Exercise management in type 1 diabetes: a consensus statement.

TL;DR: This Review provides an up-to-date consensus on exercise management for individuals with type 1 diabetes who exercise regularly, including glucose targets for safe and effective exercise, and nutritional and insulin dose adjustments to protect against exercise-related glucose excursions.

About: This article is published in The Lancet Diabetes & Endocrinology.The article was published on 2017-05-01 and is currently open access. It has received 466 citations till now. The article focuses on the topics: Aerobic exercise & Exercise physiology.

Summary

Introduction

• Management of type 1 diabetes remains challenging.
• In a large cross-sectional study of 18 028 adults with type 1 diabetes,3 patients who were categorised as being most physically active (exercising two or more times per week) had better HbA1c concentrations, a more favourable BMI, less dyslipidaemia and hypertension, and fewer diabetesrelated complications (retinopathy and microalbuminuria), than those who were less habitually active.
• The basic categories of exercise are described from a physiological perspective, as are the starting points for nutritional and insulin dose adjustments to keep patients in a targeted glycaemic range.

Modalities of exercise

• An understanding of the metabolic and neuroendocrine responses to the various types of exercise done by people with type 1 diabetes is essential for determination of appropriate nutritional and insulin management strategies.
• Exercise is generally classified as aerobic or anaerobic, depending on the predominant energy systems used to support the activity, although most exercise activities include a combination of energy systems.
• Resistance training is a type of exercise using free weights, weight machines, body weight, or elastic resistance bands that rely primarily on anaerobic energy-producing systems.
• High intensity interval training involves alternation between brief periods of vigorous exercise and recovery at low to moderate intensity (eg, from 20 s to 4 min intervals of exercise and rest, for up to ten cycles).
• 18 In some studies, high intensity interval training has been shown to be more effective than continuous aerobic training in improvement of cardiovascular fitness and various parameters related to glucose metabolism, including insulin sensitivity and glycaemic control in type 2 diabetes.

Individuals without diabetes

• The metabolic responses to different forms of exercise are distinct.
• 32 Increased 25 30 35 40 45 50 55 insulin concentrations in the circulation during exercise promote increased glucose disposal relative to hepatic glucose production, and might delay lipolysis—another feature that increases the reliance of muscles on glucose as a fuel.
• The risk of hypoglycaemia is elevated for at least 24 h in recovery from exercise, with the greatest risk of nocturnal hypoglycaemia occurring after afternoon activity.
• Exercise goals and glycaemic targets Individuals with type 1 diabetes should engage in exercise for various health reasons.

Elevated ketones

• The cause of elevated ketone concentrations should be identified (illness, diet manipulation, a recent bout of prolonged exercise, insulin omission, etc).
• Prolonged endurance type activities (eg, marathons and trekking) and diets very low in carbohydrate can elevate blood ketone concentrations in patients.
• Blood ketone concentrations of 3·0 mmol/L or more should be managed immediately by a qualified health-care professional (eg, a hospital emergency department or physician).

Recent hypoglycaemia

• Severe hypoglycaemia (defined here as blood glucose ≤2·8 mmol/L or a hypoglycaemic event requiring assistance from another individual) within the previous 24 h is a contraindication to exercise, because of the substantially increased risk of a more serious episode during exercise.
• Blood glucose at the start of exercise must also be viewed within a wider context.
• Factors to consider include directional trends in glucose and insulin concentrations, patient safety, and individual patient preferences based on experience.
• If blood ketones are elevated (≥1·5 mmol/L), exercise is contraindicated and glucose management should be initiated rapidly as per the advice of the health-care professional team.

Diabetes-related complications

• Overall, the health benefits of being physically active outweigh the risks of being sedentary for people with diabetes.
• Those with complications can derive several health benefits from low intensity physical activities, with little risk of any adverse events.
• In individuals with long-standing disease or with HbA1c concentrations well above the target, vigorous exercise, activities involving lifting of heavy weights, and competitive endurance events are contraindicated, particularly if the patient has unstable proliferative retinopathy, severe autonomic dysfunction, or renal failure.
• They should also be advised to wear or carry some form of diabetes identification.

