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Regular physical activity (PA) plays a key role in the management of Type 1 diabetes mellitus (T1D).

This has been known for years as on the Joslin Victory Medal it is one of the three horses that controls Type 1 diabetes, the other being Insulin and diet.

 
Figure 1: Joslin Victory medal for living with T1DM
    
Figure 2 summaries what is known about the benefits of exercise in people with T1D . The known benefits include

•     improved insulin sensitivity
•     improved well-being
•     reduction in lipids
•     reduction in microvascular complications
•     reduced mortality

For further information see What are the health benefits of physical activity in type 1 diabetes mellitus? A literature review

Figure 2: Summary of health benefits of regular exercise in Type 1 diabetes.

Although there is as yet not conclusive evidence that regular exercise helps to preserve beta cell function there is some evidence to support this

 In mice susceptible to diabetes (NOD mouse) regular exercise prevents the development of diabetes. See Exercise Training but not Curcumin Supplementation Decreases Immune Cell Infiltration in the Pancreatic Islets of a Genetically Susceptible Model of Type 1 Diabetes

 The Type 1 diabetes honeymoon period is more than five times longer in men undertaking high levels of physical exercise, compared with age‐, sex‐ and BMI‐matched sedentary controls. See The Type 1 diabetes ‘honeymoon’ period is five times longer in men who exercise: a case–control study
In a pilot RCT of newly diagnosed patients with Type 1 diabetes there is some suggestion that exercise preserves beta cell function. See Exercise to preserve β‐cell function in recent‐onset Type 1 diabetes mellitus (EXTOD) – a randomized controlled pilot trial

Note that improvement in HbA1c is not listed as one of the benefits of exercise. A meta-analysis of studies carried out in 2013 by us did not demonstrate an improvement in HbA1c with regular exercise in adults and children with Type 1 diabetes. For more information about this see Does exercise improve glycaemic control in type 1 diabetes? A systematic review and meta-analysis

One reason for this could be that advice given to people with Type 1 diabetes around how to control glucose around exercise is not very good.

Recommended Levels of activity for people with Type 1 diabetes and barriers to exercise

Based on this evidence guidelines recommend that adults with Type 1 diabetes undertake at least 150 min per week of moderate to vigorous aerobic exercise, spread out over at least 3 days, with no more than two consecutive days between bouts of aerobic activity (see Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association and Physical activity levels of people with Type 1 diabetes.

Over 70% of people with Type 1 diabetes do not meet these recommendations and thus are not getting the full benefits they could do from exercise. (See Physical activity levels of people with Type 1 diabetes to learn more about recommended levels of activity for people with Type 1 diabetes and current activity levels of people with Type 1 diabetes.)

Reported barriers to exercise in those with Type 1 diabetes include fear of hypoglycaemia, competing work commitments, loss of control over diabetes, low fitness levels, cost, lack of social support, and lack of knowledge. Greater knowledge about insulin pharmacokinetics and using appropriate approaches to minimise exercise‐induced hypoglycaemia or hyperglycaemia are factors associated with fewer perceived barriers to exercise (see Barriers to exercise in people with Type 1 diabetes to learn more about barriers in Type 1 diabetes).This suggests that the provision of knowledge and skills is essential if we are to support people with Type 1 diabetes to become more active and enable them to exercise safely at the level they wish to.

Other parts of the website should help you to arm your patients with knowledge to overcome these barriers.

Articles linked to this article

Physical activity levels of people with Type 1 diabetes

Barriers to exercise in people with Type 1 diabetes.

Assessment of the patient

People with Type 1 diabetes tend to have four main problems when exercising these are;

•     problems controlling their blood glucose during and immediately following exercise
•     unexplained severe hypoglycaemia particularly at night
•     reduced performance due to excessive fatigue and reduced muscle strength.
•     difficulties gain or losing weight

It is important that a detailed history and examination is undertaken to deal with these issues.

Key things in History and examination

Current approaches to managing T1DM

•     Patients need to check their glucose regularly when exercising
  
•     Patients who carbohydrate count and use carb/insulin ratios have more options to manage their exercise.
•     High blood glucoses – make it difficult to build up muscle mass and glycogen stores post exercise so ideally HbA1c should be a good as possible.

