Sport relieves stress, builds self-confidence, encourages interaction with peers, and lets you compete against yourself. All this is also possible for children and adolescents with diabetes. The only thing that children with diabetes and their parents must know is the effect physical exertion has on blood sugar levels.

Those who exercise, or are physically active, use more energy. The body takes this energy from the readily available blood sugar. To enable this process, the hormones insulin and glucagon work together in an opposing fashion. During prolonged exercise, the insulin level drops. This triggers glucagon to enable the sugar storages (glycogen) in the liver and the muscles to release additional sugar as needed. The movement of the muscles enhances the effect of the insulin, which enables the muscle cells to take up the sugar more easily. After sport, the sugar storages are replenished. In this way, the blood glucose levels can always remain within normal range.

What happens in diabetes?
Exogenous insulin has a fixed function and duration, depending on the type and amount used. Consequently, the insulin level cannot drop during exercise. In turn, the glucagon cannot enable sufficient sugar storages in the liver and muscles to be released. And, as the muscle exertion enhances the effect of insulin so that the muscle cells can take up the sugar more easily, a subsequent hypoglycaemia is to be expected. 

Necessary steps
Basically, the blood sugar should always be monitored prior to exercise. Dextrose should always be on hand. It is also advisable to keep carbohydrate drinks and energy bars available such as yoghurt drinks, and muesli or chocolate bars. To avoid hypoglycaemia, the dosage of insulin must be reduced, and/or consume extra carbohydrates consumed before, during, and after sport.

Sport in schools and clubs
Sport in school or in clubs, as well as physical exertion such as newspaper delivery, lawn mowing, bike riding, or disco dancing can easily be planned for in advance. One simply has to take less insulin, and keep carbohydrates handy. Exactly how much to reduce the insulin dosage, or how much additional carbohydrate to consume, depends on the level of fitness, the time and duration of the exertion, as well as the type of insulin therapy.

It is very important to inform the coaches or trainers of the diabetes.

Reduce the insulin dosage? How?
Insulin should always be reduced by 30–50% at the peak of activity, depending on the level of fitness. However, long-acting insulin analogues, such as Lantus®, should not be reduced for short bursts of activity, as the reduced amount would not be adequate for the usual duration of effect. With pump therapy, the basal rate should be reduced at the time of activity and a few hours afterwards.

How much carbohydrate?
People acquire a feeling for their own blood sugar levels before and after sport through regular monitoring. It is recommended to eat one additional serving of carbohydrate (bread, yoghurt, muesli or chocolate bar) at pre-sport values under 160 mg/dl (8.9 mmol/l), and at pre-sport values under 100 mg/dl (5.6 mmol/l), to eat even more carbohydrate (dextrose, banana, fruit juice and bread, yoghurt, muesli or chocolate bar). With gymnastics or scored games such as tennis/squash/table tennis, the insulin dosage must be reduced before and afterwards. As already mentioned, the insulin should be reduced according to the peak level of activity. In general, one needs to take in extra carbohydrate. It is essential to reduce insulin after intensive sport. Remember that exertion enhances the effect of insulin! 

Planned or spontaneous?
With spontaneous physical exertion, the extra energy used must be replenished by consuming extra carbohydrate. For a whole-day’s bicycle tour, hiking or skiing, the usual insulin dosage should be reduced by up to 50% depending on individual level of fitness. Those on pumps should reduce the basal rate for that particular day. The fast-acting insulin (bolus) should also be reduced.

High blood sugar and sport
If the pre-sport measurements consistently show values of over 250 mg/dl (13.5 mmol/l), the blood or urine should be tested for ketones. High blood sugar values and ketones are an indication for severe insulin deficiency. In this case, sport should not be undertaken at all. If so, severe metabolic disorders can occur (ketoacidosis). Those on pumps must correct the high blood sugar values of over 200 mg/dl (11 mmol/l) before undertaking any kind of sport. Whichever way, with values over 200 mg/dl (11 mmol/l), a test for ketones should be carried out.
 
Seven-point plan for maximum sport enjoyment

• Measure blood sugar before sport!
• Keep carbohydrates handy (eg, chocolate bars).
• Avoid hypoglycaemia by reducing insulin and/or eating extra carbohydrates.
• Reduce insulin after sport.
• Consistent values over 250 mg/dl (13.5 mmol/l) should be tested for ketones in blood or urine.
• Definitely reduce insulin after intensive sport-insulin effect is enhanced.
  Inform trainers and coaches of your diabetes.

Margret Petersen
Diabetes consultant for the German Diabetes Society (DDG) / Dietary assistant
Universitätsklinikum Schleswig-Holstein
Tel.: 0451/500-2167
E-Mail: petersen(at)paedia.ukl.mu-luebeck(dot)de