Management of exercise for children and adolescents with type 1 diabetes mellitus

INTRODUCTION — Regular physical activity has important health and social benefits for children and adolescents with type 1 diabetes mellitus (T1DM) and should be encouraged [1,2]. "Exercise" describes a planned form of physical activity. Because exercise and regular physical activity have similar health and fitness benefits for individuals with T1DM, we use the terms interchangeably in this topic review [3].

Exercise also presents several important challenges to diabetes management. It requires special management by patients and clinicians, using protocols based on a sound understanding of the underlying physiology, adapted to the patient's individual characteristics. New analogs of insulin, continuous subcutaneous insulin infusion devices (ie, pumps), continuous glucose monitoring (CGM) devices, and automated insulin delivery systems (sometimes called hybrid closed-loop systems) may improve glucose control around exercise and sport in youth with T1DM. However, regardless of the technology used, the child or adolescent with T1DM requires thoughtful planning and management of glycemic control during and after physical activity.

This topic review will describe the physiology of glucose homeostasis during exercise, then present a clinical approach to management of glycemic control during and after exercise in young patients with T1DM. Similar issues in adults are discussed in a separate topic review. (See "Exercise guidance in adults with diabetes mellitus".)

BENEFITS OF EXERCISE — Regular physical activity is associated with a lower risk of premature all-cause and cardiovascular mortality in patients with T1DM [4]. Children and teens with T1DM should follow the same recommendations for daily exercise, with respect to frequency, duration, and type of physical activity that are recommended for youth without diabetes [2]. (See "Pediatric prevention of adult cardiovascular disease: Promoting a healthy lifestyle and identifying at-risk children", section on 'Physical activity'.)

Other benefits of regular exercise for individuals with T1DM include [5-7]:

●Increased cardiovascular and cardiorespiratory fitness

●Enhanced muscle mass and strength

●Reduced adiposity

●Increased bone mineral density

●Improved insulin sensitivity

●Improved cardiovascular risk profile

●Improved sense of well-being

On average, adolescents with T1DM tend to have reduced exercise capacity and display alterations in muscle and cardiac function compared with nondiabetic youth [8-11]. Unfortunately, children and adolescents with T1DM tend to be less active than their peers, similar to youth with other chronic diseases [12,13]. Among youth with T1DM, lower activity levels are associated with poorer fitness, worse glycemic control, and a greater chance of being overweight or obese [13]. Regular physical activity and exercise training are associated with improved cardiovascular autonomic regulation in adolescents with T1DM [14] and with increased life expectancy in patients living with T1DM [15]. Youth with T1DM who are achieving their various clinical goals (ie, hemoglobin A1c [A1C], lipids, blood pressure, and body mass index) typically have higher aerobic fitness levels, greater skeletal muscle strength and bone health, and greater insulin sensitivity compared with those who are not meeting clinical goals [16-19].

In children and adolescents with T1DM, increasing physical activity lowers A1C levels by approximately 0.3 to 0.5 percentage points (depending on baseline A1C and the amount of exercise), based on cross-sectional studies [20,21] and some interventional studies [22]. Higher amounts of activity on physically active days is associated with increased percentage of time in glucose target range in youth with T1DM [23]. Reducing sedentary time (and, in particular, screen time) appears to be associated with improved metabolic control in this patient population [24]. In one large, cross-sectional investigation of patients ages 3 to 20 years, the individuals with T1DM doing no regular physical activity had the highest A1C levels [25]. Increased computer screen time is also associated with poorer metabolic control in this patient population [26]. Meta-analysis suggests that exercise training lowers daily insulin dose and significantly reduces waist circumference and lipid levels (low-density lipoprotein and triglycerides) [27]. Having better cardiorespiratory fitness is not only associated with better glycemic control in adolescents with T1DM but also with reduced glycemic variability [28], improved health-related quality of life [29], and improved renal function [14]. Adolescents with well-controlled T1DM generally have preserved cardiac function and exercise capacity, but those with poorly controlled T1DM and long disease duration may have elevated baseline and exercise-stimulated heart rates and slightly reduced left ventricular ejection fraction [30]. Exercise training can improve abnormal diastolic function in youth with T1DM [31]. In addition, regular exercise appears to largely help prevent kidney disease in youth with T1DM [32], although a single bout of vigorous exercise temporarily increases microalbuminuria [32,33].

In adults with T1DM, exercise training has not been shown to reduce A1C [5,27,34], although it can reduce total daily insulin needs and improve cardiometabolic parameters such as aerobic capacity and blood lipid levels [27,35].

EXERCISE PHYSIOLOGY

●Aerobic versus anaerobic exercise – Exercise can be described as predominantly "aerobic," "anaerobic," or "mixed" in nature. Aerobic activities are characterized by continuous, rhythmic, and repeated movements of the same large muscle groups for at least 10 minutes at a time. Anaerobic activities are characterized by use of muscular strength to move a weight or to work against a resistant load. In reality, most sporting activities and games are a combination of both aerobic and anaerobic actions. Both aerobic and anaerobic activities are beneficial for health in the growing child with T1DM [36].

In individuals with T1DM, the blood glucose (BG) response to exercise depends on the nature and intensity of the exercise. The responses vary considerably among patients [37], but an individual patient tends to have reasonably consistent responses to a given type and intensity of exercise [38,39].

•Aerobic – Aerobic activities are generally associated with reductions in BG concentrations in T1DM (figure 1). Individuals with higher pre-exercise BG levels tend to have a greater absolute drop in glycemia during prolonged aerobic exercise [37].

•Anaerobic – By contrast, anaerobic and very intensive aerobic activities usually do not reduce BG concentrations and may be associated with elevations in BG under certain circumstances (table 1). As an example, sprinting activity tends to increase BG concentrations (as long as the pre-activity plasma glucose concentration is normal and insulin is at a basal concentration), likely because it is primarily fueled through anaerobic metabolism and is associated with increases in plasma catecholamine and lactate levels [40].

•Mixed – Mixed anaerobic/aerobic activity tends to have moderating effects on glycemia [41]. This includes many forms of team and individual sports and children's playground activities (such as soccer and other field sports, basketball, and baseball) because these activities consist of brief periods of intermittent high-intensity (anaerobic) exercise, intermixed with lower-intensity (aerobic) activity.

●Effects of intensity and duration of exercise – The main fuel sources for prolonged aerobic exercise are lipid and carbohydrate, which are derived from both within and outside of the muscle tissue (ie, muscle lipids, muscle glycogen, blood lipids mobilized from adipose tissue stores, and BG released from liver or from carbohydrate ingestion). The mix of fuel utilization during aerobic exercise (and the amount of disturbance to BG levels) primarily depends on the intensity and duration of the activity as well as the nutrient status of the individual. Initially, the energy used for muscular contraction is derived from stores within the muscle itself, including a very small amount of stored energy in the form of high-energy phosphates (adenosine triphosphate [ATP] and phosphocreatine) and a somewhat larger store of glycogen. With increased exercise duration, there is a gradual shift to fuels from outside of the muscle, including plasma free fatty acids and BG [42]. During prolonged exercise, the main sources of BG are from the breakdown of liver glycogen or ingested carbohydrates [43]. With increasing exercise intensity, there is a progressively greater reliance on carbohydrates as fuel, with a concomitant reduction in the amount of lipids oxidized (figure 2).

