Chapter 10: Physical Activity and Diabetes
Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada
Types of Exercise
- Aerobic exercise is physical activity, such as walking, bicycling or jogging, that involves continuous, rhythmic movements of large muscle groups lasting for at least 10 minutes at a time.
- Resistance exercise is physical activity involving brief repetitive exercises with weights, weight machines, resistance bands or one's own body weight (e.g. pushups) to increase muscle strength and/or endurance.
- Flexibility exercise is a form of activity, such as lower back or hamstring stretching, that enhances the ability of joints to move through their full range of motion.
Benefits of Physical Activity
Physical activity (exercise) can help people with diabetes achieve a variety of goals, including increased cardiorespiratory fitness, increased vigour, improved glycemic control, decreased insulin resistance, improved lipid profile, blood pressure reduction and maintenance of weight loss.
Benefits of Aerobic Exercise
- Moderate to high levels of aerobic physical activity and higher levels of cardiorespiratory fitness are associated with slowing the development of peripheral neuropathy and substantial reductions in morbidity and mortality in both men and women with type 1 or 2 diabetes.
- In contrast to trials in type 2 diabetes, most clinical trials evaluating exercise interventions in people with type 1 diabetes have not demonstrated a beneficial effect of exercise on glycemic control.
Benefits of Resistance Exercise
- A number of studies have shown that resistance training, using weight machines and/or free weights, improves glycemic control (reduced glycated hemoglobin [A1C]), decreases insulin resistance, increases muscular strength in adults with type 2 diabetes, and increases lean muscle mass and bone mineral density, leading to enhanced functional status and prevention of sarcopenia and osteoporosis.
Benefits of Other Types of Exercise
- To date, evidence for the beneficial effects of other types of exercise (e.g. yoga) is not as extensive or as supportive as the evidence for aerobic and resistance exercise.
Supervised vs. Unsupervised Exercise
- A systematic review and meta-analysis found that supervised programs involving aerobic or resistance exercise improved glycemic control in adults with type 2 diabetes, whether or not they included dietary co-intervention. Unsupervised exercise only improved glycemic control if there was concomitant dietary intervention.
- A 1-year randomized trial comparing exercise counselling plus twice-weekly supervised aerobic and resistance exercise vs. exercise counselling alone in patients with type 2 diabetes and the metabolic syndrome demonstrated greater reductions in A1C, blood pressure, body mass index, waist circumference and estimated 10-year cardiac risk, and greater increases in aerobic fitness, muscle strength and HDL-C among those enrolled in supervised exercise.
- Structured exercise programs supervised by qualified trainers should be implemented when feasible for people with type 2 diabetes to improve glycemic control, CVD risk factors and physical fitness [Grade B, Level 2].
Minimizing Risk of Exercise-Related Adverse Events
- For most people with and without diabetes, being sedentary is associated with far greater health risks than physical activity.
- People with diabetes with possible CVD or microvascular complications of diabetes who wish to undertake exercise that is substantially more vigorous than brisk walking should have medical evaluation for conditions that might increase exercise-associated risk. The evaluation would include history, physical examination (including funduscopic exam, foot exam, and neuropathy screening), resting ECG and, possibly, exercise ECG stress testing [Grade D, Consensus].
- Preproliferative or proliferative retinopathy should be treated and stabilized prior to commencement of vigorous exercise.
- People with severe peripheral neuropathy should be instructed to inspect their feet daily, especially on exercise days, and to wear appropriate footwear.
- Although previous guidelines stated that persons with severe peripheral neuropathy should avoid weight-bearing activity, recent studies indicate that they may safely participate in moderate weight-bearing exercise provided they don’t have active foot ulcers.
- Studies also suggest that daily weight-bearing activity decreases the risk of foot ulceration.
- The risk of hypoglycemia during exercise is of concern for people with type 1 diabetes and, to a lesser extent, in those with type 2 diabetes using insulin or insulin secretagogues (sulfonylureas and meglitinides).