Insulin regime

•     It is difficult to manage patients who are performing regular exercise on premixed twice-daily regimes without incurring the risk of exercise-induced hypoglycaemia.
•     Fast-acting insulin analogues (Insulin aspart (Novo Nordisk), lispro (Eli Lilly) or glulisine (Sanofi-Aventis)) have a shorter window of action than human, pork or beef insulin which can be helpful if exercising around meal times.
•     The longer duration of action of the long-acting basal insulins whilst helpful in routine clinical care, can result in higher insulin concentrations during exercise and an increased risk for hypoglycaemia during endurance exercise and less flexibility in reducing dose post exercise
•     In one clinical study NPH insulin (insulatard (Novo Nordisk), Humulin I (Eli Lilly)) and determir (Novo Nordisk) had lower risk of hypoglycaemia with exercise than glargine (sanofi-aventis)(see Plasma glucose and hypoglycaemia following exercise in people with Type 1 diabetes: a comparison of three basal insulins.)
•     In another study glargine had similar rate of hypoglycaemia after exercise as Degludec (Novo Nordisk). (see Similar risk of exercise‐related hypoglycaemia for insulin degludec to that for insulin glargine in patients with type 1 diabetes: a randomized cross‐over trial).
•     No studies to data have looked at Insulin glargine u300 (Toujeo – Sanofi-aventis) or Abasaglar (Biosimilar Glargine – lilly) and exercise in Type 1 diabetes.
•     Changes to insulin rates and background rates during and post exercise can be different to those on MDI regimes (see Pumps and exercise).

Insulin injection techniques

•     The aim to reduce day-to-day variation in insulin absorption and to avoid accelerated absorption of insulin when exercising.
•     Injection sites should be checked to ensure there is no lipohypertropy.
•     Injection techniques should be checked to ensure that air shots are being given. If the patient is on NPH insulin resuspension should be carried out correctly.
•     Needle sizes should also be checked - 4 or 5mm needles are to be recommended.
•     Patients should also be educated to avoid injecting into areas that will be used in planned exercise (eg. thighs before cycling) because the increased blood flow will increase insulin absorption.

Diabetes complications

•     For most people with T1DM any activity can be undertaken and risk is minimal if people start at a low intensity of activity and gradually build up the intensity.
•     Some diabetes complications restrict what people with T1DM, others suggest that further investigations should be done before exercise is started (see Exercise and microvascular complications and Exercise and macrovascular complications).
•     Feet will need to be examined to look for: ulceration, deformity and evidence of neuropathy.
•     Eye report/photos should be looked at so assess whether the patient has retinopathy if so what level.

Review of calorie intake

•     Ensuring adequate fuel and fluid replacements is one of the most important components in ensuring safe and effective training in people with Type 1 diabetes.
•     A common cause of hypoglycaemia and of fatigue during and following exercise is simply one of insufficient calorie intake.
•     For these reason, all patients should have their dietary intake assessed if doing more than 1 hour a day of moderate intensity exercise. Ideal this should be done by a dietician.
  

A detailed history of exercise program

•     The type, duration and intensity of exercise will determine blood glucose fluxes both during and after exercise. Endurance events will tend to lower glucose (see Types of exercise and their effects on blood glucose.)
•     Anaerobic or intense exercise will tend to increase glucose during and on occasions after exercise (See Types of exercise and their effects on blood glucose).
•     This knowledge will influence the advice provided on what to do with starting glucoses (see Blood glucose and exercise for adults with T1D).
•     Similarly, this knowledge may influence the advice given on carbohydrate intake (Carbohydrates for exercise for people on multiple daily injections and Carbohydrate for exercise for people on insulin pumps) and insulin therapy.

History of performance in training and competition

•     The approach to glucose management (for example the starting blood glucose) may need to be different in training and competitive events (seeBlood glucose and exercise for adults with T1D).
•     Exploring performance in these two settings will enable the optimal approach to be designed for each of these settings

Articles linked to this article

Exercise and microvascular complications

Exercise and macrovascular complications

Fuel and fluid for exercise

Types of exercise and their effects on blood glucose

Blood glucose and exercise for adults with T1D

Carbohydrates for exercise for people on multiple daily injections

Carbohydrate for exercise for people on insulin pumps

In simple terms there are three ways that glucose can be managed during exercise. The easy way to remember these is through the mnemonic ‘ICE’.