This pattern of fuel utilization is largely thought to be similar between children and adults, except that children and adolescents in general have a higher relative capacity for fat utilization, and they may be less able to use muscle glycogen as a fuel [42]. The pattern of fuel utilization in individuals with T1DM is similar to those without diabetes, except that the capacity to oxidize orally ingested carbohydrates may be slightly impaired, and there may be a slightly higher reliance on muscle glycogen and on lipids (figure 2) [44,45].

Because prolonged moderate- to high-intensity exercise primarily relies on carbohydrate as a fuel [46,47], this type of activity often poses the greatest threat for hypoglycemia. In children and adolescents with T1DM, glucose oxidation rates are as high as 1.5 grams of carbohydrate/kg body mass per hour of activity [44], yet only approximately 3 to 4 grams of glucose is stored in the bloodstream of a healthy adolescent [43]. Glycogen stores in liver (40 to 60 grams for a 35- to 50-kg child) and skeletal muscle (150 to 400 grams, depending on the size of the child) represent the main sites of endogenous carbohydrate to fuel exercise. During prolonged exercise, these sources must rapidly restore the circulating supply of glucose to prevent hypoglycemia. Preventive actions to avoid hypoglycemia during and after exercise are discussed below. (See 'Glycemic management during exercise' below.)

●Hormonal regulation and counterregulation – The hormonal response to physical activity consists of a counterregulatory response to the exercise itself and the counterregulatory response to hypoglycemia if it develops.

•Counterregulatory response to exercise – In nondiabetic humans, several mechanisms are entrained during exercise to maintain normal BG concentrations in the face of elevated glucose disposal into working muscles [48]. At the onset of aerobic exercise, the rate of insulin secretion into the portal vein rapidly decreases, which sensitizes the liver to glucagon, thereby allowing for a rapid increase in hepatic glucose production [49]. Meanwhile, there are gradual increases in the blood levels of glucose counterregulatory hormones (glucagon, catecholamines, growth hormone, and cortisol). This change in hormonal profile increases glucose production and maintains circulating glucose concentrations in a normal range during exercise (approximately 70 to 100 mg/dL [4.0 to 5.5 mmol/L]). As a result of the effects of this redundant counterregulatory system, hypoglycemia rarely occurs during exercise in nondiabetic individuals [48,50]. If hypoglycemia does occur, then the counterregulatory hormone response is amplified to help minimize the depth and duration of hypoglycemia [51,52]. During prolonged exercise, the counterregulatory hormones help mobilize various fuels (lipid availability from lipolysis and liver glucose production via glycogenolysis and gluconeogenesis) while limiting peripheral glucose disposal to maintain euglycemia [53].

•Counterregulatory response to hypoglycemia – In nondiabetic humans at rest, progressive decreases in BG concentrations trigger changes in counterregulatory hormones that counteract the fall in glucose [54]:

-BG <80 mg/dL (4.4 mmol/L) – Reduction in insulin secretion

-BG <70 mg/dL (3.9 mmol/L) – Increased secretion of glucagon and epinephrine

-BG <67 mg/dL (3.7 mmol/L) – Secretion of norepinephrine and growth hormone

-BG <65 mg/dL (3.0 mmol/L) – Secretion of cortisol

-BG <55 mg/dL (3.0 mmol/L) – Autonomic symptoms develop (table 2)

-BG <50 mg/dL (2.8 mmol/L) – Cognitive function is impaired

Several factors can impair the counterregulatory response to exercise, including obesity and recent exercise (figure 3). (See 'Pathophysiology' below.)

PATHOPHYSIOLOGY

●Relative hyperinsulinemia – People without diabetes have a rapid coordinated hormonal response to exercise, including a rapid decrease in insulin secretion and more gradual increases in counterregulatory hormones (see 'Exercise physiology' above). In individuals with T1DM, it is impossible to mimic this coordinated hormonal response to exercise because systemic and portal venous concentrations of insulin administered subcutaneously tend to lag behind changes in the physiologic need. As a result, they tend to have systemic and portal venous hyperinsulinemia during exercise:

•Systemic hyperinsulinemia – In people with diabetes, the circulating plasma insulin concentration required to maintain normoglycemia at rest results in relative hyperinsulinemia during aerobic exercise. This is especially evident for exercise in the postprandial state, when plasma insulin levels may be two- to threefold higher in the systemic circulation in the adolescent with T1DM compared with nondiabetic youth during exercise in the postprandial state [44]. These elevated insulin concentrations promote peripheral glucose disposal and reduce hepatic glucose production, causing a rapid reduction in blood glucose (BG) concentrations at the onset of exercise.

•Portal hyperinsulinemia – In people with diabetes, there is little variation in portal venous insulin concentrations because the insulin is administered subcutaneously. In particular, changes in insulin concentrations in the portal circulation occur only gradually. At the onset of exercise, these individuals do not experience the rapid decrease in plasma insulin concentration in the portal vein that would normally sensitize the liver to glucagon and increase hepatic glucose production [43,49].

Because of systemic and portal venous hyperinsulinemia, children with T1DM are at risk for hypoglycemia during exercise. A child has only approximately 3 to 4 grams of glucose in the circulation, and exercise increases glucose utilization rates five- to sixfold above the resting rate [49]. As a result, hypoglycemia can ensue within minutes if circulating insulin levels are not reduced in anticipation of the activity or if exogenous carbohydrates are not consumed at the start of exercise [55].

In addition, exercise appears to accelerate absorption of subcutaneous insulin for patients receiving injections as well as for those on continuous subcutaneous insulin infusion therapy [56,57].

●Counterregulatory failure – In addition to the relative hyperinsulinemia described above, young people with T1DM may have other endocrine disturbances that increase their risk for exercise-associated hypoglycemia. Although their counterregulatory response to exercise is generally normal, they are unable to lower insulin secretion at the onset of exercise [58]. Nonetheless, the glucagon response to hypoglycemia is impaired, especially in those who have had repeated episodes of hypoglycemia or after antecedent exercise [59]. Thus, serial episodes of exercise and hypoglycemia further blunt the counterregulatory hormone response, contributing to a vicious cycle that predisposes the individual to further deterioration in glucose control (figure 3).

CLINICAL CONSEQUENCES — Although regular physical activity may have important benefits on long-term glycemic control, it is also associated with short-term risks for hypoglycemia and hyperglycemia, both during exercise and in the hours and night after the exercise session. Newer automated insulin delivery systems (sometimes called hybrid closed-loop systems) may offer additional benefits for some active patients since these devices appear to effectively mitigate both hyper- and hypoglycemia during and after exercise [60].

Hypoglycemia — Increased physical activity increases hypoglycemia risk by approximately 30 to 50 percent both during and after exercise (for up to approximately 12 hours) in children and adolescents with T1DM [37,55,61].

