Physical Activity Management for Youth With Type 1 Diabetes: Supporting Active and Inactive Children

World Health Organization guidelines (5) recommend that children and adolescents should do at least 60 minutes/day of moderate- to vigorous-intensity, primarily aerobic PA across the week. The guidelines recommend the addition of vigorous-intensity aerobic activities and activities that strengthen muscle and bone on at least 3 days/week. The guidelines also recommend that children and adolescents limit the amount of time spent being sedentary, and particularly the amount of recreational screen time.

Regular PA for youth with type 1 diabetes is important for its benefits to glycemic control, insulin sensitivity, cardiovascular and cardiorespiratory fitness, muscle mass and strength, and bone mineral density (6–12). There is also evidence of a direct association between regular PA and longer partial remission in youth with newly diagnosed type 1 diabetes (13). To promote regular PA in youth with type 1 diabetes, it is important to understand that youth may engage in different PA patterns based on their age and sex. For example, for very young children, PA typically occurs as multiple short bouts of activity that are unplanned, unstructured, and dispersed across the day (14,15). In school-aged children and adolescents, PA occurs both spontaneously and as planned structured events, such as physical education classes, sports practices, and/or competitions (16,17).

In all youth, studies consistently show higher PA in boys than in girls (18). Similarly, in youth with type 1 diabetes, studies have found higher PA levels in boys than in girls (19–21). Recent data also suggest age-related declines in PA, with the steepest decline occurring during the transition from elementary to middle school (i.e., between the ages of 10 and 13 years [18]), when youth may lose access to school recess or experience the withdrawal of parental and peer support for PA (22). Few studies have examined whether youth with type 1 diabetes experience a similar age-related decline in PA; however, in the SEARCH for Diabetes in Youth study (23), older youth with type 1 diabetes reported less vigorous PA and lower sports team participation than their younger peers. It is thus helpful for HCPs to consider these general and diabetes-related PA patterns in youth to effectively counsel families on a PA program, and—importantly—to promote persistent activity through adolescence, when many youth experience challenges attaining their target A1C, become more susceptible to diabetes complications, and encounter the insulin resistance of puberty (24).

Exercise, by definition, is a subset of PA that is planned, structured, and repetitive and that leads to improvement in or maintenance of physical fitness (25). In general, these activities can be classified as predominantly low- to moderate-intensity and thus aerobic-based (e.g., dancing, swimming, running, bicycling, and skateboarding) or intermittent- to very-high-intensity–based (e.g., sprinting, hockey, and racquet sports) activities, which may include anaerobic efforts. Exercise intensity occurs on a continuum, but this classification is helpful to understand the differences in fuel substrate utilization and metabolism, although in almost all forms of exercise, aerobic and anaerobic energy systems contribute.

Briefly, energy production to fuel low- to moderate-intensity aerobic-based activities is obtained through the oxidation of lipids (i.e., free fatty acids and muscle triglycerides) and carbohydrates (i.e., blood glucose and muscle glycogen) via β-oxidation and glycolysis, respectively (26,27). However, with very-high-intensity, short-duration, or anaerobic activity, energy production is obtained from anaerobic glycolysis, phosphocreatine, and free adenosine triphosphate (28). Resistance exercise also relies mostly on anaerobic sources of fuel and elicits very similar hormonal and metabolic responses to that of very-high-intensity and anaerobic exercise (29,30).

In youth, most forms of exercise, organized sports, general play, and daily PA comprise a combination of aerobic and anaerobic metabolism, which is why a general understanding of the physiology of exercise and diabetes is important for exercise planning. Figure 1 is a helpful guide and education tool that can be used when counseling parents and youth about exercise and diabetes management (31).

Aerobic-based, low- to moderate-intensity activities tend to lower blood glucose both during (typically 20–60 minutes after onset) and after exercise (32), with the highest risk for hypoglycemia likely occurring at about 50% of V̇O_2max (33), equivalent to moderate intensity. Additionally, after exercise, insulin sensitivity is increased for up to 24 hours, counterregulatory hormone responses may be impaired, and depleted glycogen stores are restored, which can predispose to hypoglycemia (32).

In contrast, for high-intensity exercise, there is a tendency to experience increasing blood glucose levels during exercise and up to 1–2 hours into recovery (34), because insulin levels do not rise in the portal circulation to compensate for the rise in circulating catecholamine levels and resulting in an increase in hepatic glucose production. This effect is particularly prominent if the activity is done early in the day with little to no prandial insulin in circulation and if the activity is specifically anaerobic-based (35). Also, despite the occurrence of hyperglycemia, there remains the risk of hypoglycemia in the subsequent hours post-exercise resulting from increased insulin sensitivity and depleted glycogen stores (35).