I Insulin adjustment

C Carbohydrate for exercise

E Exercise - changing type or intensity

Insulin adjustment for exercise

The liver is main source for carbohydrate that is used when exercising. When insulin levels are high, the liver is prevented from releasing glucose (see glucose control during exercise). High insulin levels during exercise could therefore lead to a mismatch between the glucose produced by the liver and that used by the muscles. This will result in a fall in circulating blood glucose falling during exercise.

Ideally patients should exercise with as little insulin around as possible. Changes can be made to the quick-acting (bolus) or the background (basal) insulin to help with this. What changes are made to insulin will depend on the type, intensity and length of the exercise and on what time of day the exercise is carried out.


Carbohydrate for exercise

The two main fuels used during exercise are fats and carbohydrates (in the form of glucose). People with Type 1 Diabetes burn fat normally during exercise; it is only the production of carbohydrate that they have problems with.
The exercise carbohydrate value of an exercise is the amount of carbohydrate that is used during an exercise. The higher the exercise’s intensity, the more carbohydrate is burned per minute see figure 1 below.

The amount of carbohydrate needed will also depend on the age, sex, weight and fitness of the person performing the exercise.

When using carbohydrates for exercise, the aim is to take all the carbohydrate needed to perform the particular exercise so that the glucose remains stable across the exercise.

To find out more, go to Carbohydrates for exercise for people on multiple daily injections.

   
Exercise adjustment for exercise

Different exercise regimes have different effects on blood glucose concentration (see Types of exercise and their effects on blood glucose). This knowledge can be used to help control glucose during exercise. Changing the order in which exercise is done or adding a different type of exercise can help with glucose control during exercise.

To find out more about this go to exercise adjustments for exercise.

Summary

Each of these strategies has its pros and cons. The table below is a summary of the pros and cons. This may be helpful in deciding which strategy you choose to recommend first to your patients

Definition of exercise

Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. Physical activity in daily life can be categorized into occupational, sports, conditioning, household, or other activities. Exercise is a subset of physical activity that is planned, structured, and repetitive and has as a final or an intermediate objective the improvement or maintenance of physical fitness.

Exercise is performed for various reasons, to aid growth and improve strength, preventing aging, developing muscles and the cardiovascular system, honing athletic skills, weight loss or maintenance, improving health and also for enjoyment. For more details on the health benefits of exercise for people with Type 1 diabetes.

Guidelines recommend that adults with Type 1 diabetes undertake at least 150 min per week of moderate to vigorous aerobic exercise, spread out over at least 3 days, with no more than two consecutive days between bouts of aerobic activity. In addition, muscle-strengthening activities that involve all major muscle groups should be performed on two or more days per week. For more information on recommended levels of activity for people with Type 1 diabetes see Physical activity levels of people with Type 1 diabetes section of this website

Being able to define what type of exercise what type of exercise a patient does is key to understanding what will happen to their blood glucose when they perform that exercise. This will also help you to work out how much energy the patient will burn during that exercise and any changes you may need to suggest to their insulin regimen and eating patterns when performing that exercise.

The Pyramid of fitness

In simple terms, to improve at any type of exercise you need to work on four areas (see figure 1).

Figure 1 - the pyramid of fitness

How much someone needs to work on each of these will depend on what exercise they are doing.

Defining a patient’s exercise

Defining exactly what a patients does should form part of the initial assessment of a patient (see Initial medical assessment of patient with Type 1 diabetes in relation to exercise part of this website.

To give good tailored advice to a patient you will need to know determine three things:

1. What type of activity the patient is doing (click here to learn more about this)
2. How intense the activity is (click here to learn more about this)
3. How long the activity will last for (click here to learn more about this)

Once you have learned this you are ready to start to give advice on how your patient can manage glucose around exercise (see Encouraging patients to exercise and starting advice section of this website).

How much someone needs to work on each of these will depend on what exercise they are doing.

Defining a patient’s exercise

Defining exactly what a patients does should form part of the initial assessment of a patient (see Initial medical assessment of patient with Type 1 diabetes in relation to exercise part of this website.