Exercise induces hypoglycemia because muscle contraction increases glucose uptake via insulin-independent mechanisms [62] and also because it enhances insulin sensitivity in a temporal pattern that depends on the time of day as well as the type and duration of exercise performed. When exercise is performed early in the day, the risk of immediate hypoglycemia may be less than when exercise is performed later in the day [63,64], but heightened insulin sensitivity is sustained for at least 11 hours after the morning exercise is completed [64-66]. In contrast, exercise performed late in the day is associated with a biphasic change in insulin sensitivity, such that heightened insulin sensitivity occurs during the exercise and again 7 to 11 hours later during the overnight hours [67]. This increases the risk for hypoglycemia late in recovery, usually when the child or adolescent is sleeping. As a result, afternoon exercise tends to increase hypoglycemia risk compared with morning exercise [63].

Alcohol should be avoided before and during exercise [1]. Alcohol promotes hypoglycemia, reduces hypoglycemia symptom awareness, and may impair performance [68]. If alcohol is consumed after exercise, additional measures should be taken to avoid hypoglycemia (eg, additional insulin reductions or increased carbohydrate intake) [68].

Immediate hypoglycemia — Even moderate exercise causes hypoglycemia in a substantial number of children with T1DM. In one study of 50 children and adolescents with T1DM performing mild exercise (four 15-minute bouts of walking on a treadmill, each separated by five-minute rest periods), 30 percent developed hypoglycemia during the activity [55]. Among those with a pre-exercise blood glucose (BG) <120 mg/dL (6.7 mmol/L), 86 percent became hypoglycemic. Risk factors that predispose the patient to hypoglycemia during exercise include the duration and intensity of the activity, younger age, high circulating levels of insulin prior to exercise, antecedent exercise, antecedent hypoglycemia, obesity, novelty of the activity, or deconditioning (figure 3) [69].

The risk for hypoglycemia can be mitigated by consuming additional carbohydrates just before and/or during exercise [70] and by monitoring BG levels frequently with fingerstick or by continuous glucose monitoring (CGM) [71], as discussed in more detail below. (See 'Glycemic management during exercise' below.)

Delayed (nocturnal) hypoglycemia — The increase in insulin sensitivity after exercise increases the risk for post-exercise hypoglycemia; the change in insulin sensitivity can last 12 to 24 hours, depending on the amount and intensity of the activity [64]. Nocturnal hypoglycemia is a significant problem for children and adolescents with T1DM and a cause of concern for their parents and caregivers [1,2,72]. Contributing factors include delayed glucose-lowering effects of exercise [65,67,73], sleep-induced defects in counterregulatory hormone responses to hypoglycemia [74-76], and missed bedtime snacks. The risk in children appears to be greater than for adults with T1DM, perhaps because children tend to be much more physically active than adults, especially in the afternoon.

Nocturnal hypoglycemia is most likely to occur during the early morning hours (around 2 to 3 AM), although it can occur at any time [73,74,77-81]. This pattern can be triggered, in particular, by exercise during the afternoon, which increases insulin sensitivity overnight [67] and blunts glucose counterregulatory hormones [74] (see 'Pathophysiology' above). As an example, in a study of 50 adolescents performing just 60 minutes of mild exercise in the afternoon, 48 percent developed nocturnal hypoglycemia (with a nadir at approximately 2 AM) or required carbohydrate treatment to prevent nocturnal hypoglycemia [61]. In another study, 30 minutes of moderate- to vigorous-intensity exercise performed in the late afternoon was associated with a 30 percent increased risk for hypoglycemia during the night and following day [82]. These findings highlight the importance of adjusting insulin doses and carbohydrate intake to avoid post-exercise hypoglycemia.

Strategies for avoiding delayed hypoglycemia are discussed below. (See 'Post-exercise recovery period and protein intake' below and 'Blood glucose monitoring' below.)

Hyperglycemia — Although exercise typically causes a decrease in BG concentration in individuals with T1DM, it can also cause an increase in BG if the exercise is of a very high intensity for a short duration, such as sprinting or resistance exercise (figure 1) [83,84]. High-intensity interval exercise in a fasted state tends to cause a rise in glucose concentration [38] that may require insulin administration [85].

●Risk factors – Hyperglycemia during and after exercise can be caused by any of the following factors:

•High-intensity exercise – High-intensity anaerobic exercise (sometimes defined as >80 percent VO₂max [maximal oxygen uptake]) can cause hyperglycemia, perhaps because it increases catecholamine and lactate levels, which are associated with increased hepatic glucose production and reduced skeletal muscle glucose uptake [86]. Examples include sprinting or speed skating. Management of glycemia is further complicated by participation in team sports that require bursts of intense activity punctuated by rests in play (eg, baseball, soccer, basketball, or hockey), in which case the periods of inactivity also contribute to the risk for hyperglycemia [41,87]. Short bouts of intense resistance-type exercise (eg, weight lifting) also increase BG levels, which can be corrected with judicious insulin administration [88].

•Psychological stress of competition – Psychological stress also may induce cortisol, catecholamines, and interleukin-6 release and promote insulin resistance in youth [89]. Even the stress of video game playing can promote increases in glucose counterregulatory hormones and hyperglycemia in youth with T1DM [90,91]. The clinical relevance of this phenomenon is that patients may develop hyperglycemia just before competition even if they are able to maintain good glycemic control in the preceding days. This means that some individuals may need to compensate for psychological stress during competition by taking slightly more insulin and/or reducing carbohydrate intake, as compared with their standard glycemia management for exercise.

•Environmental factors – Some individuals find that training or competing in warm and humid environments also elevates BG concentrations, likely because of excessive increases in circulating plasma catecholamines, glucagon, cortisol, and growth hormone [92]. On the other hand, exercise in warm environments also increases rates of subcutaneous insulin absorption as a result of heat-induced vasodilation, which accelerates the insulin's hypoglycemic effects [93]. As a result, the effect of a warm environment on BG may not be consistent or predictable.

•Errors in insulin and carbohydrate management – Hyperglycemia during or after sport can also be caused by excessive consumption of carbohydrates, insufficient insulin administration, excessive reductions in basal or bolus insulin delivery, prolonged insulin pump removal (>2 hours), a blocked infusion set in patients on an insulin pump, or from missed insulin injections [94-96].

Exercise is more likely to induce hyperglycemia in individuals in poor metabolic control [97]. Even individuals in good metabolic control may have increases in BG concentrations during and after high-intensity exercise [98], likely because of large increases in catecholamine levels, which promote increased glucose production and attenuated rates of glucose disposal [40,86].

●Management – Hyperglycemia that occurs during or soon after intensive exercise must be managed cautiously; a full insulin correction bolus in an attempt to correct the hyperglycemia at the start of exercise may lead to hypoglycemia during or after the activity [67,94]. If the BG levels rise above 270 mg/dL (15 mmol/L) during or soon after exercise, a partial insulin bolus correction may be warranted, typically administered after the exercise is completed [85,99]. (See 'Initial approach based on blood glucose and ketones' below.)

Hyperglycemia and excessive ketosis during exercise are particularly undesirable as they can cause dehydration and may decrease blood pH, both of which impair exercise performance and place the child at risk for metabolic deterioration into ketoacidosis [97]. People who use an insulin pump (continuous subcutaneous insulin infusion) appear to have less post-exercise hyperglycemia compared with those on multiple daily injection treatment [100], particularly if the device is an automated insulin delivery system [64].

