Physical Activity in Children and Adolescents with Type 1 Diabetes

Abstract

This chapter explores the multifaceted role of physical activity in type 1 diabetes management during childhood and adolescence. In addition to improved cardiovascular and metabolic health typically associated with physical activity, there are several diabetes-specific benefits of regular activity. For example, improved insulin sensitivity in insulin sensitivity that may be particularly important for children with type 1 diabetes approaching puberty when insulin resistance is known to increase, especially in females. Similarly, there are important diabetes-specific metabolic differences in response to physical activity that require consideration for blood glucose excursion management. Type, duration, and intensity of activity influence metabolic response in type 1 diabetes. For example, during aerobic activity, skeletal muscle glucose uptake increases to generate energy for muscle contraction, which suppresses hepatic gluconeogenesis and thus promotes a decrease in blood glucose levels and increased risk of hypoglycaemia. Intermittent, intense, or anaerobic activity can induce transient and often dramatic hyperglycaemia due to the release of the hormones epinephrine and glucagon. This rise in blood glucose can be followed by hypoglycaemia in the hours after activity. Within this chapter, the need for individualised and informed planning for safe participation in PA and exercise for children and adolescents is explored.

1. Introduction

The global incidence of Type 1 Diabetes (T1D) in children is increasing; reports suggest that approximately 79,000 children develop T1D annually [1, 2]. T1D is a common, chronic, life-long illness with multifaceted considerations for the physical, psychological, and social implications associated with living with the condition [1]. For example, T1D is associated with increased risk of cardiovascular disease, neuropathy, and retinopathy. Similar to adult populations, the goal of T1D management in children is to promote health, maintain function, and to either prevent or delay adverse health outcomes, such as micro- and macrovascular changes, diabetic ketoacidosis, and renal impairment [3, 4, 5].

Insulin is the mainstay of management for T1D [2], non-pharmacological interventions that promote positive clinical, psychological, and social outcomes for chronic disease management have been recognised as an important addition to pharmacological management. Notably, physical activity (PA) is an important adjunct to insulin and dietary management for T1D [2, 3, 4, 5, 6, 7, 8]. 60 min of moderate to vigorous physical activity (MVPA) and limited sedentary time is recommended by The World Health Organization (WHO) for children to sustain health.

For healthy populations, there is a substantial amount of scientific evidence promoting the physical and psychological health benefits associated with living a physically active lifestyle [3, 4, 5, 6, 7]. PA has been associated with improvements in cardiovascular function, bone density, bone strength, musculoskeletal conditioning, blood pressure, insulin sensitivity, and blood lipid profiles [3, 4, 5, 6, 7]. PA also reduced the risk of comorbidities associated with sedentary lifestyles [3, 4, 5, 6, 7]. Consequently, promotion of PA with the aim of increasing PA engagement and reducing sedentary behaviour is the focus of the World Health Organization’s global plan on PA (2018–2030) [3]. During childhood and adolescence, the experience of PA can shape future PA decisions and PA behaviours throughout later life [2, 3, 4, 5, 6, 7]. Thus, it seems imperative and logical that early intervention promotes PA engagement in childhood and a pertinent component of diabetes management [3].

Individuals living with chronic illness or disability are at risk of not meeting PA recommendations due to limited safe, appropriate, and supportive PA initiatives to meet their additional needs. Unfortunately, children and adolescents with T1D often do not meet the WHO recommended PA targets. Despite the potential benefits of PA engagement [2, 3, 4, 5, 6, 7], figures suggest that children with T1D are not meeting the recommended daily PA requirements to sustain health. PA engagement for children with T1D requires careful management of blood glucose excursions [2, 3, 4, 5, 6, 7] and T1D populations face significant, disease-specific barriers to PA engagement.

Notably, most guidelines currently available for the support and promotion of PA in children and adolescents with type 1 diabetes are based on physiological knowledge and evidence derived from adult clinical studies. Further research is required to deepen our knowledge and understanding of PA in paediatric populations thus any exercise prescription or management plan should be individualised with prior experience and safety at the fore. Although medical complications are rare, medical clearance and guidance should be sought to support coaches and parents in determining any restrictions that may be relevant. For example, individuals who have proliferative retinopathy or nephropathy should avoid resistance-based exercise or anaerobic exercise that results in high arterial blood pressure.