To give good tailored advice to a patient you will need to know determine three things:

1. What type of activity the patient is doing (click here to learn more about this)
2. How intense the activity is (click here to learn more about this)
3. How long the activity will last for (click here to learn more about this)

Once you have learned this you are ready to start to give advice on how your patient can manage glucose around exercise (see Encouraging patients to exercise and starting advice section of this website).

Defining a patient’s exercise

Defining exactly what a patients does should form part of the initial assessment of a patient (see Initial medical assessment of patient with Type 1 diabetes in relation to exercise part of this website.

To give good tailored advice to a patient you will need to know determine three things:

1. What type of activity the patient is doing (click here to learn more about this)
2. How intense the activity is (click here to learn more about this)
3. How long the activity will last for (click here to learn more about this)

Once you have learned this you are ready to start to give advice on how your patient can manage glucose around exercise (see Encouraging patients to exercise and starting advice).

Recommended levels of activity

Shown below is the recommended levels of activity for adult, children and pregnant women with Type 1 diabetes.

How active are people with Type 1 DM

Most studies of physical activity (PA) levels in adults with Type 1 diabetes have been based on self-reported data rather than objective data. They all suggest that people with Type 1 diabetes are not very active.

Self-reported studies

• A retrospective analysis of the Diabetes and Complications Trial found 19% of (271/1441) participants were not achieving recommended PA levels (see - Effects of physical activity on the development and progression of microvascular complications in type 1 diabetes: retrospective analysis of the DCCT study).

• In the EURODIAB prospective cohort study of 2185 people with Type 1 diabetes from 16 European countries, 786 (36%) patients were doing no or only mild PA (see - Association of physical activity with all-cause mortality and incident and prevalent cardiovascular disease among patients with type 1 diabetes: the EURODIAB Prospective Complications Study).

• In the Finnish Diabetic Nephropathy Study, 23% of people with Type 1 diabetes were classed as sedentary and a further 21% were doing less than one session of exercise per week. (see - Physical Activity and Diabetes Complications in Patients With Type 1 Diabetes. The Finnish Diabetic Nephropathy (FinnDiane) Study).

• In a cross sectional study of 18028 patients with Type 1 diabetes in Germany and Austria 63% of participants reported doing no regular PA (see - Impact of Physical Activity on Glycemic Control and Prevalence of Cardiovascular Risk Factors in Adults With Type 1 Diabetes: A Cross-sectional Multicenter Study of 18,028 Patients).

Objectively measured PA

• In a Canadian study of adults with Type 1 diabetes only 43% of women and 55% of men with Type 1 diabetes were active (see - Physical activity level and body composition among adults with Type 1 diabetes).

• In a UK study of adults with Type 1 diabetes, adults with Type 1 diabetes undertook 37 mins per day of moderate to vigorous physical activity compared to 52.9 mins per day in healthy matched controls. (see - Objective Measurement of Physical Activity in Adults With Newly Diagnosed Type 1 Diabetes and Healthy Individuals).

The reasons for the reduced level of physical activity could be due to that additional barriers that people with Type 1 diabetes have to physical activity.

Patients with Type 1 diabetes have many barriers to exercise that are similar to the general populations such as

• Lack of time
• Work pressures
• Bad weather
• Cost
• Lack of motivation

But there are certain barriers that are specific to them, see table below.

Table showing barriers to physical activity in patients with Type 1 diabetes.

To be able to increase activity these barriers will have to be overcome.

For more information on this subject see

1. Brazeau A.S et al paper (Barriers to Physical Activity Among Patients With Type 1 Diabetes. Diabetes Care. 2008;31(11):2108-9).
2. Dubé MC et al paper (Development and validation of a new scale. Diabetes Research and Clinical Practice. 2006;72(1):20-7).
3. Lascar N et al paper (Attitudes and Barriers to Exercise in Adults with Type 1 Diabetes (T1DM) and How Best to Address Them: A Qualitative Study).
4. Kennedy A et al paper (Attitudes and barriers to exercise in adults with a recent diagnosis of type 1 diabetes: a qualitative study of participants in the Exercise for Type 1 Diabetes (EXTOD) study).