CONTRAINDICATIONS TO EXERCISE — The child or adolescent with T1DM should be encouraged to engage in a wide variety of physical activities with minimal restrictions but with careful management to avoid the risks for hypoglycemia and hyperglycemia that are outlined above. The following issues should be specifically addressed prior to exercise:

Severe hypoglycemia, hyperglycemia, or ketosis — The blood and/or sensor (interstitial) glucose concentration should be checked prior to beginning exercise. The optimal target range for glucose prior to exercise is between 90 and 270 mg/dL (5.0 to 15 mmol/L). Those with glucose in this range usually can proceed safely with exercise, with adjustments of carbohydrate intake and insulin, as outlined below (see 'Initial approach based on blood glucose and ketones' below). Patients with hyperglycemia (glucose ≥270 mg/dL [13.9 mmol/L]) should check for ketones.

Absolute or relative contraindications to exercise are [101,102]:

●Recent episode of severe hypoglycemia – Exercise is contraindicated if there has been an episode of severe hypoglycemia within the previous 24 hours. Severe hypoglycemia is defined as glucose <54 mg/dL (3 mmol/L) or a hypoglycemic event with cognitive impairment requiring external assistance. Antecedent severe hypoglycemia impairs the hormonal counterregulatory response during exercise, thus increasing the risk for recurrent hypoglycemia.

Patients with nonsevere hypoglycemia (glucose >54 to 70 mg/dL [3.0 to 3.9 mmol/L]) should be treated prior to beginning exercise, as described below, and carefully monitor their glucose levels during the activity. (See 'Glycemic management during exercise' below.)

●Severe hyperglycemia with ketosis – Patients with hyperglycemia (glucose ≥270 mg/dL [15 mmol/L]) should check for ketones (ideally with blood beta-hydroxybutyrate [BOHB] testing) prior to initiating exercise. If ketones are elevated (ie, BOHB ≥1.5 mmol/L) or if hyperglycemia is severe (glucose ≥350 mg/dL [19.4 mmol/L]), exercise is contraindicated. Patients with lesser degrees of ketosis may proceed with moderate exercise after correction of blood glucose (BG) with supplemental insulin and with close monitoring [102], as outlined below. (See 'Initial approach based on blood glucose and ketones' below.)

If a sensor glucose (SG) measurement is borderline for either hypo- or hyperglycemia, a fingerstick BG should be measured since sensor accuracy deteriorates with exercise [101,102].

Injuries — Exercising with an injury is not recommended. This is because an injury may precipitate hyperglycemia in patients with T1DM because it tends to increase catecholamine and cortisol responses [103]. Hyperglycemia also may impair the injury recovery process [103]. Conversely, hypoglycemia may increase the risk for both acute injury and sustained organ damage [104].

GLYCEMIC MANAGEMENT DURING EXERCISE — Maintaining adequate glucose concentrations during exercise is critical for the provision of carbohydrate to the working muscle and for normal brain function. Carbohydrates are the predominant substrate utilized during high-intensity exercise. The amount of glucose in the circulation is minimal and must be continuously replenished during exercise, primarily from the much larger stores of endogenous carbohydrates in the liver and skeletal muscle.

Strategies to help maintain targeted glucose levels during exercise include [1]:

●Reduction in exogenous insulin dose – Reducing the insulin dose given prior to exercise reduces the risk for hypoglycemia and the need for exogenous carbohydrates. (See 'Insulin management and adjustments' below.)

●Consumption of extra carbohydrates – Children or adolescents with T1DM generally need to consume extra carbohydrates prior to, during, and after exercise that lasts more than 60 minutes. This strategy also is most practical for the spontaneously active child, for whom exercise is not always predictable, and when timely insulin reduction is not possible. The quantity and timing of the extra doses of carbohydrates depend on many factors, including the intensity and duration of the exercise. (See 'Nutritional management' below.)

Initial approach based on blood glucose and ketones — The blood glucose (BG) concentration should always be checked prior to exercise.

●If sensor glucose (SG) is measured (ie, for people using a continuous or intermittent glucose monitoring device) and the result is in the hypoglycemic range, the results should be confirmed by fingerstick (measuring BG) because changes in SG lag behind BG. (See 'Continuous glucose monitoring' below.)

●If BG or SG is significantly elevated (ie, ≥270 mg/dL [≥15 mmol/L]) and the elevation is not explained by the recent consumption of a meal or snack, the blood or urine should also be checked for ketones.

To assess for ketosis, the optimal approach is to use a point-of-care device to measure the blood beta-hydroxybutyrate (BOHB) concentration. Such a device may not be available to all patients but is valuable and strongly encouraged for those who engage in moderate or intense exercise. A BOHB testing device is also recommended for patients with a history of recurrent ketosis, for those who are trying to lose weight or are embarking on a low-carbohydrate diet, or for those taking a sodium glucose cotransporter inhibitor (SGLT1/2i) (see "Management of blood glucose in adults with type 1 diabetes mellitus", section on 'Adjunctive therapy not recommended'). If BOHB testing is not available, tests for urine ketones (nitroprusside-containing strips that qualitatively measure acetoacetate and acetone) can be used as an alternative. However, urine test strips are an inaccurate measure of ketosis because changes in urine ketones lag behind changes in blood ketones and are also affected by factors such as urine concentration (hydration status) and timing of voiding. (See "Diabetic ketoacidosis in children: Clinical features and diagnosis", section on 'Ketosis'.)

We suggest the following initial management:

●Glucose below target range – If the glucose concentration is <90 mg/dL (<5 mmol/L), treat by ingesting 10 to 20 grams of fast-acting carbohydrate, depending on the size of the child. Delay exercise until the glucose concentration is >90 mg/dL (5 mmol/L).

●Glucose in target range for beginning exercise (90 to 270 mg/dL [5 to 15 mmol/L]):

•Glucose 90 to 125 mg/dL (5 to 6.9 mmol/L) – The child should consume 10 to 20 grams supplemental carbohydrates before starting aerobic exercise.

•Glucose 126 to 180 mg/dL (7.0 to 10.0 mmol/L) – Proceed with aerobic or anaerobic exercise, but the child should consume supplemental carbohydrates soon after beginning exercise for activities that will last more than 30 minutes.

•Glucose 180 to 270 mg/dL (10.1 to 15.0 mmol/L) – Proceed with mild- or moderate-intensity aerobic or anaerobic exercise.

This general plan should be modified based on the patient's history of glycemic response to exercise under similar conditions, fitness level, recent boluses of insulin ("insulin on board"), and trend on continuous glucose monitoring (CGM) or intermittently scanned CGM (isCGM), if used. Consensus guidelines for the use of CGM or isCGM for exercise for children and adolescents are summarized in the table (table 3) [102]. As an example, if the glucose trend is stable or increasing, the carbohydrate dose should be reduced or eliminated. Detailed guidance for pediatric and adult patients using a CGM or isCGM during exercise is provided in a consensus document [102].