For the purposes of this chapter, the terms PA, sport, and exercise are used interchangeable, however, PA typically refers to unstructured physical exertion. In contrast, sport and exercise typically refers to planned and structure activity that may include team or individual pursuits. PA, sport, and exercise can be further categorised depending on the nature of the activity and energy systems utilised. Throughout this chapter aerobic and anaerobic activities are discussed. Aerobic activity (e.g. walking, distance running) utilises oxygen and the cardiovascular system to provide energy to sustain the activity. Anaerobic activity (e.g. weight lifting, sprinting) is any activity that breaks down glucose for energy without using oxygen instead using lactic or alactic energy metabolism pathways.

2. Physiological principles of physical activity and diabetes

It is well established that PA and exercise are associated with numerous physiological benefits for sustaining health [2, 3, 4, 5, 6, 7]. However, PA also presents a physiological and metabolic stressor that disrupts glycaemic balance and requires careful regulation to maintain homeostasis. To begin exploring the role of PA and exercise in type 1 diabetes management for children, it is important to consider the physiological differences (and similarities) in hormonal regulation at play. In healthy individuals, endogenous hormonal feedback and feedforward mechanisms underpin the maintenance of tightly controlled blood glucose levels. The hormone responsible for reducing blood glucose levels is insulin. There are several hormones that are responsible for increasing blood glucose levels in the body (e.g. glucagon, epinephrine, norepinephrine). During exercise, pancreatic beta cell production of insulin is suppressed, and pancreatic alpha cell production of glucagon is upregulated to manage the systemic supply of glucose in response to the physiological demands of the exercise or activity being undertaken. Muscle contraction also upregulates blood glucose transport into cells resulting in a counter regulatory reduction in circulating endogenous insulin levels in people without T1D. Individuals with T1D experience pathophysiological destruction of beta cells in the pancreas and thus lack the ability to tightly regulate blood glucose levels. Individuals with T1D rely on exogenous insulin, administered via pump or injection to ensure effective transport of glucose into cells. Exogenous insulin is not under strict endogenous feedback control mechanisms and thus peripheral insulin concentrations may rise during exercise due to increased mobilisation from the subcutaneous deposition and a reduction in insulin clearance.

In an individual without diabetes, glucose provision for exercise originates predominantly from the liver as a result of increased levels of glucagon and reduced circulating levels of insulin. However, during exercise in people with T1D, it is not possible to quickly change insulin levels and regulatory hormone responses can either increase or decrease as a consequence of activity [7, 9]. Such hormonal imbalances can be challenging to manage resulting in either hypo, hyper, or euglycaemia [7, 9].

The fundamental physiological principles that underpin glucose regulation during PA provide a foundation for understanding general blood glucose management principles for people with insulin dependent diabetes. However, a high level of individual variability exists in response to exercise, thus planning and managing exercise for people with T1D requires a highly personal approach. In addition to activity specific factors that influence glycaemic response, such as type, intensity, duration of activity (these factors will be discussed in more detail in later sections of this chapter), individual factors also need to be taken into consideration. For example, individual fitness level, initial blood glucose level, c-peptide secretion levels, and residual beta cell function influence glycaemic response during and after exercise or activity [9].

3. Type, duration, and intensity of physical activity and diabetes management

PA is commonly promoted as a method of improving glycaemic control, particularly in the context of the general population, however, there are important metabolic differences in response to PA between children with and without T1D [7]. Type, duration, and intensity of PA will influence metabolic response in T1D and careful planning is required to prevent instances of hyperglycaemia or hypoglycaemia [7, 9]. During aerobic activity, skeletal muscle glucose uptake increases to generate muscular activation. This increase in glucose uptake inhibits gluconeogenesis occurring in the liver and promotes reduction in blood glucose. Subsequently, the risk of hypoglycaemia is increased during aerobic activity. Given the risk of hypoglycaemia, it is pertinent to plan for aerobic activity of long duration or high intensity. Furthermore, exercise and PA is contraindicated for at least 24 hours following a severe hypoglycaemic event (i.e. hypoglycaemia resulting in cognitive impairment).

In addition to hypoglycaemia, hyperglycaemia can present a safety concern for undertaking certain types of PA or exercise. High intensity activity should not be undertaken if blood glucose levels are 14 mmol/L or above. Raised ketones present a safety concern prior to exercise and elevated ketones should be addressed prior to commencing exercise or PA, thus monitoring blood or urinary ketones is advised.

Adjustment to diabetes management regimens is typically required for any form of exercise lasting longer than 30 min [9]. For activity taking place during peak insulin activity time (i.e. soon after a meal), insulin dose reduction may be required. For example, reduction in short acting insulin is typically advised if given within a 2 hour period before exercise and supplementing with a snack if short acting insulin is given more than 2 hours before exercise. Further adjustments to basal insulin and bolus insulin may be required before and for several hours after exercise (e.g. throughout the night) for vigorous aerobic activity that has taken place in the evening. Basal insulin may also need to be reduced before bed depending on activity that has taken place earlier in the day. For insulin pump users, this may mean suspending pump activity temporarily. For those using multiple daily insulin injections, the site of injection may be an important consideration prior to activity. Large muscle groups that will be used during PA or exercise should be avoided as an injection site prior to activity [7, 9].

