# Exercise as it relates to Disease/Preventing hypoglycemia in type 1 diabetics during and after exercise
## Definitions
#### Type 1 Diabetes

Type 1 diabetes is a chronic disease in which the beta cells of the pancreas are destroyed and cannot produce insulin, the hormone that is responsible for the uptake of glucose from the blood. Type 1 diabetes accounts for around 10 to 15% of all diabetics with over 16 million people worldwide diagnosed with the disease. Regular insulin injections are required to increase the amount of glucose extracted from the blood and utilized within the body for energy.

#### Hypoglycemia

Hypoglycemia is a state of low blood glucose in which circulating blood glucose levels drop below 3.5 mmol/l. Hypoglycemia may occur as a result of excessive insulin dosages, low glucose intake eg: missing a meal or not eating enough carbohydrates and/or participating in prolonged or unplanned exercise. Severe hypoglycemia can lead to seizures,coma and death.
Symptoms of hypoglycemia include:
* Shaking, Trembling & Quivering
* Abnormal Heart Beat
* Anxiety & Arousal
* Paleness & Sweating
* Increased Appetite
* Tingling & Numbness
* Increased Body Temperature
* Weakness & Fatigue
* Confusion
* Behavioural changes
* Involuntary Crying

## Exercise Complications

Participation in exercise generally increases the risk for type 1 diabetics to develop hypoglycemia during exercise and up to 24 hours after completion. The body becomes more sensitive towards insulin causing insulin to be utilized at a greater rate, this can lead to an abrupt drop in blood glucose levels. In healthy individuals the body has mechanisms that counteract this problem these are known as counterregulatory responses. Healthy counterregulatory responses to lowering blood glucose levels show a decrease in insulin production and an increase the production and release of glucose. In type 1 diabetics these counterregulatory responses are diminished as the body is not able to decrease the amount of synthetic insulin administered via injections, glucose raising responses are also weakened in type 1 diabetics. In saying this individuals should not be limited in regards to sport participation and can partake in exercise with simple manipulations of insulin injections, carbohydrate intake and exercise intensity while regularly monitoring blood glucose levels to help maintain adequate blood glucose control.

## Exercise Recommendations
#### Insulin Administration

As mentioned above type 1 diabetics have impaired counterregulatory responses to exercise and therefore are unable to lower the amount of synthetic insulin circulating within the body, therefore it is important to reduce the amount of insulin injected to offset this problem. The total amount of insulin reduced relies on many factors these include: duration and intensity of exercise, blood glucose and insulin levels and environmental factors. General guidelines for insulin administration prior to exercise involve:
* Injecting insulin into the subcutaneous fat layer underneath the skin in either the abdomen or non exercising muscle.
* Lowering the pre-meal insulin dosages by 25-75%.
* Lowering the pre-meal insulin dosages by 70-80% if exercise is long in duration >90minutes.
* Lowering the rapid pre-meal insulin dosage by 30-50% if exercise is up to 4hours in duration.
* Lowering the pre meal insulin dosages by 70-90% in team sports, this may not be necessary if duration is less than 60minutes.
As mentioned these are only guidelines, the exact insulin adjustments should be made on an individual basis via the use of a trial and error approach.

#### Carbohydrate Intake

Similar to insulin administration, carbohydrate intake should be altered prior to exercise. Insulin becomes more effective as a result of exercise and as previously stated the body is unable to alter the synthetic amount of insulin administered within the body therefore as glucose levels decline insulin levels will not decrease accordingly resulting in an increase in glucose utilization and potential hypoglycemia. This problem can be counteracted by:
* Consuming low glycemic index (GI) foods
* Consuming a carbohydrate rich snack 3 hours prior to exercise.
* Consuming extra carbohydrates during prolonged exercise
* Consuming post-exercise carbohydrates within 30 minutes of exercise completion.
* Always carrying a carbohydrate rich snack or drink while exercising.
Carbohydrate intake recommendations:
| Exercise stage | Carbohydrate (CHO) intake | Example's |
| Prior | 15g CHO per 30minutes exercise. | 1 bannana 1/2 cup cooked pasta 1 glass fruit juice |
| During | 60-80g CHO per 1hour exercise or 1g per kg of body weight per 1hour exercise | 1 musli/sports bar 1-2 sports gels 500ml Gatorade/Powerade |
| After | 1.5g of CHO per kg of body weight post exercise repeat after 2 hours | Multigrain sandwiches Pasta/Rice Fresh fruit DO NOT drink alcohol |

#### Exercise Prescription

Exercise can have a major role on blood glucose levels as the body relies mainly on carbohydrates during high intensity exercise for a fuel source this can cause rapid depletion of blood glucose levels if insulin injection and carbohydrate intake are not modified. General exercise prescriptions to avoid abrupt decreases in blood glucose levels include:
* Avoid exercise if an individual has had low blood glucose <5 mmol/l or has recently had a hypoglycemic attack in the prior 24 hours.
* Avoid exercise if an individual has had an intense training session or competition in the prior 24 hours.
* Avoid spontaneous and unplanned exercise, especially if insulin has recently been administered.
* Perform exercise in the morning before insulin administration if able to.
Exercise effects on blood glucose regulation:
| Intensity | Duration | % Vo2max | Effects on blood glucose | Example |
| Medium | 30min | 40-60% | Decrease | Running, Cycling |
| High | <15min | >80% | Increase | Sprinting |
| Team Sports | 30min | 40-60% w/ Short sprint's | Slight Decrease | Rugby, Soccer |

## Blood Glucose Monitoring

Self monitoring of blood glucose before, during and after exercise is recommended to distinguish when changes in insulin or carbohydrate intake are needed, monitoring of blood glucose can also provide an insight into the response of blood glucose towards various types of physical activity.