During exercise, the child should consume approximately 0.5 to 1.0 g/kg body weight per hour, depending on the energy expenditure and the amount of circulating insulin at the time of exercise (less carbohydrate consumption will be needed if the insulin dose was reduced in anticipation of the exercise). This body weight-based recommendation roughly translates to 20 to 40 grams of extra carbohydrate per hour, without bolus insulin, for a 90-pound adolescent exercising for one hour. (See 'Carbohydrate intake before and during exercise' below.)

●Glucose above target range – If the glucose concentration is ≥270 mg/dL (15 mmol/L), measure ketones, ideally by measuring BOHB using a point-of-care device. Management depends on the degree of hyperglycemia and ketonemia.

•For individuals with mild ketosis (eg, BOHB 0.6 to 1.0 mmol/L; or urine ketones +, trace, or small) and glucose <350 mg/dL (19.4 mmol/L), it is safe to begin moderate exercise, but vigorous exercise should be avoided because it may worsen the hyperketonemia [97]. A partial insulin bolus correction may be warranted (eg, use 50 percent of the usual correction bolus), followed by frequent glucose monitoring.

•For those with moderate ketosis (eg, BOHB 1.0 to 1.4 mmol/L; or urine ketones ++, moderate, or large), exercise should be deferred until glucose and hyperketonemia have been corrected with extra insulin.

The rapid production of ketone bodies during intensive exercise may precipitate ketoacidosis, manifested by abdominal pain and vomiting. If these symptoms occur, exercise should be terminated and the individual should be promptly evaluated and treated. (See "Diabetic ketoacidosis in children: Clinical features and diagnosis".)

•Exercise is contraindicated for people with more severe ketosis (eg, BOHB >1.5 mmol/L or urine ketones ++/+++, moderate, or large) or for those with severe hyperglycemia (glucose ≥350 mg/dL [19.4 mmol/L]) regardless of severity of ketosis. These patients should follow sick-day rules for management of hyperglycemia and ketosis. (See 'Contraindications to exercise' above and "Management of type 1 diabetes mellitus in children during illness, procedures, school, or travel", section on 'Sick-day management'.)

Regardless of the initial glucose concentration, it should be monitored regularly during exercise (every 30 to 45 minutes, or use CGM) and the insulin dose and carbohydrate intake should be adjusted accordingly. Ketones should also be checked if necessary (eg, if glucose rises above 250 mg/dL or symptoms of nausea or vomiting develop). (See 'Blood glucose monitoring' below.)

Nutritional management — Carefully regulated consumption of carbohydrates before, during, and after exercise is an important consideration for exercise management. The timing and dose of carbohydrate depends on the type, duration, and intensity of exercise; concurrent adjustments of the insulin dose; and the unique responses of the individual patient. The dose should be adjusted as needed depending on serial monitoring of BG (or CGM). Individuals with T1DM who follow a low-carbohydrate diet may be at risk for compromised muscle and/or liver glycogen reserves [105]; if severe hypoglycemia develops, they may be resistant to exogenous glucagon rescue [106].

Carbohydrate intake before and during exercise — If no insulin adjustments are made in anticipation of exercise, then additional carbohydrates are usually needed to prevent hypoglycemia. The carbohydrate requirements vary widely, ranging from 15 to 40 grams of carbohydrates (or 0.3 to 1 grams of carbohydrate/kg body mass for young children) per 30 minutes of activity. In most cases, the consumption of more than 60 grams per hour of exercise is not recommended, because this is approximately the upper limit for carbohydrate absorption [107].

For most adolescents, a reasonable starting dose of carbohydrates is 0.5 grams/kg/hour of exercise [108]. At least a portion of this should be consumed approximately 15 to 30 minutes before the activity if the glucose concentration is in the normal range or just slightly elevated [109-111]. In two small studies of youth with T1DM, 0.5 grams of carbohydrate/kg body mass per hour of exercise (approximately 0.25 gram/pound body mass per hour of exercise) helped to maintain glucose concentrations during aerobic exercise [70,108]. The wide range in pre-exercise carbohydrate requirement reflects the size of the child and the wide variation in exercise timing with respect to mealtime bolus insulin injection. For example, if adolescents are exercising at a time of low insulin action (eg, more than three hours after a mealtime bolus of rapid-acting insulin), then less pre-exercise carbohydrate consumption may be necessary compared with individuals performing exercise during peak insulin action (eg, within 60 to 120 minutes after a bolus of rapid-acting insulin) [112].

The amount of carbohydrates required to maintain euglycemia depends on the intensity of exercise and the state of insulinemia prior to exercise. If insulin dose reductions have been made in anticipation of increased activity, then the amount of extra carbohydrates required to maintain euglycemia may be as little as a few grams per hour [71]. As an example, if an insulin pump is used and the basal rate is reduced 90 minutes before beginning mild exercise, typically, no carbohydrate is needed [113]. On the other hand, if the activity is intense and performed during peak insulin action (usually approximately one to two hours after rapid-acting prandial insulin is administered or two to three hours after regular insulin is administered), then as much as 1.0 to 1.5 grams of carbohydrate/kg body weight per hour of activity may be needed [1,36].

One approach to calculating the total amount of carbohydrates needed before and during exercise is to use a table of carbohydrate equivalents, which estimates the rate of carbohydrate utilization during various forms of sport activity, assuming that the insulin dose was not reduced in anticipation of the activity. The carbohydrate requirement calculated using this approach is sometimes termed "extra carbohydrates for exercise" or "ex-carbs" (table 4). These tables are only guidelines, and individual glucose responses to exercise and to carbohydrates vary considerably and should be considered [114].

If used for hypoglycemia treatment or prevention based on SG trend arrows, the carbohydrate should be in the form of rapid-acting, high-glycemic index snacks or carbohydrate-electrolyte drinks and should be consumed without any insulin administration and in divided portions during the activity [36]. For example, a 40-kg child who is swimming for one-half an hour should consume a total of 27 grams of extra carbohydrate (ie, 9 grams approximately 15 minutes before and at 0 and 15 minutes during the activity) (table 4). These rapidly absorbed simple carbohydrates (eg, dextrose) will appear in the blood stream within minutes of consumption. By contrast, a low-glycemic index meal or snack (eg, maltodextrin) is less useful to prevent hypoglycemia during exercise but will help to prevent delayed hypoglycemia for up to several hours after the exercise because of its slow breakdown in the gastrointestinal system.

Post-exercise recovery period and protein intake — During the recovery period after moderate or vigorous exercise, it is generally helpful to consume a snack consisting of mixed protein and carbohydrates [1]. Examples of suitable recovery snacks include dairy-based fruit smoothies, low-fat milkshakes, yogurt drinks, and fruit mixed with yogurt, with an estimated carbohydrate:protein ratio of 2:1. The snack should generally be taken with insulin to avoid post-exercise hyperglycemia. The mixed composition of the snack helps to avoid post-exercise, late-onset hypoglycemia and also supports protein synthesis. Children and adolescents have higher protein requirements relative to adults to support maturational growth. Protein requirements in young athletes are higher than in nonathletes, approaching approximately 1.7 grams protein/kg body weight daily [115].

