Friday, May 11, 2007

Sports Nutrition Primer

Sports Nutrition Primer—
By Debra Wein.
From NSCA’s Performance Training Journal, NSCA
Depending on the duration, intensity, and type of exercise you are performing, there are three stages where nutrition plays a role in performance —before, during, and after activity. One of the primary goals of sport nutrition is to optimize the availability of muscle glycogen, thereby insuring optimal performance.

Pre-Exercise Nutrition
Properly nourishing yourself before exercise should:
-Prevent low blood sugar during exercise.
-Provide fuel by topping off your muscle glycogen stores.
-Settle your stomach, absorb gastric juices, and prevent hunger.
-Instill confidence in your abilities.

Remember, fasting is detrimental to performance, and is strongly discouraged before exercise or performance. The pre-exercise meal should consist primarily of high carbohydrate, low fat foods for easy and fast digestion. Since everyone’s preferences for, and responses to, different foods are unique, it is recommended that you learn through trial and error what does and does not work for you. For example, some people respond negatively to sugar intake within an hour before exercise. The temporary “boost” that some people experience after eating foods with a high sugar (sucrose) concentration such as candy, syrups, or soft drinks actually causes an increase in insulin production which will be followed by a rapid lowering of blood sugar, and can lead to decreased performance. In addition, fructose (the sugar present in fruit juices) ingested before exercise may also lower your blood sugar and cause gastrointestinal distress in some people, but not others.

How much time should you allow before exercise after eating?
-Allow adequate time for digestion and normalization of blood glucose:
-4 hours for a large meal.
-2 – 3 hours for a smaller meal.
-1 hour for a blended meal, a high carbohydrate beverage (10 – 30%), or a small snack.

During Exercise
When an individual has been consuming a diet sufficient in carbohydrates, 60% or greater, there is enough energy present in the muscles to fuel workouts and other activities completed within 60 – 90 minutes. On the other hand, during prolonged, strenuous exercise lasting over 90 minutes, carbohydrate ingestion at
regular intervals during the exercise is beneficial2, 3. For example, consuming 8 ounces (1 cup) of a sports drink containing a 6 – 10 % carbohydrate concentration every 15 – 20 minutes can delay the onset of fatigue. This is equivalent to a rate of 0.8 – 1.0 grams of carbohydrate per minute or approximately 24 – 30 grams every half hour.

Post-Exercise Nutrition
When and what you eat after a work-out can have a serious effect on your recovery. Adequate recovery means that your muscles are rested, re-fueled, and ready to perform again, which is extremely important for people who exercise every day. Inadequate recovery can lead to chronic fatigue and a gradual decline in your performance. Be selective in what you eat after exercise; wise choices will help you recover quickly and enable your muscles to work better the next time around. For the fitness enthusiast whose workouts generally last less than 90 minutes, your main concern is to re-fuel with a well-balanced, high carbohydrate diet. However, if your workouts typically last longer than 90 minutes and are “exhaustive,” the timing of your meals is additionally important. Your body needs about 20 hours to replenish its fuel stores. Furthermore, this will only occur if adequate carbohydrate (approx. 500 – 600 grams depending on your body size) is consumed during this time2, 3. The first 2 – 3 hours after exercise are critical for you—don’t wait to eat.

For optimal glycogen re-synthesis, follow these target intakes during the 20 hours following a workout:
-Immediately after exercise (15 – 30 minutes): 75 – 100 grams carbohydrate.
-Within the next 2 – 3 hours after exercise: 100 grams carbohydrate.
-Every 4 hours thereafter: 100 grams carbohydrate.

For example, since 1 gram carbohydrate
= 4 calories, 75 – 100 grams = 300 – 400 calories. In practical terms, you could take in 75 – 100 grams of carbohydrate by eating:
-A banana and a bagel.
-1⁄2 cup raisins and a slice of bread.
-2 cups of orange juice and a cup of yogurt.

Current research also suggests that protein, when consumed along with the post carbohydrate fuel, can increase the rate of glycogen resynthesis and improve recovery1. A high carbohydrate beverage (10 – 30% carbohydrate concentration) can also be used as an immediate source of carbohydrate replenishment. These beverages can be especially useful after a workout in the heat when you may be more inclined to drink than to eat. However, high carbohydrate beverages are not complete foods; they do not contain all the nutrients your body needs for good health and top performance. If you use these beverages in your training regimen, make sure you follow soon after with a well-balanced, high carbohydrate meal, and plenty of fluids.

1. Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M, Keizer HA, van Loon LJ. (2004). The combined ingestion of protein and free leucine with carbohydrate increases post exercise muscle protein synthesis in vivo in male subjects, American Journal of Physiololgy – Endocrinology and Metabolism, Nov 23.
2. Position of the ADA, Dietitians of Canada, and the American College of Sports Medicine. (2000). Nutritionand athletic performance. Journal of the American Dietetics Association, 100:1543 – 1556.
3. Rosenbloom C. (2000). Sports nutrition, A guide for the professional working with active people, Third Edition. Chicago; The American Dietetic Association.

About the Author
Debra Wein, MS, RD, LDN, NSCACPT is on the faculty at The University of Massachusetts Boston and Simmons College. She chairs the Women’s Subcommittee of the Massachusetts’ Governor’s Committee on Physical Fitness and Sports and is the President of The Sensible Nutrition Connection, Inc. (

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