Goals for nutritional management

• Nutritional management for people with type 1 diabetes should incorporate strategies that optimise glycaemic control while promoting long-term health.
• Application of these strategies to people with type 1 diabetes must consider the individual’s insulin management plan and include specific advice focused on nutrition for both athletic performance and glycaemic management.
• Daily carbohydrate intake should relate to the fuel cost of training in the athletic subpopulation and ensure prevention of hypoglycaemia for all active people.
• 66 Total energy requirements differ with individual aims.
• The first time a table, panel, or figure is mentioned in the text, any references in the table or figure that have not already been mentioned in the text should go into the reference list at that point, not at the end; refs 111 and 112 will therefore be moved here and cited after ref 71], also known as [A.

Nutritional needs for recovery

• Nutrition requirements to maximise muscle recovery and muscle protein synthesis after exercise have been well studied in the athletic population without diabetes.
• For replenishment of glycogen content after exercise, carbohydrate intake is essential.63 Consumption of foods with a low glycaemic index before exercise could sustain carbohydrate availability and maintain euglycaemia, whereas consumption of meals and snacks with a high glycaemic index after exercise could enhance recovery.
• Please describe study population] showed better blood glucose responses during exercise than did consumption of a carbohydrate with a high glycaemic index, also known as [A.

Fluid replacement

• Adequate fluid intake before, during, and after exercise is necessary for prevention of dehydration and optimisation of performance.
• Sports beverages containing carbohydrate (6–8%) and electrolytes are useful for athletes with type 1 diabetes exercising for a longer duration; they are also useful as a hydration and fuel source for higher intensity exercise, and for prevention of hypoglycaemia.
• 34,78 However, overconsumption of these beverages can result in hyperglycaemia.
• A review on low carbohydrate high fat diets and sports performance in individuals without type 1 diabetes concluded that, despite increasing the ability of muscles to utilise fat over time, no evidence was available to suggest performance benefits.
• A concern with these diets is that they could impair the capacity for high-intensity exercise.80 Variation in carbohydrate intake (ie, periodisation throughout the training cycle according to fuel needs and performance) has been suggested by some researchers as a way to help promote adaptation of skeletal muscle to training.

Recommendations for management of glycaemia

• Blood glucose responses to the various forms and intensities of exercise show high variability between and within individuals .
• Glycaemic management is therefore based on frequent glucose monitoring, adjustments to both basal and bolus insulin dosing, and consumption of carbohydrates during and after exercise.
• These recommendations are intended to serve as a starting point for insulin adjustments and carbohydrate intake that can then be individualised .
• Clinical management strategies should be built around exercise types and individual aims, and implementation of these strategies should take into account the factors summarised in panel 2.

5) added here so that first mention of table 3 is not within a non-text item. Refs 113–123 (in panel 2) and ref 124 (in table 2) will be cited after ref 83.]

• Another strategy is to combine a 75% reduction of the bolus insulin dose before exercise with ingestion of a snack or meal with a low glycaemic index.
• This approach will not protect against hypoglycaemia if the exercise is performed an hour or more after consumption of the snack.

Basal insulin approaches

• Late postprandial hypoglycaemia (>4 h after a meal) following aerobic exercise is driven partly by circulating basal insulin concentrations.
• For patients on multiple daily insulin injections, clinical observations and limited experimental data88 show that reduction of long-acting basal (as well as prandial) insulin concentrations before exercise reduces the risk of hypoglycaemia during and after the activity, but might promote hyperglycaemia at other points during the day.
• Such changes require adjustments in timing of basal insulin dose administration .
• Where practical, a basal rate reduction, rather than suspension, should be attempted 60–90 min before the start of exercise.

Exercise duration

• Few studies have tested various nutrient or insulin dose adjustments to prevent hypoglycaemia after exercise.
• The development of a fully artificial pancreas for exercise remains an elusive goal.