Insulin management and adjustments — Alterations to insulin delivery may be the best way to attempt to mimic the normal physiologic response to exercise (ie, less insulin for steady-state aerobic exercise; more insulin for brief, high-intensity exercise). However, even the most sophisticated insulin treatment regimen (ie, a hybrid closed-loop automated insulin delivery system) cannot fully mimic the minute-by-minute changes in insulin needs caused by most types of exercise. (See 'Pathophysiology' above.)

When moderate- to vigorous-intensity aerobic exercise is planned (continuous or intermittent exercise lasting more than 60 minutes), we recommend adjustment of the pre-exercise insulin regimen, in addition to the extra carbohydrate intake described above [1]. Adjustment of insulin dose prior to exercise typically is not required for light-intensity activities lasting <60 minutes or for more intense activities lasting <20 minutes, although additional carbohydrates may be needed. (See 'Nutritional management' above.)

Multiple daily injections — If prolonged exercise is to be performed within three hours after a meal (postprandial exercise), then reductions in premeal, rapid-acting insulin (eg, insulin lispro, insulin aspart, faster-acting insulin aspart [Fiasp], or insulin glulisine) or short-acting insulin (eg, regular insulin) should be considered according to the following table (table 5) [116].

On days of increased physical activity (such as attendance at a camp with extensive physical activity or participation in a tournament), then a 10 to 20 percent reduction in intermediate-acting (NPH [neutral protamine hagedorn]) insulin levels should also be considered [117,118]. Very long-acting insulins (eg, U-300 glargine insulin, insulin degludec [U-100 or U-200]) do not permit short-duration adjustments for exercise. However, one can try to reduce insulin detemir and insulin glargine (U-100) by 10 to 20 percent before or after the exercise to help reduce hypoglycemia risk [119]. For those on the very long-acting insulins, additional carbohydrates for exercise and adjustments to mealtime insulin are recommended. In certain circumstances (camps, tournaments, etc), planned reductions in very long-acting insulins may be warranted. (See 'Camps' below.)

Insulin pump — Use of an insulin pump (continuous subcutaneous insulin infusion) is a valuable option for patients with T1DM who are physically active because this approach facilitates rapid adjustments in insulin infusion to match the glycemic changes induced by exercise. One or more of the following approaches may be used, depending on the timing of exercise and the patient's previous glycemic patterns in response to exercise [1]:

●Reduction of basal insulin infusion prior to exercise – When moderate to vigorous physical activity is planned, the basal rate of insulin infusion should be reduced 60 to 90 minutes before the onset of exercise to reduce the risk for hypoglycemia during the activity and the requirement for extra carbohydrates during exercise [120,121]. The amount of basal rate reduction ranges from 20 to 100 percent depending on the intensity and duration planned for the activity [120]. Patients can experiment with a 50 to 80 percent basal rate reduction initially and monitor BG frequently (every 20 minutes, or CGM) to fine-tune this adjustment.

●Reduction of pre-meal insulin bolus for postprandial exercise – As an alternative, exercise performed in the postprandial state (within three hours after a meal) can be managed by reducing the pre-meal bolus of rapid-acting insulin (the same dose reduction used by patients' multiple daily injection regimen (table 5)) [120]. In this case, the basal insulin infusion rate is not changed, unless experience has indicated a need to reduce both to prevent hypoglycemia in the individual patient.

●Suspension of the insulin infusion – In addition to these measures, it is often helpful to temporarily turn the insulin pump off before the start of exercise [80]. However, prolonged suspension of the infusion (>90 minutes) should be avoided because the resulting hypoinsulinemia can contribute to post-exercise hyperglycemia [80,122]. If the pump is disconnected for play or sport, the infusion set can be left intact so that the patient can quickly reconnect to administer (bolus) small amounts of rapid-acting insulin during breaks in play, if necessary. Suspension of the insulin infusion should be used in conjunction with extra carbohydrate intake during exercise, as described above. When used in isolation, it offers little protection against hypoglycemia [123], perhaps because the reduction in circulating insulin levels do not occur fast enough and also because the exercise may enhance insulin absorption from the subcutaneous tissue.

Turning off the pump for short periods of time (<60 minutes) does not appear to promote hyperglycemia [124]. For children and teens who prefer to exercise without the pump in place, but who may require some circulating insulin, the youth can give an insulin bolus before disconnecting the pump; the dose should be approximately equivalent to one-half the basal rate that would have been delivered during the time when the pump would be disconnected. For example, if the basal rate is 1.0 unit/hour and the pump will be off for 90 minutes, the youth can bolus 0.75 units prior to disconnecting the pump. BG levels (or CGM) should be monitored to determine if more insulin or carbohydrates are needed.

●Reduction of basal insulin infusion at bedtime – Individuals using an insulin pump can also program temporary basal rate reductions (20 percent reduction) beginning at bedtime and lasting for six hours to help protect against nocturnal hypoglycemia [72,79].

Hybrid closed-loop insulin delivery system — Hybrid closed-loop insulin delivery systems (also known as an artificial pancreas) are increasingly used in the management of T1DM. Because these devices automatically increase, decrease, and suspend basal insulin delivery, they have the potential to improve glucose time in target range, particularly after exercise [125]. However, the approach differs from standard management in several ways:

●Target glucose – Set a higher SG target before exercising (sometimes called "exercise mode"), ideally starting 90 to 120 minutes before the exercise begins [126,127]. Some closed-loop systems have preprogramed ranges for exercise, such as 140 to 160 mg/dL (eg, Tandem t:slim with Control-IQ), while others have a fixed target for exercise (eg, Medtronic 670G uses 120 mg/dL as the target). With any hybrid closed-loop system, emerging evidence supports setting the SG target for exercise approximately 60 minutes before the activity begins and turning the temporary target off when the exercise is completed [60].

If post-exercise hypoglycemia is a concern (eg, after very prolonged and unusual activity or in a patient with a history of post-exercise hypoglycemia), continue to use exercise mode and postpone reverting to standard mode after exercise for up to six hours in recovery. The higher target can also be used overnight if nocturnal hypoglycemia is a concern.

●Timing of exercise – When possible, the timing of exercise should be three or more hours after a meal to allow the effect of prandial insulin to dissipate by the exercise start time. If exercise is planned within one to two hours of a meal, reduce the premeal bolus by approximately 25 to 50 percent [60]. These strategies are useful because the device is less effective for managing glycemia during the time of peak postprandial insulin action. Larger reductions of the prandial insulin dose before exercise are not recommended, since this often results in pre-exercise hyperglycemia, which will increase the automated insulin delivery and/or promote an automated bolus correction in some systems, thus increasing circulating insulin levels during the activity.

●Disconnecting the device – The patient may choose to disconnect the device during exercise, similar to the strategy sometimes used for a standard insulin pump (see 'Insulin pump' above). However, if this is done, it is important to also suspend the insulin infusion so that the algorithm accurately tracks the amount of insulin delivered [60].

●Carbohydrate intake – Unless the patient is hypoglycemic, they should not consume "free" carbohydrate snacks (ie, no bolus insulin given) during the hour before exercising, since this will cause an automated increase in insulin delivery just before exercise. However, simple carbohydrates can be consumed just before the start of exercise and/or during the exercise, after the device has been set to the higher glucose target (ie, exercise "mode").

