Eating for Endurance — Nutrition Needs of Power Players
By Jenna A. Bell-Wilson, PhD, RD, LD, and Pamela Nisevich
Today’s Dietitian
Vol. 8 No. 3 P. 38

Athletes need proper carbohydrate and fluid intake in all stages of the game.

As nutrition professionals, we realize the substantial impact nutrition can have on athletic performance. Athletes on all levels continue to seek foods that improve performance as research to support sports nutrition recommendations progresses. The importance of carbohydrate in the diet remains apparent to endurance enthusiasts, but many athletes still need a dietitian’s expertise to guide them through the crucial times—before, during, and after exercise—to avoid bonking, hitting walls, and the pitfalls of inadequate nutrition.

Everyday Endurance Needs
Adequate calories are required during on- and off-season training to maintain muscle mass, ward off illness, support menstrual function, and get the most out of each workout.1 Energy intake can vary depending on where endurance athletes are in their training program but can be estimated by adding the approximate calories used during a session to their normal needs.

Susan Kundrat, MS, RD, LD, sports nutrition consultant for Northwestern University Athletics and author of 101 Sports Nutrition Tips, advises endurance athletes to consume approximately 22 to 25 kilocalories per pound of body weight with 3 to 4 grams per pound of carbohydrate to support training > 90 minutes per day. Kundrat describes this in a practical sense: “[I] develop food plans that reflect the intakes so the athlete knows the servings to get in and the timing.” These recommendations add sports drinks, gels, and recovery shakes to enhance the carbohydrate and calorie content during training and keep the meals nearly the same during the off-season.

Similarly, Julie Upton, MS, RD, writer and sports nutritionist in the San Francisco Bay Area, says endurance athletes need to match their intake and output. Upton warns athletes to reduce intake during their rest weeks and in the off-season. “I see too many [who] overconsume in the off-season and underconsume in the peak of the season,” cautions Upton. “They try to lose weight in race season rather than in the off-season.” Maintaining adequate calories during training weeks is essential to support the demands of the activity and gain results from the hard work invested.

Before Hitting the Pavement
Although exercising on empty seems counterintuitive, many athletes are still unsure what and when to eat prior to a workout. In their defense, preexercise nutrition research has produced varied results from a variety of study designs. That said, in a review by Hargreaves et al, research from the past 20 years supports that carbohydrate ingestion three to four hours prior to exercise enhances muscle glycogen stores.2 In accordance with the position of the American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada, 200 to 300 grams of carbohydrate is recommended three to four hours before activity.1,2

To determine whether more carbohydrate before exercise is better, Cramp et al fed eight trained male mountain bikers a meal of either 1 gram of carbohydrate per kilogram of body weight or 3 grams per kilogram three hours prior to exercise.3 Following a mountain bike performance test assessing power output during intermittent bouts of increased intensity, no differences were found in gastrointestinal response, rating of perceived exertion—a measure of how they feel during activity—and total energy expenditure. Performance was enhanced overall by the high-carbohydrate meal and in the fourth lap but significantly less than the low-carbohydrate meal in the first lap. The initial decline may be attributed to a transient increase in insulin and subsequent drop in blood glucose, leading the researchers to question whether this physiological response plays a role in improving overall performance.3

For those who see sunrise with their sneakers on, early-morning fuel can be a challenge. Schabort et al evaluated the impact of a high-carbohydrate breakfast before prolonged exercise in seven moderately trained male endurance cyclists.4 Subjects were given either no breakfast or 100 grams of carbohydrate from 100 grams of Kellogg’s Cornflakes, 300 milliliters of skim milk, and 0.6 grams of artificial sweetener three hours prior to cycling at 70% of their peak oxygen uptake. Results revealed a significantly greater time to fatigue in the Cornflakes group compared with the overnight fast. The contributing factors could not be determined in this study because no differences in hormonal responses were detected between groups and a lower serum free fatty acid concentration did not hinder performance in the fed group.

To avoid running on empty, Upton advises clients to take in at least 200 calories before a morning workout—and push for 300 to 400 calories if it’s a long one. “Oatmeal or a good whole grain cereal with skim milk is great,” she says. “Many endurance athletes can only tolerate liquids, so they drink a high-carbohydrate drink or nutrition shake.” Upton emphasizes the importance of an individualized plan, since tolerance will vary among athletes, but that “any [food] is better than nothing.”

