsp jam, 1 banana, 250 ml of orange juice, 250 ml low fat chocolate milk 7:00 A.M. 500 ml water 7:30 A.M. 500 ml sport drink (Gatorade) 7:45 A.M. 100 ml sport drink 8:00 A.M. Start 8:15 A.M. 200 ml water 8:30 A.M. 300 ml sport drink 8:50 A.M. 1 gel + 250 ml water 9:10 A.M. 300 ml sport drink 9:30 A.M. 1 gel + 300 ml water 9:45 A.M. 350 ml sport drink 10:00 A.M. 1 gel + 300 ml water 10:20 A.M. 300 ml sport drink 10:30 A.M. 200 ml sport drink 10:40 A.M. 200 ml sport drink 10:55 A.M. Finish! About the AuthorNanci S. Guest, M.Sc., RD, C.S.C.S., is a registered dietitian, personal trainer, and strength and conditioning coach, who has owned and operated Power Play: Nutrition, Fitness, Performance since 1995. Nanci holds a Master of Science degree in Nutrition, teaches Sport Nutrition at the University level, and is the Head Sport Nutrition Consultant for the 2010 Winter Olympic Games. She currently provides services in both Toronto and Vancouver. See www.powerplayweb.com."Fuel for the Running Machine" was originally published in IMPACT Magazine's March/April 2009 Running Issue. |
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