Some individuals may need to ingest carbohydrates during exercise to avoid hypoglycemia and optimize performance. If so, they usually should not record that carbohydrate intake in the device, since this may result in excessive insulin infusion in some systems.

(See "Continuous subcutaneous insulin infusion (insulin pump)", section on 'Insulin only, partially automated system'.)

Blood glucose monitoring — The BG response to exercise is variable among youth with T1DM [37]; however, the individual patterns of response are somewhat reproducible for a given individual and for a specific activity if several variables are held constant (insulin levels, exercise type, and timing) [39]. BG should be monitored frequently before, during, and after exercise because glucose levels can change rapidly, and good glycemic control is important to maintain performance and safety. Ideally, CGM should be used if it is deemed acceptable and affordable for the family [101,102].

Episodic monitoring — At least two measurements of BG should be taken in the hour prior to exercise so that the direction of change in BG concentrations can be assessed and so that preemptive interventions can occur before the start of the activity [120]. We also advise measuring BG every 30 minutes during the exercise to help anticipate and prevent hypo- or hyperglycemia [120]. Increased frequency of monitoring during the recovery period after exercise is also recommended to avoid post-exercise, late-onset hypoglycemia [79].

Continuous glucose monitoring — CGM is performed using a subcutaneous sensor that continuously measures glucose levels in interstitial fluid. Guidelines encourage the use of CGM during exercise [1,102]. This technology offers a considerable advantage for patients who are physically active because of the need for frequent BG monitoring and insulin adjustment during and after exercise and because it is impossible to precisely predict the glycemic changes induced by exercise [81,99]. Although CGM is reasonably accurate during both aerobic and anaerobic exercise [128], the SG lags significantly behind BG level [129,130]. Therefore, people with current or recent hypoglycemia should confirm SG results with a fingerstick (BG) measurement [1].

Directional rates of change on CGM systems and sensor-augmented pumps can inform users if glucose concentrations are outside of the target range, and alerts and alarms are useful to alert the patient to hypo- or hyperglycemia [131]. These functions can help the patient to make informed decisions about insulin dosing and the need for extra carbohydrate ingestion during and after exercise [102,131]. CGM can also be useful to detect nocturnal hypoglycemia that can be a late effect of exercise and to alert the patient by sounding an alarm during sleep [81]. First-generation, automated insulin delivery systems (also referred to as the artificial pancreas) are now available for use in clinical as well as research settings [132-134]. Exercise management, however, remains a challenge even with use of these systems [135]. (See "Insulin therapy for children and adolescents with type 1 diabetes mellitus", section on 'Automated insulin delivery (hybrid closed-loop insulin pumps)' and "Management of blood glucose in adults with type 1 diabetes mellitus", section on 'Continuous subcutaneous insulin infusion (insulin pump)'.)

Details about using CGM to guide insulin and carbohydrate dosing before, during, and after exercise are provided in a consensus guideline for adults and adolescents with T1DM [101,102]. This incorporates directional rates of change in BG, the patient's fitness level (frequency of exercise), and blood ketones (table 3).

Of note, this guidance does not apply to patients using hybrid closed-loop systems; management of exercise for such patients is outlined in a different consensus document [60].

SPECIAL CONSIDERATIONS

Schools — Participation in vigorous exercise during physical education classes and other active parts of the school day (eg, recess, lunch, after-school activities) can be associated with disturbances in blood glucose (BG) concentrations. Students with T1DM should fully participate in physical education classes and team sports, provided that there is good communication and collaboration between the student, his or her health care provider and parents, the school nurse, and the physical education instructor or team coach and good adherence to a well-designed regimen for glycemic control during and after exercise. A diabetes care plan should be in place for the child or adolescent and should include specific instructions for teachers, instructors, and coaches [136].

For physical education classes, the steps to prevent exercise-induced hypoglycemia are similar to those outlined above. They include measurement of BG or sensor glucose (SG) prior to exercise. Depending on the results of this measurement, management may include reductions in the insulin dose prior to exercise and/or ingestion of additional carbohydrates (eg, 0.3 to 1 gram of carbohydrate/kg body weight per hour of exercise). If glucose is significantly elevated (≥250 mg/dL [≥13.9 mmol/L]), ketones should be measured in blood or urine. (See 'Glycemic management during exercise' above.)

Actions for the physical education instructor or coach include:

●General approach:

•Encourage exercise and participation in physical activities/sports for all students with diabetes.

•Treat the student with diabetes the same as other students, except in meeting his or her medical needs (remember to respect the student's right to privacy and confidentiality).

•Be prepared to recognize the signs and symptoms of hypoglycemia and hyperglycemia (table 2) and to respond appropriately to high or low glucose concentrations.

•Communicate regularly with the school nurse and/or trained diabetes personnel regarding any observations or concerns about the student.

•Always allow the student to check BG and/or ketone levels. Make sure that BG monitoring equipment (or continuous glucose monitoring [CGM]) is available at all activity sites and encourage the student to keep personal supplies readily accessible.

●Management of hyperglycemia:

•If glucose levels are elevated above a certain threshold of hyperglycemia (>250 mg/dL) or if the student develops nausea, remind them to test blood ketone levels [120].

•Management of mild or moderate hyperglycemia before or during exercise is described above [120]. (See 'Initial approach based on blood glucose and ketones' above.)

•Exercise is contraindicated if glucose is markedly elevated (≥350 mg/dL [19.4 mmol/L]) or if significant ketonemia or ketonuria are present, even with lesser degrees of hyperglycemia.

●Management of hypoglycemia:

•Be aware that hypoglycemia can occur during and after physical activity and that a change in the student's behavior could be a symptom of hypoglycemia.

•Be aware that hypoglycemia should be treated immediately with a fast-acting form of glucose (for adolescents, 15 grams of fast-acting carbohydrate, such as four glucose tablets or hard candies; for younger children, 10 grams may be sufficient). For youth receiving advanced insulin pump therapy with automated basal rate modulation (eg, predictive low glucose suspend [PLG] functionality), smaller amounts of carbohydrate ingestion may be sufficient. (See "Continuous subcutaneous insulin infusion (insulin pump)", section on 'Sensor-augmented insulin pump'.)

•Know where the fast-acting carbohydrate is located at all times (eg, first aid pack, backpack, attached to a clipboard, etc) during all physical activities, practices, and games.

•Consider getting authorization to use glucagon for emergency treatment of severe hypoglycemia. Use of this emergency treatment depends on individual factors, including school regulations. Intranasal glucagon formulations are now available that allow for ease of administration, using a single dose (3 mg) for all children ages four and older and adults [137,138]. (See "Hypoglycemia in children and adolescents with type 1 diabetes mellitus", section on 'Glucagon'.)

In the classroom, students should have fast-acting carbohydrate snacks readily available at all times, and students and their teachers should be instructed on the appropriate treatment of hypoglycemia (10 to 15 grams of carbohydrate, depending on size of the child or adolescent; wait 15 minutes and retest and retreat if necessary).

Every patient with T1DM should wear a medical identification bracelet or necklace (eg, MedicAlert) indicating the diagnosis of T1DM to ensure appropriate intervention by emergency personnel should such a situation arise. Patients can enroll in MedicAlert by calling (888) 525-5176 or through the internet at www.medicalert.org (United States) and www.medicalert.ca (Canada).

