Diabetes and Exercise- #ISPAD2021 S1E2

 

Exercise Management Requires an Understanding of not only “How?”, but “Why” (and the ability to communicate this to youth)  

Goals- participation, health, fitness, spontaneity, fun!

Essential Message on Exercise for Youth with T1D:

1.    Activity recommendations for children and adolescents with diabetes are the same as the general population.

60 minutes/day, mix of moderate and vigorous, aerobic and weight-bearing/strengthening activity (minimum of 3days/week)

2.    Achieving recommended levels of physical activity may be difficult due to disease complexity

3.    Specific barriers can usually be overcome with appropriate education and training.

What do we need to know to manage patients and help them manage themselves?

1.    All exercise is not the same

2.    Teach the physiology of Exercise

3.    Address barriers and knowledge gaps

4.    Offer practical strategies

Barriers to Exercise

1.    Lack of knowledge:

Patients needs education; need to reach out to sports coaches; Health care professionals

2.    Effect of Blood Glucose Level (BGL) on exercise

Performance?

3.    Effect of exercise on Blood Glucose Level (BGL):

Hypoglycemia; hyperglycemia; unpredictability

4.    Psychosocial:

Fear of hypos; need for extra support; self esteem

5.    Not related to T1DM:

Motivation; time; resources

Barriers to exercise participation

·         Teenage girls with T1DM are less active than teenage boys (in general), and less active than girls of the same age without diabetes

·         Fear of hypoglycemia historically reported as a barrier to exercise in T1DM...

Practical suggestions for active people with T1D

Hydration

·         Essential to performance

·         Use electrolyte tablets/powders if needed

·         Easy form of measurable and quickly digestible carbohydrates (for replacement) during exercise

·         Maintaining CGM accuracy

CGM/infusion set adhesion/issues

·         Much more difficult during exercise of long duration or in humid climate (due to sweaty skin)

·         Change sites/sets 1 day prior to competition

·         Use additional adhesives as necessary (Tegaderm, Mastisol)

Exercise Physiology

NB. This is insulin-independent process

·         Exercise (muscle contraction) stimulates glucose movements from the blood stream into the muscle cell

·         At rest we have a pour of glucose transporters (called GLUT4) within the muscle cell and a pour of glycogen

·         A small amount of glucose in blood enters passively into the cell, as primarily stored in the form of glycogen

·         However, at the onset of exercise we have increased blood flow and the stored fuels (glycogen), which fuels the initial muscular contraction and this produces the glucose transporters to the muscle membrane.

·         This facilitates further facilitated diffusion of glucose from the blood stream into the muscle cell, which then further fuels Glycolysis (the process in which glucose is broken down to produce energy) and Adenosine triphosphate (ATP) production (the source of energy for use and storage at the cellular level) and further muscle contraction

·         As exercise continues, there’s further depletion of glycogen stores and increased translocation of GLUT4 transporters to the muscle cell

Insulin then further augments GLUT4 translocation and glucose uptake

Insulin Resistance in Youth with T1D

·         Youth with T1D have been seen to have   insulin resistance on par with obese individuals

·         This insulin resistance is associated with adverse cardiovascular outcomes and also associated with adverse physical fitness in Type 1 Diabetes

·         Insulin sensitivity is one of the benefits of exercise intervention

·         However, we are increasingly recognizing that the youth with type 1 diabetes have a degree of insulin resistance

Glucose Provision During Exercise Requires Glycogen Mobilisation

·         We have (70-80g) of glycogen available in the Liver, that is available to bloodstream to maintain blood glucose

·         We may have a much higher reservoir of (350-800g) glycogen in the muscle, available for muscular contraction but not available to restore blood glucose levels (we have of glycogen

·         Glycogen and liver glucose output is controlled by multiple hormone or inputs (including the balance between insulin and glucagon in the portal circulation and the level of other stress hormones such as catecholamines- (which increases glycogen breakdown) and gluconeogenesis (the process of transforming non-carbohydrate substances into glucose

·         Normally in the exercise setting and in the presence of a falling glucose, insulin is very quickly switched off in people without type 1 diabetes

·         People living with type 1 diabetes cannot turn their insulin level down, once the dosage has been given, and therefore there are oftenly exercising in a relatively hyperinsulinemic state where the amount of insulin in the blood is higher than what’s considered normal).