The requirement to plan for activity duration and intensity can be challenging, particularly for children where pitch-based activities and active play are spontaneous and involve repeated bouts of intense activity interspersed between rest or lower-level activity. Intermittent activity produces lesser reduction in blood glucose due to higher noradrenaline production [10, 11]. Similarly, due to changes in hormonal regulation, short bursts of anaerobic activities can lead to substantial increase in blood glucose. Elevated blood glucose in response to anaerobic activity is transient and can be followed by risk of hypoglycaemia for up to several hours after activity if not managed appropriately [12].

Additionally, the time of day that activity is undertaken can present challenges for children with T1D, nocturnal hypoglycaemia is common after PA during the day [13]. Risk of hypoglycaemia can remain elevated for up to 24 hours following activity due to increased insulin sensitivity associated with exercise.

Knowledge of physiological response to activity can also be a useful adjunct for regulating exercise mediated hypoglycaemia or hyperglycaemia. For example, risk of hypoglycaemia associated with prolonged aerobic activity can be reduced by the inclusion of high intensity bursts of activity (e.g. short sprints or strides) during or after activity. Conversely, hyperglycaemia associated with high intensity or anaerobic activity may be mitigated or reduced by the inclusion of a low-intensity aerobic ‘cool down’ activity. In the following section, commonly deployed strategies for managing and mitigating risk of hypoglycaemia and hyperglycaemia associated with exercise are discussed.

4. Strategies for PA promotion and T1D management

Insulin dose management around PA and exercise is an important component that requires specific education for parents, children, and adolescents. For individuals on multiple daily injection insulin regimens, reducing or missing basal insulin dose is not recommended to offset the increased insulin sensitivity and subsequent risk of hypoglycaemia in the hours following exercise cessation. Conversely, continuous insulin infusions (via pump technology) allow more flexibility for modifying insulin dosing, however, substantial reduction or suspension is not recommended and significant reductions in insulin dosing can lead to hyperglycaemic bouts. Furthermore, the optimal timing of insulin dose modification for exercise remains unclear [13].

Glucose monitoring is the mainstay of diabetes management. Traditionally self-monitoring of blood glucose is undertaken using finger prick assessment but increasingly technology is becoming more commonplace for tracking glucose levels in children and adolescents using real-time continuous glucose monitors (CGM). Information gathered from glucose monitoring allows refinement of future exercise strategies and can inform how different factors and behaviours influence blood glucose levels [13]. There are important differences to consider for self-monitoring of blood glucose levels via finger prick assessment and continuous glucose monitoring. For example, finger prick assessment measures glucose level directly from blood whereas continuous glucose monitoring devices track interstitial glucose levels. A lag can exist between blood and interstitial glucose, that may be pertinent to factor when reviewing glucose levels in response to activity. Consequently, blood glucose levels from continuous glucose monitoring devices may not be representative of decreasing or rapidly falling blood glucose during activity. However, continuous glucose monitors can provide valuable information about blood glucose levels before exercise and blood glucose excursions during and after activity allowing for ongoing refinement of individual-specific, tailored blood glucose management strategies. Unfortunately, some sports and activities may not be conducive to the use of continuous glucose monitoring, for example, contact sports. Different technologies also have different parameters to consider for use during water-based activities (e.g. depth of water, duration of immersion).

Blood glucose levels at the onset of exercise can be used to tailor glycaemic management strategies. 7–10 mmol/l is an acceptable starting range aerobic exercise for up to 60 min duration, however, expert opinion suggests that blood glucose target levels at the start of exercise should be individualised [13, 14]. It is important to note that in addition to starting blood glucose level, the typical rate of change in blood glucose should be taken into consideration to prevent hypoglycaemia. As discussed previously, the time since insulin dosing is another important consideration for activity and exercise management, particularly in relation to carbohydrate supplementation.

Carbohydrate supplementation is also commonly used to offset or reduce the risk of exercise-mediated hypoglycaemia. The risk of hypoglycaemia can often be managed through appropriate replacement of carbohydrate prior to, during, and after physical activity. Factors influencing the amount of carbohydrate intake required to prevent exercise-mediated hypoglycaemia include body mass, circulating insulin levels, and the type, intensity, and duration of exercise [7, 9, 13]. Clinical management with the multidisciplinary care team may include trial and error with both insulin dosing and carbohydrate supplementation to establish the optimal strategies for exercise. This can be particularly challenging for children and adolescents where exercise is not always planned and often spontaneous and intermittent in nature.