Camps — Specialized camps for children with T1DM provide a unique opportunity to share with and learn from others with diabetes and often promote a high level of physical activity. However, the incidence of hypoglycemia in such camps is high, with a median duration of approximately 1.7 hours per day based on a large assessment of youth using CGM [139]. The number of hypoglycemic events tends to increase with age and with physical activity effort [117]. If the expected level of physical activity at camp is higher than the child's usual level of physical activity, it may be helpful to reduce the basal insulin dose by 10 to 30 percent at the start of camp to help reduce the risk for hypoglycemia [117]. Since individual responses are highly variable, frequent BG monitoring (or CGM use) is recommended, including nocturnal measurements.

Management of a child with T1DM at a day camp is similar to management in school. If the camp is not specialized for children with T1DM, all camp staff who will be supervising the child should be educated about the risks and management of BG emergencies, and fast-acting carbohydrates should be available at all times. It is important to be aware that such camps will often provide a substantially increased level of physical activity as compared with the child's previous level of physical activity, that frequent glucose monitoring is important, and adjustment of insulin dose and carbohydrate intake are usually needed.

Scuba diving — Some controversy exists about the capacity for patients with T1DM to become certified divers. The National Association of Underwater Instructors prohibits individuals with T1DM from obtaining certification to dive through their organization due to safety concerns. By contrast, the Professional Association of Diving Instructors allows for individuals with T1DM to be certified. The Divers Alert Network reports that many active divers have T1DM and that the majority of divers do not experience dive-related hypoglycemia [140]. The United Kingdom Sports Diving Medical Committee supports allowing persons with T1DM to dive, as long as certain precautions are taken.

Studies that monitored BG concentrations during dives by individuals with T1DM indicate that scuba diving can be undertaken safely by experienced divers with well-controlled, uncomplicated T1DM, provided that appropriate precautionary measures are taken to prevent hypoglycemia [141]. Important precautions include rigorous pre-dive testing to determine glucose levels and rates of change before entering the water, a glycemic range of 150 to 250 mg/dL (8.3 to 13.9 mmol/L) before immersion, significant reduction of insulin doses (by 30 percent), availability of rapid-acting carbohydrates, and diving with a companion who understands how to recognize and treat a hypoglycemic reaction [142]. CGM may be useful to assist with glucose monitoring during scuba diving [143].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Diabetes mellitus in children".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: My child has diabetes: How will we manage? (The Basics)" and "Patient education: Managing blood sugar in children with diabetes (The Basics)" and "Patient education: Carb counting for children with diabetes (The Basics)" and "Patient education: Managing diabetes in school (The Basics)" and "Patient education: Giving your child insulin (The Basics)" and "Patient education: Checking your child's blood sugar level (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Benefits and risks of exercise – Regular exercise has important health and social benefits for children and adolescents with type 1 diabetes mellitus (T1DM). These individuals should be encouraged to engage in a wide variety of physical activities, with minimal restrictions but with careful management to avoid the associated risks for hypoglycemia and hyperglycemia. (See 'Benefits of exercise' above.)

●Glycemic effects of exercise – In individuals with T1DM, aerobic physical activity (such as walking, cycling, and general play) tends to lower blood glucose (BG) concentrations, while anaerobic physical activity (such as sprinting, hockey, or weightlifting) tends to increase BG concentrations (table 1 and figure 1). Many forms of team and individual sports and children's playground activities (such as soccer and other field sports, basketball, and baseball) consist of mixed aerobic and anaerobic activity. (See 'Exercise physiology' above.)

●Clinical implications – Children and adolescents with T1DM are at risk for hypoglycemia, which may occur during and immediately after exercise or may be delayed for several hours and occur during sleep. Conversely, exercise also can cause hyperglycemia in certain circumstances, especially during high-intensity anaerobic exercise such as sprinting, and in individuals in poor metabolic control. (See 'Hypoglycemia' above and 'Hyperglycemia' above.)

●Management – The following protocols are important to avoid dangerous episodes of hypoglycemia and hyperglycemia during and after exercise:

•Prior to exercise – The BG or sensor glucose (SG) concentration should be checked prior to exercise. The target range for glucose prior to exercise is between 90 and 270 mg/dL (5.0 and 15 mmol/L). If glucose is elevated to ≥270 mg/dL (15 mmol/L), the patient should check for ketosis, ideally using a point-of-care test for blood beta-hydroxybutyrate (BOHB).

-If ketones are very elevated (eg, BOHB >1.5 mmol/L), or hyperglycemia is severe (glucose ≥350 mg/dL [19.4 mmol/L]) irrespective of severity of ketosis, exercise is contraindicated. Patients with lesser degrees of ketosis may proceed with moderate exercise after correction of hyperglycemia and with close monitoring. Intense (vigorous) exercise should be deferred until BG/SG levels are restored. (See 'Initial approach based on blood glucose and ketones' above.)

-To prevent hypoglycemia during exercise, interventions include consumption of additional carbohydrates just before and during exercise, reduction of the basal insulin dose prior to exercise, and/or reduction of the pre-meal insulin bolus for postprandial exercise (table 5). These interventions should be selected based on baseline glucose levels, the intensity and duration of the exercise, and the patient's past glucose response to exercise. (See 'Glycemic management during exercise' above.)

•During exercise – The glucose concentration should be monitored approximately every 30 minutes during the exercise and carbohydrate consumption (table 4) or insulin dose adjusted accordingly to maintain euglycemia.

-Continuous glucose monitoring (CGM) using a subcutaneous device is especially valuable for patients who are physically active. The SG measurement may lag behind changes in BG. Guidance for using CGM for insulin and carbohydrate dosing before exercise is summarized in the table (table 3). (See 'Blood glucose monitoring' above and 'Carbohydrate intake before and during exercise' above.)

-Hyperglycemia that occurs during exercise can be corrected with small amounts of rapid-acting insulin. However, caution is warranted because exercise increases insulin sensitivity, so the patient may also be at risk for delayed hypoglycemia. (See 'Hyperglycemia' above.)

-A hybrid closed-loop system (artificial pancreas) can be useful for glycemic control during exercise but requires a somewhat different approach to management. (See 'Hybrid closed-loop insulin delivery system' above.)

•Post-exercise – Delayed (nocturnal) hypoglycemia occurs in a substantial number of children with T1DM after engaging in exercise in the afternoon. Preventive interventions include more frequent monitoring of BG/SG during the recovery period and before bedtime, ensuring that a bedtime snack is consumed, and, in some cases, reducing the basal insulin infusion in the evening. (See 'Delayed (nocturnal) hypoglycemia' above and 'Insulin pump' above.)

●School setting – Students with T1DM should fully participate in physical education classes and team sports at school, provided that there is good communication and collaboration between the student, his or her health care provider and parents, the school nurse, and the physical education instructor or team coach and good adherence to a well-designed regimen for glycemic control during and after exercise. The supervising staff must be trained to recognize and treat hypoglycemia (table 2), and the student should have ready access to BG monitoring equipment (or CGM) and fast-acting carbohydrates. (See 'Schools' above.)