- In these individuals, if pre-exercise blood glucose levels are <5.5 mmol/L, approximately 15 to 30 g carbohydrate should be ingested before exercise. (The actual amount will be dependent on injected insulin dose, exercise duration and intensity, and results of blood glucose monitoring).
- In individuals whose diabetes is controlled by lifestyle or oral hypoglycemic agents that do not increase insulin levels, the risk of developing hypoglycemia during exercise is minimal. Most individuals will not need to monitor their blood glucose levels or be required to supplement with carbohydrate for exercise lasting <1 hour.
In individuals with type 1 diabetes who are severely insulin deficient (e.g. due to insulin omission or illness), hyperglycemia can be worsened by exercise.
- In patients with type 1 diabetes, if capillary glucose is >16.7 mmol/L and the patient does not feel well, blood or urine ketones should be tested. If ketone levels are elevated, it is suggested that vigorous exercise be postponed and the patient take additional insulin.
- If ketones are negative and the patient feels well, it is not necessary to defer exercise due to hyperglycemia.
- Individuals with type 2 diabetes generally do not need to postpone exercise because of high blood glucose, provided they feel well. If capillary glucose levels are elevated >16.7 mmol/L, it is important to ensure proper hydration and monitor for signs and symptoms (e.g. increased thirst, nausea, etc.), especially if exercising in heat.
Minimizing Risk of Heat-Related Illness
- Patients with diabetes, especially those who are elderly and/or have autonomic neuropathy, cardiac or pulmonary disease, are at higher risk for heat illness.
- Metabolic, cardiovascular and neurological dysfunctions associated with diabetes, along with associated health issues and advanced age, reduce the body's ability to detect heat and impair its capacity to dissipate heat. Reductions in sweating and skin blood flow decrease the body's ability to maintain core temperature at safe levels, especially during extended heat exposure and/or exercise in the heat.
- Where possible, exercise should be performed in a cool environment or at times when the sun is not as its peak.
Acute Effects of Exercise on Blood Glucose
- During and after all but the most intense exercise, blood glucose tends to decline due to increased glucose disposal and insulin sensitivity.
- During, and especially after, brief, very intense exercise (e.g. competitive track and field, hockey, basketball, etc.), blood glucose often increases as a result of increases in glucose production that exceed increases in glucose disposal. This can make managing blood glucose levels challenging, particularly in patients with type 1 diabetes.
Exercise Prescription Details
- People with diabetes should accumulate a minimum of 150 minutes of moderate- to vigorous-intensity aerobic exercise each week, spread over at least 3 days of the week, with no more than 2 consecutive days without exercise [Grade B, Level 2, for type 2 diabetes; Grade C, Level 3, for type 1 diabetes].
- Walking is often the most popular and feasible type of aerobic exercise in overweight, middle-aged and elderly people with diabetes.
- For those who struggle with pain upon walking (e.g. due to osteoarthritis), semirecumbent cycling may provide an alternative.
- For most middle-aged individuals, moderate brisk walking on level ground or semirecumbent cycling would be an example of moderate aerobic exercise, while brisk walking up an incline or jogging would be vigorous aerobic exercise.
- People with diabetes (including elderly people) should perform resistance exercise at least twice a week and preferably 3 times per week [Grade B, Level 2] in addition to aerobic exercise [Grade B, Level 2]. Initial instruction and periodic supervision by an exercise specialist are recommended [Grade C, Level 3].
- Individuals with diabetes should also be recommended to reduce the amount of time spent doing sedentary activities.
Physical Activity in Children with Type 2 Diabetes
- A recent systematic review found no good-quality studies directly assessing the effects of physical activity in youth with type 2 diabetes.
- In the absence of direct evidence in this population, it is recommended that children with type 2 diabetes strive to achieve the same activity level recommended for children in general: 60 minutes daily of moderate to vigorous physical activity and limit sedentary screen time to no more than 2 hours per day.