## Further Information

* American Diabetes Association
* Diabetes Australia
* National Diabetes Information Clearinghouse (NDIC)

## References

* ↑ Powers, S.K., Howley, E.T. (2009). Exercise Physiology: Theory and applications to fitness and performance 7th edition. Mcgraw-Hill Companies, Inc. New York
* ↑ Guelfi, K.J., Jones, T.W. & Fournier, P.A. 2007, "New insights into managing the risk of hypoglycaemia associated with intermittent high-intensity exercise in individuals with type 1 diabetes mellitus: implications for existing guidelines", Sports Medicine, vol. 37, no. 11, pp. 937-946
* ↑ Cryer, P.E., Davis, S.N. & Shamoon, H. 2003, "Hypoglycemia in diabetes", Diabetes care, vol. 26, no. 6, pp. 1902
* ↑ Guelfi, K.J., Jones, T.W. & Fournier, P.A. 2007, "New insights into managing the risk of hypoglycaemia associated with intermittent high-intensity exercise in individuals with type 1 diabetes mellitus: implications for existing guidelines", Sports Medicine, vol. 37, no. 11, pp. 937-946
* ↑ Cryer, P.E., Davis, S.N. & Shamoon, H. 2003, "Hypoglycemia in diabetes", Diabetes care, vol. 26, no. 6, pp. 1902.
* ↑ Ertl, A. & Davis, S. 2004, "Evidence for a vicious cycle of exercise and hypoglycemia in type 1 diabetes mellitus", Diabetes/metabolism research and reviews, vol. 20, no. 2, pp. 124-130
* ↑ Briscoe, V.J.B.V.J., Tate, D.B.T.D.B. & Davis, S.N.D.S.N. 2007, "Type 1 diabetes: exercise and hypoglycemia", Applied Physiology, Nutrition, and Metabolism, vol. 32, no. 3, pp. 576-582
* ↑ Powers, S.K., Howley, E.T. (2009). Exercise Physiology: Theory and applications to fitness and performance 7th edition. Mcgraw-Hill Companies, Inc. New York
* ↑ Toni, S., Reali, M.F., Barni, F., Lenzi, L. & Festini, F. 2006, "Managing insulin therapy during exercise in type 1 diabetes mellitus", Acta Biomed, vol. 77, no. suppl 1, pp. 34-40
* ↑ Rabasa-Lhoret, R., Bourque, J., Ducros, F. & Chiasson, J.L. 2001, "Guidelines for premeal insulin dose reduction for postprandial exercise of different intensities and durations in type 1 diabetic subjects treated intensively with a basal-bolus insulin regimen (ultralente-lispro)", Diabetes care, vol. 24, no. 4, pp. 625.
* ↑ Toni, S., Reali, M.F., Barni, F., Lenzi, L. & Festini, F. 2006, "Managing insulin therapy during exercise in type 1 diabetes mellitus", Acta Biomed, vol. 77, no. suppl 1, pp. 34-40.
* ↑ Coker, R.H., Koyama, Y., Denny, J.C., Camacho, R.C., Lacy, D.B. & Wasserman, D.H. 2002, "Prevention of overt hypoglycemia during exercise", Diabetes, vol. 51, no. 5, pp. 1310.
* ↑ Powers, S.K., Howley, E.T. (2009). Exercise Physiology: Theory and applications to fitness and performance 7th edition. Mcgraw-Hill Companies, Inc. New York
* ↑ Galassetti, P., Mann, S., Tate, D., Neill, R.A., Wasserman, D.H. & Davis, S.N. 2001, "Effect of morning exercise on counterregulatory responses to subsequent, afternoon exercise", Journal of applied physiology, vol. 91, no. 1, pp. 91.
* ↑ Guelfi, K.J., Jones, T.W. & Fournier, P.A. 2007, "New insights into managing the risk of hypoglycaemia associated with intermittent high-intensity exercise in individuals with type 1 diabetes mellitus: implications for existing guidelines", Sports Medicine, vol. 37, no. 11, pp. 937-946
* ↑ Guelfi, K.J., Jones, T.W. & Fournier, P.A. 2007, "New insights into managing the risk of hypoglycaemia associated with intermittent high-intensity exercise in individuals with type 1 diabetes mellitus: implications for existing guidelines", Sports Medicine, vol. 37, no. 11, pp. 937-946.
* ↑ Ertl, A. & Davis, S. 2004, "Evidence for a vicious cycle of exercise and hypoglycemia in type 1 diabetes mellitus", Diabetes/metabolism research and reviews, vol. 20, no. 2, pp. 124-130.
* ↑ Powers, S.K., Howley, E.T. (2009). Exercise Physiology: Theory and applications to fitness and performance 7th edition. Mcgraw-Hill Companies, Inc. New York.