Conclusion

• Regular physical activity should be a routine objective for patients with type 1 diabetes, for various health and fitness reasons.
• Considerable challenges remain for people with type 1 diabetes, and their health-care team, in management of exercise and sports.
• Several small observational studies and a few clinical trials have been published to date that help to inform the consensus recommendations presented here.
• More studies are needed to determine how to best prevent exerciseassociated hypoglycaemia with basal rate insulin dose adjustments and how to manage glycaemia in the recovery period after exercise.
• Additional searches were done with the following terms for various subtopics within this Review: “nutrition”, “dietary carbohydrate”, “dietary protein”, “glycaemic index”, “hypoglycaemia”, “energy expenditure”, “glycaemic control”, “management”, “hypoglycaemia”, “hyperglycaemia”, or “prevention and control”.

Figures

Table 1: Carbohydrate requirements for endurance (aerobic) exercise performance and hypoglycaemia prevention

Figure 2: Decision tree for aerobic exercise and mixed aerobic and anaerobic activities lasting 30 min or longer in people with type 1 diabetes [A: correct?] This decision tree can serve as a starting point for individuals with type 1 diabetes [A: correct?] planning to do aerobic exercise. *Mixed activities that include anaerobic bursts of exercise might require a lower carbohydrate intake or lower [A:OK?] insulin dose reductions than continuous moderate aerobic activities. †If both resistance and aerobic exercise are to be done, resistance exercise could be done first to help attenuate hypoglycaemia. ‡In some situations, such as… [A: please complete], increased carbohydrate feeding rather than insulin dose reduction might help improve endurance performance in prolonged activities. In other situations, both bolus and basal insulin dose reductions might be needed to help restrict or reduce carbohydrate intake. [A: OK as edited?] Continuous glucose monitoring could be considered where patient or parent preference dictates, or in individuals with a history of nocturnal or severe hypoglycaemia. CSII=continuous subcutaneous insulin infusion. [A: what does the red asterisk correspond to?]

Table 2: Therapeutic adjustment options (in insulin or food intake, or both) to minimise glycaemic excursions for prolonged aerobic exercise and brief high intensity aerobic and anaerobic exercise

Figure 1: Variability in blood glucose responses to different forms of exercise [A: in people with type 1 diabetes?] High individual variability exists in the blood glucose responses to different form of exercise, as denoted by the arrows and grey shading. In general, aerobic exercise decreases glycaemia, anaerobic exercise increases glycaemia and mixed activities are associated with glucose stability. Individual responses are dependent on various additional factors, including the duration and intensity of the activity, initial blood glucose concentrations, individual fitness, concentrations of insulin, glucagon, and other counter-regulatory hormones in the circulation, and the nutritional status of the individual.

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Exercise management in type 1 diabetes: a consensus statement" ?

Regular exercise is important, but management of different forms of physical activity is particularly difficult for both the individual with type 1 diabetes and the health-care provider. This Review provides an up to date consensus on exercise management for individuals with type 1 diabetes who exercise regularly, including glucose targets for safe and effective exercise, and nutritional and insulin dose adjustments to protect against exercise-related glucose excursions. In a large cross-sectional study of 18 028 adults with type 1 diabetes, patients who were categorised as being most physically active ( exercising two or more times per week ) had better HbA1c concentrations, a more favourable BMI, less dyslipidaemia and hypertension, and fewer diabetesrelated complications ( retinopathy and microalbuminuria ), than those who were less habitually active. In general [ A: as you still refer to reference 3, would ‘ The study also showed that. Getting this much exercise is difficult for many patients ; results from a large cross-sectional study showed that [ A: insertion ok ? ] less than 20 % of patients manage to do aerobic exercise more than two times per week, and about 60 % of patients do no structured exercise at all. Regular exercise should be encouraged and supported by health-care professionals for many reasons, but primarily because the overall cardiometabolic benefits outweigh the immediate risks if certain precautions are Lancet Diabetes Endocrinol 2017 [ A: please check all affiliations carefully, provide highest degree for all authors, and indicate any full professors ] 

Q2. What are the benefits of sports drinks for people with type 1 diabetes?

