# Exercise as it relates to Disease/Aerobic or anaerobic: effect of exercise type on blood glucose in type 1 diabetics

Type 1 Diabetes Mellitus (T1DM) is an autoimmune disease which affects the insulin producing beta cells within the pancreas. Insulin is used to lower blood glucose levels by allowing the cells to absorb glucose. Treatment for people with T1DM involves regular insulin injections and constant blood glucose monitoring.

## Complications

| Acute | Effects |
| Hypoglycaemia (blood glucose below 4mM) | Weakness, shakiness, sweating, blurred vision, headaches, amnesia, seizures and coma. |
| Hyperglycaemia (blood glucose above 7mM) | Dehydration, frequent urination, excessive thirst and fatigue. |
| Chronic | Effects |
| Heart and blood vessels | Atherosclerosis, coronary and peripheral artery disease, hypertension, high cholesterol, cardiovascular disease. |
| Nerves | Neuropathies (both peripheral and autonomic) therefore increased risk of infection, burns and falls. |
| Eyes | Retinopathy and blindness. |
| Kidneys | Nephropathy. |

## Exercise and Type 1 Diabetes

Exercise is recommended for people with T1DM because it reduces the risk of diabetic complications and mortality, improves insulin sensitivity and reduces required daily insulin needs. Some physiological benefits associated with exercise also include improved physical work capacity, body composition, blood pressure and blood lipid profile.
Exercise for Type 1 Diabetics is generally associated with an increased risk of hypoglycaemia during and up to 31 hours of recovery, however, different types of exercise have shown to produce different effects on blood glucose levels.

## Aerobic Exercise

Generally prolonged, low to moderate intensity exercise where energy demands can be sustained by oxygen for example long distance running, swimming and cycling. For people with T1DM aerobic exercise usually results in a reduction in blood glucose levels due to:
* A greater reliance on carbohydrates as a fuel source.
* Increased insulin sensitivity within the muscles and stable plasma insulin levels which results in increased absorption.

## Anaerobic Exercise

Short duration, high intensity exercise which requires energy using ATP PC and glycolysis for example field events, sprinting, jumping and weight lifting. Anaerobic exercise generally results in sustained or increased blood glucose levels for approximately 1 hour post exercise. This occurs because:
* Catacholamine and cortisol levels increase therefore inhibiting insulin mediated glucose uptake and increase gluconeogenesis within the liver.
* Growth Hormone increases and aids in inhibiting insulin mediated glucose uptake.
* Increased lactate levels may be associated with inhibiting glucose uptake to the skeletal muscles.

## Recommendations

* Both aerobic and anaerobic exercise should be undertaken in order to achieve greater physiological benefits and enhance blood glucose control.
   * 150 minutes per week of moderate (40-60% heart rate max) or
   * 90 minutes per week of vigorous (above 60% heart rate max)
* Prior to the onset of exercise it is important to check blood glucose levels are at an appropriate level to help reduce the risk of hypo or hyper glycaemia.
* Reducing insulin doses may be necessary before and after exercise.
* In order to gain the physiological benefits of exercise it is recommended to complete 60 minutes of moderate intensity physical activity on most days of the week.
* After aerobic exercise it is recommended to complete a short bout of high intensity exercise to counteract a potential drop in blood glucose levels (A maximal 10 second sprint is sufficient).

## Further reading

* Diabetes Australia
* AIS Diabetes and Sports Nutrition

## References

* 1 2 K.G.M.M. Alberti, , P.Z. Zimmet, 1998. Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications. Diabetic Medicine, 15, 7, 539-553.
* ↑ Riddell. M, Iscoe. K 2006. Physical activity, sport and pediatric diabetes, Pediatric Diabetes, 7, 60-70.
* ↑ Guelfl. K, Jones. T, Fournier. P, 2005. The Decline in Blood Glucose Levels is Less With Intermittent High-Intensity Compared with Moderate Intensity Exercise in Individuals with Type 1 Diabetes, Diabetes Care, 28, 6, 1289-1294.
* ↑ Yardley. J, Kenny. G, Riddell. M, 2012. Effects of Performing Resistance Exercise Before Versus After Aerobic Exercise on Glycemia in Type 1 Diabetics, Diabetes Care, 35,669-675.
* 1 2 Bussau. V, Jones. T, Ferreira. L, Fournier. P, 2006. The 10-s Maximal Sprint, Diabetes Care, 29, 3, 601-606.
* ↑ Guelfi. K, Ratnam. N, Smythe. G 2007. Effect of intermittent high-intensity compared with continuous moderate exercise on glucose production and utilization in individuals with type 1 diabetes, Endocrinology and Metabolism, 292, 865-870.
* ↑ Allbright, A 2009. Diabetes, Clinical Exercise Physiology, 3, 6, 91-111.
* ↑ Australian Government Department of Health and Ageing, 2005. An Active Way to Better Health: National Physical Activity Guidelines for Adults, Department of Health and Aged Care, Canberra.