The Importance of Exercise for people with Diabetes Mellitus

The benefits of regular exercise for anyone, regardless of age, gender or ability, cannot be overstated. Exercise helps to improve mood and sleep, improve muscle strength and bone mass, lower blood glucose levels (BGLs), lower cholesterol, triglycerides and blood pressure, improve heart and blood vessel health, maintain or achieve your healthiest body weight, reduce stress and anxiety, and improve mental health.

 

For those at risk of or diagnosed with diabetes mellitus exercise provides specific advantages including improve overall and disease-specific quality of life, may enhance or improve insulin sensitivity, contribute to an increased metabolism which plays a role in the regulation of body weight, and increases self-efficacy for maintaining normal blood glucose levels by learning about the short- and long-term benefits of optimal control and how to manage blood glucose before, during, and after exercise.

 

Research into the effect of exercise for those with diabetes mellitus highlight that;

-          Exercise can lower HbA1c values by 0.7% in people regardless of which medication or variety of diet they were engaging with

-          All forms of exercise - aerobic, resistance, or doing both – was equally effective at lowering HbA1c values in people with diabetes

- whilst both resistance training and aerobic training has been proven to help lower insulin resistance in previously sedentary older adults with abdominal obesity at risk for diabetes, combination training has proven more beneficial than doing either one alone.

-          Those with diabetes who walk at least 2 hours a week are less likely to die of heart disease than those who are sedentary, and those who exercise 2 - 4 hours a week reduce their risk even more.

-          Women with diabetes who participated in at least 4 hours of moderate – vigorous exercise a week had a 40% lower risk of developing heart disease than those who didn't exercise

-          Research has shown that the benefits of exercise persist even when accounting for differences in BMI, smoking status, and presence of other heart disease risk factors

 

So what is Diabetes Mellitus?

Diabetes mellitus, or diabetes, is a condition where there is too much glucose in the blood. The body is unable to make insulin, enough insulin or is not effectively using the insulin it does make. Over time high glucose levels (hyperglycaemias) can damage blood vessels and nerves, resulting in long term health complications including heart, kidney, eye and foot damage. Diabetes is not a single condition. In fact there are three main types of diabetes: Type 1, Type 2 and Gestational diabetes. Additionally, Pre-diabetes may be diagnosed before it progresses to Type 2 diabetes. Diabetes does not discriminate, anyone can develop diabetes.

 

Type 1 diabetes is an autoimmune condition (10% of all diabetes cases) where the body’s own immune system is activated to destroy the beta cells in the pancreas resulting in the pancreas being unable to produce insulin. The exact causes of this autoimmune reaction are currently unknown however it has been linked to environmental factors. Type 1 diabetes is not linked to modifiable lifestyle factors and as such there is no cure and requires lifelong management. Type 1 Diabetes is one of the most common chronic childhood conditions and onset is usually abrupt and the symptoms obvious, whereas in adults the onset is slower. Symptoms can include excessive thirst and urination, unexplained weight loss, weakness and fatigue and blurred vision. Type 1 Diabetes is managed with insulin injections several times a day or the use of an insulin pump, and if untreated can results in diabetic ketoacidosis (DKA), a medical emergency.

 

Type 2 diabetes (85–90% of all cases) is a condition in which the body becomes resistant to the normal effects of insulin and gradually loses the capacity to produce enough insulin in the pancreas. The condition has strong genetic and family-related (non-modifiable) risk factors and is also often associated with modifiable lifestyle risk factors. Type 2 diabetes usually develops in adults over the age of 45 years but is increasingly occurring in younger age groups including children and adolescents. Symptoms can go unnoticed or be seen as signs of aging and include feeling tired and lethargic, cuts that heal slowly or recurring skin infections, unexplained weight loss or weight gain. Type 2 diabetes is managed with a combination of regular physical activity, healthy eating, and weight reduction. However as type 2 diabetes can be progressive, many people will need oral medications and/or insulin injections in addition to lifestyle changes over time.

 

Research shows that it is possible for some people with type 2 diabetes to enter remission, which is defined as an HbA1c of under 6.5% (48mmol/mol) for at least three months without the need for glucose-lowering medications. It is important to note that remission DOES NOT mean type 2 diabetes is cured or reversed – it simply means that blood glucose levels are now being maintained below type 2 diabetes levels. Continued regular diabetes monitoring and annual health checks should be prioritised as some of the macrovascular and microvascular damage which cause long term complications has already begun.

 

Pre-diabetes describes a condition in which blood glucose levels are higher than normal, although not high enough to be diagnosed with type 2 diabetes. Pre-diabetes has no signs or symptoms. Currently 2 million Australians have pre-diabetes and are at high-risk of developing type 2 diabetes. Without sustained lifestyle changes which includes healthy eating, increased regular physical activity and maintenance of a healthy weight approximately 5-10% of people with pre-diabetes will go on to develop type 2 diabetes each year.

 

Gestational diabetes mellitus (GDM) is a type of diabetes that occurs during pregnancy and is the fastest growing type of diabetes in Australia, occurring in 5-10% of pregnancies. Women with gestational diabetes can still have a healthy baby but it is important that gestational diabetes is managed to reduce the risk of developing complications during pregnancy. Gestational diabetes is diagnosed when higher than normal blood glucose levels first appear during pregnancy, most commonly during testing at 24-28 weeks of pregnancy (except those women who already have diabetes). Women who have risk factors for gestational diabetes should be tested earlier in their pregnancy. Gestational diabetes can often be managed with healthy eating and regular physical activity. However, some women may need medication (metformin) and/or insulin injections to help manage gestational diabetes.