Sports beverages containing carbohydrate (6–8%) and electrolytes are useful for athletes with type 1 diabetes exercising for a longer duration; they are also useful as a hydration and fuel source for higher intensity exercise, and for prevention of hypoglycaemia. 

Q3. What are the main determinants of glucose production during aerobic exercise?

Although the main determinant of glucose production during aerobic exercise is an increase in glucagon concentrations, neural control of glucose release and other counter-regulatory hormones also have a supportive role. 

Q4. What is the effective way to promote adaptation of skeletal muscle to training?

80Variation in carbohydrate intake (ie, periodisation throughout the training cycle according to fuel needs and performance) has been suggested by some researchers as a way to help promote adaptation of skeletal muscle to training. 

Q5. What is the drink for low-intensity and short-duration sports?

Water is the most effective drink for low-intensity and short-duration sports (ie, ≤45 min), as long as glucose concentrations are 7 mmol/L or higher. 

Q6. What is the way to reduce basal insulin concentrations before exercise?

For patients on multiple daily insulin injections, clinical observations and limited experimental data88 show that reduction of long-acting basal (as well as prandial) insulin concentrations before exercise reduces the risk of hypoglycaemia during and after the activity, but might promote hyperglycaemia at other points during the day. 

Q7. What is the common type of exercise associated with a decrease in glucose concentrations?

In general, aerobic exercise is associated with reductions in glycaemia, whereas anaerobic exercise might be associated with a transient increase in glucose concentrations. 

Q8. What is the way to improve the health of people with type 1 diabetes?

Body composition, cardiorespiratory fitness, endothelial function, and blood lipid profile (ie, triglycerides and total cholesterol) all improve with regular physical activity in children and young people with type 1 diabetes. 

Q9. What is the way to prevent exercise-associated hypoglycaemia?

Threshold suspension of insulin delivery in continuous subcutaneous insulin infusion could offer additional protection against exercise-associated hypoglycaemia, according to some data. 

Q10. What should be done to prevent a recurrence of a ketone?

Blood ketone concentrations of 3·0 mmol/L or more should be managed immediately by a qualified health-care professional (eg, a hospital emergency department or physician). 

Q11. What can promote increase in glycaemia after exercise?

As mentioned above, weight lifting, sprinting, and intense aerobic exercise can promote increase in glycaemia that could last for hours in recovery. 

Q12. What is the primary goal of ePARmed-X+?

By contrast, if maximisation of sports and exercise performance is the primary goal, then nutritional For more on ePARmed-X+ and PAR-Q+ see http://eparmedx.com1 

Q13. What are the common ways to manipulate carbohydrate availability?

81 Additionally, various exercise-nutrient protocols are used to manipulate carbohydrate availability, such as training in a fasting state or withholding carbohydrate intake at a meal before or after exercise. 

Q14. How much energy do athletes need to meet the demands of their daily activities?

63,65Daily energy and macronutrient balance Athletes with type 1 diabetes need sufficient energy to meet the demands of their daily activities. 

Q15. How many minutes of exercise per week is recommended for adults with diabetes?

For all adults living with diabetes, including those living with type 1 diabetes, 150 minutes of accumulated physical activity is recommended each week, with no more than two consecutive days of no physical activity [A: please give a reference for this sentence]. 

Q16. What are the common types of exercise readiness questionnaires?

Exercise readiness questionnaires, such as Physical Activity Readiness Medical Examination (ePARmed-X+) and Physical Activity Readiness Questionnaire for Everyone (PAR-Q+), are available online for adults with diabetes who might be at increased risk of developing adverse events. 

Q17. What is the way to prevent hypoglycaemia?

Concentrations higher than 7–10 mmol/L might be acceptable in some situations where added protection against hypoglycaemia is needed. 

Q18. What is the risk of recurrence of a blood glucose relapse?

In situations where minor hypoglycaemia (blood glucose 2·9–3·9 mmol/L, with the ability to self-treat) has occurred, the increased risk of recurrence must be taken into account.60 VigilancePanel 1: Blood glucose concentrations before exercise commencement and recommended glucose management strategies