5. Psychosocial principles of physical activity and diabetes

Thus far, this chapter has explored the physiological and metabolic factors associated with exercise and T1D. In this section, the psychosocial concomitants of PA participation are discussed. T1D management focus has progressed from solely being concerned with HbA1c optimisation to include holistic markers of both physiological and psychological health. There is a noted psychological burden associated with chronic disease management. The incidence of depression in children with T1D has been reported as three times higher than that of children without diabetes [15]. Exercise and PA may provide a mechanism for supporting psychosocial factors for children and adolescents that contribute to their quality of life and psychological well-being. Thus, it is important to consider the factors that support children and adolescents with T1D to participate in PA and the disease-specific barriers that they experience in leading a physically active life.

During childhood and adolescence, the experience of PA can shape future PA decisions and PA behaviours throughout later life [2, 3, 4, 5, 6, 7]. The transition from childhood to adolescence is typically associated with a notable decrease in PA levels [2, 3, 4, 5, 6, 7]. Therefore, PA experiences early in life can have life-long implications for health outcomes. The Childhood Determinants of Adult Health (CDAH) is a large-scale, longitudinal population-based study that reported the effect of behavioural, attitudinal, sociocultural, and physical factors on PA behaviours in healthy children [15]. For females, perceived competency and for males, physical fitness were found to be significant predictors of persisting with PA into adulthood. Early intervention to promote PA engagement seems imperative in childhood, particularly for children and adolescents with T1D who are at additional risk of low participation and increased sedentarism.

It is well established that in healthy populations, positive experiences in PA and exercise contribute to psychological wellbeing factors (e.g. enjoyment, confidence, and self-efficacy), however, it is important to note that diabetes-specific factors can influence the interaction between PA and psychological wellbeing for young people with T1D. Research has identified multiple barriers to PA engagement in individuals with T1D, fear of hypoglycaemia being reported most frequently. For individuals with T1D, exercise may mask symptoms of hypoglycaemia (e.g. tachycardia, diaphoresis, pallor). Whilst barriers to PA engagement are important to address through appropriate education and support, it is also important to understand the motivators and facilitators to PA engagement for individuals with T1D [16].

In keeping with Bandura’s self-efficacy theory [17] and social cognitive theory [18], active peers and active role models are reported as being supportive of PA engagement for children with T1D. Self-efficacy theory purports that the belief that an individual can successfully perform an activity increases the likelihood of the individual to engage and persist in the activity. Patient compliance with exercise prescriptions is more likely to be successful if exercise self-efficacy is enhanced. Social cognitive theory is a behaviour theory of human motivation and action, that includes cognitive (e.g. self-efficacy) and environmental factors (e.g. social support) that interact with one another to shape human behaviour. Children who experience active families and friends are more likely to sustain an active lifestyle [19]. Self-efficacy and enjoyment are consistently acknowledged as important factors that help children with T1D to remain physically active. Conversely, low self-efficacy, anxiety, and lack of active peers contribute to low PA engagement. Healthcare professionals (HCP) working with children with T1D and their families have an important role to play in supporting and promoting PA. Evidence-based and individualised guidance from HCPs is important for managing the risk of hypoglycaemia and alleviating associated worries [20, 21]. As discussed earlier in this chapter, there are a number of tools and strategies available to aid in the planning and management of PA for children and adolescents (e.g. glucose monitoring, carbohydrate supplementation, insulin adjustment and technology). Each strategy and tool should be planned and managed in conjunction with a HCP team member providing diabetes care to children, adolescents, and their parents.

In addition to support provided in the clinical setting, international guidelines are available to support the promotion of opportunities for children and adolescents to safely participate in a variety sport, exercise, and PA settings. Unfortunately, to the best of our knowledge, there remains a lack of structured education initiatives aimed at transferring these guidelines in to practical application outside the healthcare setting, in schools, and sports clubs etc. Positively, general diabetes education programmes are available, for example, the International Society for Pediatric and Adolescent Diabetes (ISAPD) and International Diabetes Federation provide a structure education initiative for schools (KIDS programme) to promote education about diabetes and diabetes care [22]. Further specialised education initiatives that specifically address sport, physical activity, and exercise promotion for children and adolescents with T1D may help in increasing engagement and participation. The increased visibility of high level and elite sports people with diabetes is an important factor in encouraging and motivating young people with T1D to not only participate but to excel in sport and exercise endeavours.