 

So how does Diabetes affect the Body?

 

Glucose is a form of sugar and is the main source of energy for the cells that make up our muscles, other tissues, and the brain. For our bodies to work properly we need to be able to maintain a balance of converting carbohydrates from our food into glucose (or if we don’t have access to enough carbohydrates our body will convert fat and protein into glucose) and our pancreas producing insulin which transports the glucose from our blood stream into our cells to be used as fuel. In people with diabetes, depending on the type of diabetes, insulin is either no longer produced or not enough is produced or the body doesn’t use it as well as it used to. Therefore, when we ingest carbohydrates the imbalance of insulin results in glucose being unable to leave the blood stream and enter the cells resulting in high blood glucose levels. High levels of glucose in the blood can lead to long term and short term health complications.

 

 

Exercise with Diabetes Mellitus Guidelines

 

Aim to engage in aerobic exercise for at least 150 min a week of moderate intensity exercise (40% and 60% Heart Rate Reserve – think of a brisk walk), shared over a minimum of 3 days a week with no more than 2 consecutive days between exercise sessions due to the short duration of improvements in insulin function. Any types of exercise that use large muscle groups (i.e., swimming, cycling, walking, running, rowing) are recommended.

 

The recommended amount of aerobic exercise for the general population is 5 times a week of moderate intensity or 3 times a week of vigorous intensity.

 

Aim to engage in resistance exercise 2-3 times a week with a minimum of 48-72 hours between sessions that targeted any given muscle group. Training sessions should be moderate (50% of an individual’s one repetition maximum (1RM)) or vigorous (75% to 80% of the 1RM) consisting of 1-4 sets of 10-15 repetitions of 5-10 exercises, depending on the individual’s level of fitness, for optimal improvements in strength and insulin action. It is recommended that sessions be primarily based on resistance machines and free weights with the use of additional accessories including bands, cables, and body weight. Secondary functional movement exercises that allow the client to simulate activities of daily living should be a focus to improve disease-specific and overall quality of life.

 

Children should be encouraged to engage in at least 60 minutes a day of moderate to vigorous aerobic physical activity, and at least 3 times a week of muscle and bone strengthening activities.

 

Timing of Exercise and Blood Glucose Levels

In general, the best time to exercise is 1 - 3 hours after eating when your blood sugar level is likely to be higher. If you use insulin, it's important to test your blood sugar before exercising to ensure you are not hypoglycaemic or hyperglycaemic.  

 

Hypoglycaemia or a low BGL (4.0 mmol/L or less) can occur in people who inject insulin or take a type of glucose lowering medication. Exercise causes muscles to use more glucose which lowers your BGLs.

 

Reduce the risk of hypoglycaemia during and after exercise by:

  • checking your BGLs before exercise – make sure your BGL is at least 7.0 mmol/L before exercise

  • checking your BGL regularly during and after exercise, particularly after an intense workout or activity as if you're taking insulin your risk of developing hypoglycaemia is highest 6 to 12 hours after exercising.

  • increasing your carbohydrate intake as necessary according to intensity, duration and type of exercise

  • decreasing medication or insulin as necessary, after talking to your doctor.

 

Your risk of hypoglycaemia during exercise is increased with:

  • type 1 diabetes

  • treatment includes injection of insulin or take a sulphonylurea

  • recurring episodes of hypoglycaemia

  • inability to detect the early warning signs and symptoms of hypoglycaemia

  • an episode of hypoglycaemia before exercise (as both exercise and hypoglycaemia reduce your ability to detect further hypoglycaemia)

  • alcohol consumption before exercise (alcohol reduces your ability to detect hypoglycaemia).

 

Hyperglycaemia or a high BGL (over 11 mmol/L) can occur when there is an imbalance of glucose and insulin. Exercising when your blood glucose is higher than normal can lower your levels. However, if you are unwell and your BGLs are very high it is best to avoid exercising until your BGLs have returned to the normal range. People with diabetes who have BGLs above the normal range are more at risk of dehydration so it is important to stay hydrated when engaging with exercise.

 

Ketoacidosis, a build-up of ketones can occur when people with type 1 diabetes are unwell or have forgotten to take their insulin. If you receive a BGL reading above 15 mmol/L, positive for blood or urine ketones, you will need to inject extra insulin to assist in clearing them before engaging with exercise. People with type 2 diabetes are generally not at risk of developing dangerous levels of ketones (unless taking a SGLT-2 inhibitor) and therefore do not need to check for them.

 

Take Aways

-          Before you start exercising, make sure you see your GP and a diabetes health professional for an individual management plan.

-          See an Exercise Physiologist who can guide your exercise sessions and develop a personalised exercise plan for you.

-          Check your blood glucose levels (BGLs) before, during and after exercise to see how the exercise you are doing affects them.

-          If your BGLs are above the normal range before exercise refer to your diabetes management plan. If you are unwell and your BGLs are high, avoid exercising until your BGLs have returned to the normal range and you are feeling better.

-          If you have type 1 diabetes and you are unwell, avoid exercise until you feel better as you may be at risk of ketoacidosis.

-          Always carry portable hypoglycaemia treatment with you if you take insulin or sulphonylurea medication

Rachel Morgan-Varlow