In addition to carbohydrates, athletes should avoid food items high in fat and fiber-facilitating gastric emptying and minimizing gastrointestinal distress (see “Menu Choices Before, During, and After Exercise” sidebar). It’s not all about the food; fluid plays an integral role as well.

During Activity
By maintaining blood glucose levels and providing carbohydrate to be used as fuel late in the game, replenishing carbohydrate during activity remains unequivocal.5 Research consensus advises 30 to 60 grams of carbohydrate per hour for lasting events.1 In addition to blood glucose preservation, carbohydrate ingestion during activity has been shown to increase time to exhaustion and improve ratings of perceived exertion.6 Utter et al ran 16 marathoners on a treadmill for three hours, providing them with either a carbohydrate beverage or a placebo. Those who drank the carbohydrate beverage showed an increase in carbohydrate use, plasma glucose, and insulin and a lower stress hormone response than those given the placebo, along with lower ratings of perceived exertion.6 Simply, the carbohydrate helped the runners feel better during their exercise.

To put this to practice, Jackie Buell, PhD, L/ATC, director of sports nutrition for The Ohio State University and lecturer for human nutrition, says, “Folks should experiment and figure out what works for them.” Buell suggests that athletes perform a trial run and experiment in a “mock competition environment.” Buell’s recommendations vary, depending on the athlete. “If a sports drink is preferred, fine. Some folks find solids more comfortable, like a bagel or sliced oranges.” Buell emphasizes, “Like many nutritional issues, the athlete has to care enough about it to know what they prefer and plan ahead in order to get it done.”

Other ideas include one to two energy bars, two to three packets of energy gel, or even 3 ounces of Gummi Bears. These snack items can be pinned to shorts, stashed in a fanny pack or bike saddle bag, or hidden ahead of time in a sealed bag by the side of the training course.

Balancing Your Fluids
Fluid and electrolyte balance are critical to optimal exercise performance. Not long ago, it seemed hydration talk among athletes was as simple as: Avoid dehydration by drinking as much as you can. Dehydration was the usual suspect in threatening performance and increasing perceived exertion and heart rate. Dehydration is still a worry, but a newer concern has popped into mainstream sports nutrition: hyponatremia, or low serum sodium levels. Data from the venerated Boston Marathon published in a 2005 issue of The New England Journal of Medicine revealed that of the 488 runners providing blood samples at the finish line, 13% had hyponatremia.7 Correlates with hyponatremia included increased body weight during the marathon (likely due to an increased fluid intake and abnormal retention), long racing time, and those with body mass index extremes.

That said, attention to hyponatremia should not detract from the seriousness of dehydration. With as little as 1% to 2% of body weight lost during activity, performance can suffer, with further decrements leading to severe side effects such as cardiovascular strain, hyperthermia, and altered metabolic and central nervous system function.8 Athletes should attempt to limit body mass losses to less than or equal to 1% to 2% of body mass.8

Chris Jensen, PhD, MPH, of the Gladys Block Research Group at the University of California, Berkeley and expert with the PowerBar Sports Nutrition Advisory Board, states that the most recent hydration recommendations call for an individualized approach. Jensen recommends that athletes determine their sweat rate by measuring their weight before and after a one-hour workout at the intensity they train and/or compete at. “Drinking fluid during the sweat rate test is fine and encouraged,” explains Jensen, “but you need to track how much fluid is consumed.” Jensen says the weight lost, taking into account the fluid consumed, represents the amount of fluid lost as sweat per hour. “Once you know how much fluid you typically lose and need to replace,” advises Jensen, “it’s a matter of coming up with a strategy to drink that volume of fluid each hour.”

To reach your hydration goals, Jensen notes, “Small volumes consumed frequently are tolerated the best, but athletes should experiment during training and find out what drinking pattern works best for them.” Jensen points out that www.PowerBar.com provides a hydration calculator to assist in this process.

Postworkout Needs
After a workout, the body is primed to refuel and replenish. As indicated, fluid replenishment should be part of any athlete’s regimen. In addition, the body is ready to restore glycogen stores, repair muscle damage, and promote protein synthesis—especially immediately following activity.9 Ivy et al investigated the impact of glucose consumption after a glycogen-depleting workout. Results showed that glucose given immediately following exercise increased muscle glycogen stores more quickly than even two hours later.10 Interestingly, carbohydrate at 1.5 grams per kilogram body weight was equally as effective as 3 grams per kilogram in the moments following. A later investigation revealed that glycogen stores were enhanced when subjects were given a mixture of protein and carbohydrate postexercise.11

Despite this evidence, postworkout refueling is frequently overlooked. Kundrat agrees: “In my experience working with endurance athletes, the most underutilized nutrition boost is recovery fuel.” Kundrat has found that many athletes believe they shouldn’t eat right after workouts, or focus only on protein. In response, she encourages her athlete clients “to take in at least 50 grams of carbohydrate and 15 to 20 grams of protein within 15 to 30 minutes after a hard workout to help restore muscle glycogen stores and encourage recovery of muscle tissue.” Kundrat suggests recovery drinks, shakes, and meal replacements and adds, “It is especially critical for low-weight athletes who have such limited ability to store glycogen because of their smaller muscle mass.”