·         They also lose their glucagon responses to hypoglycemia overtime

·         The balance of insulin and glucagon in people with type 1 diabetes

Fuel Utilization: Glycogen/Fat Demand Changes with Intensity

·         The general principle here is a very low intensity will primarily burn fat (as an oxidated fuel source) whereas with high intensity will primarily burn glycogen in the form of muscle and a small component of plasma glucose    

·         Glycogen storage (the utilization of glycogen stores) increases with exercise intensity

NB. In people living with type 1 diabetes, they can maintain normal muscle and liver glycogen stores if there are doing well with tight glucose control and good insulin management

Glycogen levels lowered by poor glycaemic control, thus higher risk of hypoglycemia

A fueling Plan- Prepare where possible

·   High quality meal 3-4 hours prior- for glycogen stores

·         Try to avoid exercise with insulin on board (IOB)- bolus at least 2-3hours prior, otherwise bolus reduction is usually required

·         For high performance, more than 30minutes duration 30-60grams/hour for teenagers (limited by absorption and reduced Glycaemic index perfusion under high-stress conditions)

o   Maybe up to 90grams if 60grams of glucose and 30grams fructose are used in trained older youth, however, this is rare in children

·         Shorter duration or pure strength session likely requires ≤0.5 grams/kg if basal conditions only- otherwise hyperglycemia

Common Questions/Scenarios

1.    Blood glucose rise after exercise

o   Insulin deficit in the leading period or during exercise

o   Excessive fueling (more carbohydrate than was required)

o   Delayed absorption of carbohydrate in the gut (return of gut perfusion

o   Adrenergic surge and imbalance between glucose production and disposal (Glucose Uptake decreases quickly but there’s a persistent hormonal drive to breakdown glycogen and Glucose Production remains high), which ultimately leads to high blood glucose levels

 Strategies:

o   A cooldown method can be used (e.g. Walk/easy spin) to clear lactate and reduce glucose production

o   Very cautious correction- recommended starting with ½ usual correction dose

o   Avoiding prolonged insulin deficit

2.    What is the risk if Blood Glucose is high before exercise?

o   Performance does not necessarily suffer

o   Blood glucose may fall quickly anyway- often pre-exercise hyperglycemia in youth is due to exercise in the early post-prandial state (e.g. after lunch/afternoon tea)

o   Higher glucose may favor increased flux through GLUT4 into the muscle once exercise starts (“The higher they are, the harder they fall”)

o   Unless high ketones (>1.5 mmol/L) are probably ok to exercise, especially if aerobic or sensor trend is steady/downward- remember the goal is to get kids active, not to achieve perfection!

o   Clinical judgment- possible pump issue, missed insulin, acute illness, etc… Then safety first and avoid exercise at least until ketones cleared

3.    What can we recommend for those on BD/mixed insulin regimens?

o   Insulin sensitivity increases by around 20%

o   Can reduce evening dose or morning intermediate-acting by this amount

o   NPH (more variable insulin) has less predictable absorption and more variable dose-dependent peak duration, so difficult one!

o   Plan likely needs to focus primarily on glucose monitoring, and be carb focused to avoid hypoglycemia (much as is the case with spontaneous exercise)

o   NPH insulin peak is around 6hrs and lasts for 12-18hrs, school may occur on top of near peak insulin if it's given at 8am/breakfast time

o   Morning exercise likely easier to perform with basal analog from the evening before

o   If new to exercise and occurs after school, then reduce evening long-acting by 20%

4.    What Advice to give families following low-carb diets?

o   Low carb diets are not associated with improved exercise capacity

o   Risk of hypoglycemia during (and likely later in theory) due to glycogen depletion

o   Possible poor response to emergency glucagon

o   If fatigue is reported then suggest increased fueling during exercise (“Don’t diet on the bike”)

o   Role of the dietitian is key in information sharing, counseling, and assessment of growth/lipids  

Work through this Approach

In conclusion, Regular physical activity during childhood is important for optimal physical and psychological development. For individuals with Type 1 Diabetes (T1D), physical activity offers many health benefits including improved glycemic control, cardiovascular function, blood lipid profiles, and psychological well-being. Despite these benefits, many young people with T1D do not meet physical activity recommendations.

                           Acknowledgments to: Craig Taplin (Children's Diabetes Centre, Perth Children's Hospital, Telethon Kids Institute Western Australia)