Factors that determine carbohydrate needs during exercise in diabetic athletes
Carbohydrate recommendations depend on timing of ingestion in relation to when exercise is performed. This will have an impact on the glycaemic index of the carbohydrate required. Use low glycemic index carbohydrates in the hours prior to exercise, and high glycemic index just before, during and immediately after exercise. Blood glucose measurements should be used to monitor the rate at which the body needs glucose. Additional factors that determine carbohydrate needs include:
- Type of exercise: Aerobic exercise such as running, swimming or cycling, produce greater glucose consumption and, therefore, have a stronger hypoglycaemic effect than anaerobic exercise such as sprinting and weights.
- Duration: The most significant changes in blood glucose occur after ~60 minutes of moderate or high-intensity exercise.
- Intensity: Glucose is the preferred muscle fuel for exercise performed at a moderate or high intensity. Therefore, low-intensity exercise such as walking may have a minimal effect on blood sugar, whereas intense exercise such as running could cause a stronger and faster blood glucose lowering effect.
- Frequency: Hypoglycaemic effects, especially after exercise, increase after several consecutive days of physical exercise.
- Schedule: Timing of insulin administration influences blood insulin levels throughout the day, which brings about a greater tendency to develop hypoglycemia during physical activity. This effect is more likely when exercise is performed within 2-3 hours after meals, when rapid-acting insulin acts the strongest.