A Message to Take to the Track
Athletes need fuel to sustain their rigorous schedule and enhance their workouts. Attention to timing is essential—before, during, and after exercise. Whether you are working with sponsored athletes or marathon enthusiasts, helping them eat for endurance will improve their performance, enhance their workouts, and keep them healthy.

— Jenna A. Bell-Wilson, PhD, RD, LD, is an assistant professor of clinical allied medicine in medical dietetics at The Ohio State University, a nutrition writer, and an endurance runner.

— Pamela Nisevich is a student in the combined master’s/dietetic internship program in medical dietetics at The Ohio State University.

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References
1. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc. 2000;100(12):1543-1556.

2. Hargreaves M, Hawley JA, Jeukendrup A. Pre-exercise carbohydrate and fat ingestion: Effects on metabolism and performance. J Sports Sci. 2004;22(1):31-38.

3. Cramp T, Broad E, Martin D, et al. Effects of preexercise carbohydrate ingestion on mountain bike performance. Med Sci Sports Exerc. 2004;36(9):1602-1609.

4. Schabort EJ, Bosch AN, Weltan SM, et al. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Med Sci Sports Exerc. 1999;31(3):464-471.

5. Jeukendrup AE. Carbohydrate intake during exercise and performance. Nutrition. 2004;20(7-8):669-677.

6. Utter AC, Kang J, Nieman DC, et al. Carbohydrate supplementation and perceived exertion during prolonged running. Med Sci Sports Exerc. 2004;36(6):1036-1041.

7. Almond CSD, Shin AY, Fortescue EB, et al. Hyponatremia among runners in the Boston Marathon. N Engl J Med. 2005;352(15):1550-1556.

8. Shirreffs SM. The importance of good hydration for work and exercise performance. Nutr Rev. 2005;63(6 Pt 2):S14-S21.

9. Levenhagen DK, Gresham JD, Carlson MG, et al. Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. Am J Physiol Endocrinol Metab. 2001;280(6):E982-E993.

10. Ivy JL, Lee MC, Brozinick JT Jr, et al. Muscle glycogen storage after different amounts of carbohydrate ingestion. J Appl Physiol. 1988;65(5):2018-2023.

11. Ivy JL, Goforth HW Jr, Damon BM, et al. Early postexercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement. J Appl Physiol. 2002;93(4):1337-1344.

Menu Choices Before, During, and After Exercise
Athletes are looking for recommendations that include actual food items. Here are some ideas to share, and remember the most important advice: Try everything during training. Do not add new foods on the day of an event.

Before Exercise:
• Multigrain cereal (40 grams carbohydrate)

• 2 pieces of whole grain toast (50 grams carbohydrate)

• 1 medium apple (20 grams carbohydrate)

• 15 animal crackers (50 grams carbohydrate)

• 2 packets of instant oatmeal (60 grams carbohydrate)

• 1 English muffin (26 grams carbohydrate)

During Exercise:
• 16 ounces of Gatorade (28 grams carbohydrate)

• 2 energy gel packets (~56 grams carbohydrate)

• 1/2 cup dried apricots (40 grams carbohydrate)

• 1/2 cup raisins (57 grams carbohydrate)

• 1 energy bar (~45 grams carbohydrate)

• 1 ounce of hard, salted pretzels (22 grams carbohydrate)

• 2 T honey (34 grams carbohydrate)

After Exercise:
• 1 cup 2% chocolate milk (26 grams carbohydrate)

• 2 T natural peanut butter on whole wheat bread (53 grams carbohydrate)

• 1 energy bar (~45 grams carbohydrate)

• 1 cup fresh orange juice (25 grams carbohydrate)

• Low-fat raisin granola bar (50 grams carbohydrate)

• 3 ounces of turkey breast and whole wheat pita pocket, 6.5 inches (70 grams carbohydrate)

• 1 cup seedless grapes (28 grams carbohydrate)