6. Technology and physical activity

Technology for diabetes management is evolving rapidly. There are multiple modalities available to support day-to-day diabetes care, such as continuous glucose monitors, subcutaneous insulin infusion (insulin pumps), and closed loop technology. In addition to diabetes specific technologies, activity trackers and smartphone applications can provide additional information to support exercise management for individuals with diabetes. Technology allows accessible and transferable information that may be useful for paediatric diabetes management for example, a legal guardian, teacher, coach can access blood glucose information which may increase safety during and after PA or exercise. Some insulin pumps include algorithms that predict low glucose management that may be useful in mitigating or reducing the risk of exercise induced hypoglycaemia both during and after PA. Hybrid closed loop systems are now in use in dedicated paediatric diabetes clinic services and these automatically adjust insulin delivery in response to patterns of both hypoglycaemia and hyperglycaemia. It is important to develop and use individualised insulin patterns for exercise on these next generation insulin pumps [22, 23].

In addition to supporting the management of diabetes during PA and exercise, diabetes technology provides new insights into the impact of PA and exercise on acute and chronic markers of diabetes control. For example, while HbA1c was previously considered standard for monitoring optimal diabetes management, it may mask extremes in glucose variability. CGM provides a measure of ‘time with range’ or ‘time in target’, ‘time above range’ and ‘time below range’ for glucose targets. For accurate interpretation of CGM data, the percentage of time that the sensor is used is an important variable to monitor. Recent research, examining the acute impact of activity on CGM parameters of diabetes control, have provided further advocacy for the utility of moderate to vigorous activity to improve glycaemic control, with children achieving greater percentage time in range without significant time below or above range on days where greater activity levels are achieved [23].

Despite the rapidly evolving diabetes technologies, exercise and PA management remains one of the most significant challenges to automated systems. Technology-based management via continuous insulin infusion does appear to offer more flexibility and can reduce risk of post-exercise hyperglycaemia and delayed or nocturnal hypoglycaemia. However, highly individualised specific management and manual input are still required [13]. Unfortunately, exercise and sport may necessitate the removal/disconnection of pump infusions. Additionally, wearing a pump can present challenges to children and adolescents who may fear stigma or discrimination related to their diabetes.

Non-diabetes specific technology, such as wearable activity trackers that monitor heart rate, activity level, and intensity, can be used in conjunction with blood glucose monitoring, carbohydrate intake, and insulin dosing to better understand and support diabetes management in response to exercise and activity. Additionally, activity tracker technology provides objective, empirical information about parameters of activity (e.g. step count). Such objective information may reduce the challenges associated with ‘self-report’ approaches that are often used to assess and monitor physical activity behaviours in clinical settings. Minimum or ‘target’ step counts are often used as part of public health initiatives and physical activity promotion campaigns. For adults, 10,000 steps are commonly promoted as a daily target for sustaining physical health. For children and adolescents, there is some discrepancy between studies due to age categories, weight categories, and accelerometers/pedometers used, 11,500 steps per day have been identified as a target for both male and female children and adolescents [21, 24]. Activity trackers and smart phone applications can also provide important information about sedentary behaviour patterns, that are often under-reported or not assessed routinely despite the noted independent associations between sedentary time and physical health parameters.

The increasing availability of commercial technology has not only provided valuable clinically relevant information but has also changed the landscape of PA participation and promotion for the general healthy population. For example, smartphone applications and wearable activity tracker devices harness psychological and sociological concepts to support and motivate individuals to engage and persist in PA.

7. Conclusions

PA has potential to improve proactive and prophylactic management for children with T1D. In addition to physical and metabolic outcomes, PA has a positive impact on psychological aspects of living with chronic long-term conditions. PA and exercise management can present a challenge to caregivers, children, and adolescents as well as the multidisciplinary healthcare team, coaches, and teachers. Support and advice based on fundamental physiological principles of type, duration, and timing of PA and subsequent blood glucose response is needed to enable children and adolescents to participate safely in PA and exercise. PA requires careful, individualised planning, and monitoring to ensure appropriate insulin regimen or dietary modifications to reduce the risk of blood glucose excursions following activity. Prior to exercise, individuals with T1D should check their blood glucose levels prior to commencing activity, there should be ready access to glucose monitoring equipment and high glycaemic carbohydrate snacks available to treat hypoglycaemia. Diabetes identification should be worn, and coaches, teachers, and teammates should be made aware of diabetes management requirements. Technology could play an important role in future research and PA promotion practices to aid in the transfer of PA guidelines to real-world changes in PA behaviours for children and adolescents with T1D.