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From Cedar Rapids, Iowa, USA:

My cousin, an R.N., says she has heard that diabetic marathon runners often "charge" themselves with extra carbohydrates for a few days prior to running. If so, what does it entail, and would it help her two daughters (ages 13 & 16) who are Type 1 (both diagnosed at age 3)?

They are avid volleyball players for their school and metro teams. When they play in very intensive 2-day tournaments, they cut back their Humalog 2-units starting the morning just before the tourney (assuming a blood glucose of 150 or less) and stay at that dose until they finish their last game, the next afternoon or evening. They leave their Ultralente at night the same. Also, they eat/drink fruit and juices, pudding, etc. in addition to their regular meals, yet they still "run out of steam" during the second day's games. Any thoughts would be appreciated.


Research has shown that a particular combination of diet and exercise results in a significant "packing" of muscle glycogen. The term carbohydrate loading or supercompensation is used for this procedure among endurance athletes. The classic procedure for achieving the supercompensation effect is to reduce the muscle's glycogen content with prolonged steady rate exercise 6 days before competition. Because supercompensation occurs only in the specific muscles exercised, the athlete should be sure to engage the muscles involved in his/her sport. (For a marathon runner, a 15 to 20 mile run is usually necessary, whereas for bicycling, moderately intense submaximal exercise for 90 minutes is required.) Then the athlete maintains a low-carbohydrate diet for several days to further deplete glycogen stores. During this time moderate training is continued. Then, at least two days before the competition, the athlete switches to a high-carbohydrate diet and maintains it up to and including his/her pre-game meal. The 2 to 3 day requirement for a high carbohydrate diet is important because it generally takes this long for full restoration of muscle glycogen following severe depletion.

Athletes with diabetes should not practice carbohydrate loading, especially if it requires a period of time where carbohydrate restriction in included. Adjustment of insulin dosages to this practice is just too difficult. However, on pre-competition day, I would suggest that the girls eat more foods that are high in carbohydrate and decrease their training to increase glycogen stores. Because regular exercise requires frequent replenishing of stored carbohydrate, more carbohydrate may be needed in their diet. Remember that the girls' insulin dosages may need to be increased slightly during this period.

Depleted glycogen stores can cause fatigue and poor performance. This may be why the girls are running out of steam on the second day of their tournament.

Here are some suggestions for food intake that might be helpful to your cousin and her girls:

  1. The night before their competition, the girls should try to eat a high carbohydrate meal to increase glycogen stores. Examples of carbohydrate meal to increase glycogen stores. Examples of foods that are high in carbohydrates are spaghetti, rice, potatoes, squash, noodles, bread, muffins, yogurt, rolls, etc. Avoid foods that contain large amounts of fat in addition to carbohydrate, such as pizza and ice cream.

  2. On the day of competition, the girls should try to eat a light breakfast. Toast, juice or fruit, and cereal with skim milk are good choices. For lunch, a turkey sandwich with skim milk and fruit.

  3. A light pre-game meal should be eaten 1 to 2 hours before the event. (Carbohydrate and protein but a minimal amount of fat.) If too much protein is ingested and too little carbohydrate, the girls will deprive their muscles the energy they need to perform well.

Another reason the girls may run out of steam is that they may not be adding enough carbohydrate during their activity period. Fruit juice can be a good source of carbohydrate and fluid but should be diluted with water (1 part water [1 cup] to 1 part juice [1 cup juice]). They may want to consume 10 to 15 grams of carbohydrate every hour during a long event.

A reference that may be of some additional help is Nutrition and Sports Performance: A Guide for Physically-Active Young People, a pamphlet put out by the American College of Sports Medicine, P.O. Box 1440, Indianapolis, IN 46206-1440.


Original posting 18 Apr 97


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Last Updated: Tuesday April 06, 2010 15:08:54
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