Canadian physical activity guidelines for children and youth are available from the Canadian Society for Exercise Physiology (www.csep.ca).
Beginning Exercise in People with Low Baseline Fitness Levels
- Previously sedentary individuals with limited exercise tolerance may have to gradually build up their amount of exercise, starting with as little as 5 to 10 minutes per day.
- Multiple, shorter exercise sessions (each lasting at least 10 minutes) in the course of a day should be considered as this regimen is as effective as a single longer session of equivalent length and intensity.
Exercise in Type 1 Diabetes
- Moderate intensity aerobic exercise causes increased insulin sensitivity during, and for many hours after, activity in people with and without diabetes.
- In type 1 diabetes, there is little or no endogenous insulin secretion and no physiological regulation of insulin levels. If exogenous insulin and/or carbohydrate ingestion is not adjusted, hypoglycemia often occurs.
- Fear of hypoglycemia is an important barrier to exercise in people with type 1 diabetes and advice on physical activity to patients with type 1 diabetes should include strategies to reduce risk of hypoglycemia.
- Small studies have identified strategies that can be used alone or in combination for the prevention of hypoglycemia in type 1 diabetes:
- Consumption of extra carbohydrates for exercise, limiting preprandial bolus insulin doses and altering basal insulin for insulin pump users.
- Intermittent, very brief (10 seconds) maximal-intensity sprints either before, after or intermittently during an exercise session.
- Resistance exercise immediately prior to aerobic exercise.
- Exercise performed late in the day or in the evening can be associated with increased risk of overnight hypoglycemia in people with type 1 diabetes.
- To reduce this risk, one can reduce bedtime intermediate or long-acting injected insulin dose, or reduce overnight basal insulin infusion rates by approximately 20% from bedtime to 3 AM for insulin pump users.
- Hyperglycemia can occur after very intense exercise. If it occurs, it can be addressed by giving a small bolus of a short-acting insulin analogue or, in insulin pump users, by temporarily increasing the basal insulin infusion until euglycemia is restored.
Motivating People with Diabetes to Be Physically Active
- Physicians and other healthcare professionals can heighten awareness of the importance of physical activity by promoting regular exercise as a key component of therapy and identifying resources in the community.
- People with diabetes should set specific physical activity goals, anticipate likely barriers to physical activity (e.g. weather, competing commitments), develop strategies to overcome these barriers [Grade B, Level 2] and keep records of their physical activity [Grade B, Level 2].
- Having social support (e.g. exercising with a friend or partner) facilitates regular physical activity, especially for women.
- In youth with type 1 diabetes, physical activity adherence levels can be increased through structured programs involving pedometers, text messaging, social media and exercise trainers.
|Definition and recommended frequency||Intensity||Examples|
|Rhythmic, repeated and continuous movements of the same large muscle groups for at least 10 minutes at a time||Moderate:
50%-70% of person's maximum heart rate
|Recommended for a minimum of 150 minutes per week (moderate intensity)||Vigorous:
>70% of person's maximum heart rate
Activities of brief duration involving the use of weights, weight machines or resistance bands to increase muscle strength and endurance
Three times per week
Start with 1 set using a weight with which you can perform 15 to 20 repetitions while maintaining proper form.
Progress to 2 sets and decrease the number of repetitions to 10–15 while increasing the weight slightly. If you cannot complete the required repetitions while maintaining proper form, reduce the weight.
Progress to 3 sets of 8 repetitions performed using an increased weight, ensuring proper form is maintained.
Exercise with weight machines
Exercise with free weights
|Initial instruction and periodic supervision are recommended.
Note: the evidence supporting exercise with resistance bands is not as strong as the evidence for free weights or weight machines.
For definitions of the levels of evidence cited in this chapter, please refer to the Guideline Recommendations: Levels of Evidence.
If you would like more details on this topic, including references, please visit the Canadian Diabetes Association Clinical Practice Guidelines: Chapter 10.