For resistance exercise, there is the tendency to experience more stable glucose levels both during and after exercise than with continuous moderate-intensity aerobic exercise (36–40).

As noted earlier, most of the exercise performed by youth may be characterized by repeated bouts of relatively intense activity interspersed with low- to moderate-intensity activity or rest (15–17). In the context of type 1 diabetes, this type of mixed-intensity activity can result in smaller declines in glycemia compared with continuous moderate-intensity exercise, both during and after exercise (35). Also relevant to youth with diabetes are recent findings linking stress hormone responses associated with competition and intensive exercise to increasing glucose levels, though with no apparent impact on recovery and post-exercise glucose levels (M.C. Riddell, personal communication).

Although we recognize that it is already challenging to cover the many aspects of diabetes self-management in routine clinic visits, we still encourage HCPs, as a core practice, to include exercise in each consultation. The following approach may provide a useful structure (41).

Most clinicians are used to building a picture of the families for whom they provide care. This usually includes family structure and support systems. We believe it is equally important to collect information on lifestyle behaviors and priorities in families with type 1 diabetes. This helps to identify opportunities to motivate youth to engage in PA and to codesign strategies to reduce sedentary behaviors.

Barriers to participation in PA and exercise exist for all youth, and those with type 1 diabetes are no exception. However, in addition to understanding general barriers (e.g., time, work, access to facilities, lack of motivation, negative body image, embarrassment, and weather [42]) that may prevent greater uptake of PA, it can help to identify barriers unique to youth with type 1 diabetes. These can include recurrent hypoglycemia and/or fear of hypoglycemia, elevated A1C and/or elevated glycemic variability, the stigma of having diabetes, required planning, parental hesitancy, and a general lack of knowledge in the field of exercise and diabetes (11,42–44). These barriers are summarized in Table 1.

Understanding how these barriers affect participation in PA and exercise may help when providing age-appropriate counseling. For example, if the stigma of having diabetes is a barrier to PA for a child, it may help to inquire about the source of this barrier, as educating an adult (e.g., a teacher or coach) about diabetes may help. Similarly, if a child fears stigma from his or her peers, it may help to identify a supportive friend with whom to exercise. If recurrent hypoglycemia is a barrier, then it is possible that a personalized exercise plan and the addition of diabetes devices (e.g., continuous glucose monitoring [CGM], insulin pump, and/or automated insulin delivery [AID] system) may help. Or, if fear of hypoglycemia is a barrier, then it may help to refresh parental and youth knowledge regarding hypoglycemia treatment or to refer the family for cognitive behavioral counseling to address this fear (45,46).

In this discussion, it can also be helpful to learn about any facilitators of PA and exercise. While the literature regarding potential facilitators of exercise in youth with type 1 diabetes is limited, there is anecdotal evidence suggesting that active parents are more likely to support child PA than less active parents (47). For younger children, parents who are physically active can serve as positive role models (48), while for adolescents, active parents may be able to minimize barriers to PA or model social connectedness through PA (49). Clinicians’ confidence to discuss exercise and their own interest in PA has also been shown to have an influence on adults with diabetes (50).

Once familiar with the family’s pattern of PA and potential barriers and facilitators of PA for the youth with type 1 diabetes, it is possible to develop a personalized PA plan. To guide this step, we find it helpful to use the structure shown in Figure 2, starting in the center and systematically moving outward (41).

Thoughtful goal-setting can help to promote safety and sustainability when starting a new PA program. For example, it is important to consider a youth’s baseline fitness, as low baseline fitness may initially increase the risk of exercise-associated hypoglycemia and is associated with increased glycemic variability in youth with type 1 diabetes (51). To help youth sustain an active lifestyle, it is important to set initial PA goals that are realistic and to consider any diabetes-specific barriers that may threaten consistency. Goals vary and may include a desire for increased fitness, improved body composition, weight management, social inclusion such as peer activities or team sports, better glycemic control, or elite performance. Clarifying the goal will help to direct the approaches.

Weight management is a common goal of exercise, particularly in the adolescent age-group. In this scenario, recommending insulin adjustments to avoid hypoglycemia and reduce the need for extra carbohydrates may be both a realistic place to start and a change that promotes sustainability. If improved fitness is an identified goal for a youth with type 1 diabetes, it is important to encourage stepped exercise goals, discuss anticipated changes in insulin sensitivity that will likely occur with increasing exercise training, and discuss subsequent reductions in total daily insulin dose that may be needed to avoid hypoglycemia (41).

For some young people, an initial PA goal may be to re-engage with sports lessons at school or simply to be more active. For these youth, it may be realistic to initially have them target performing exercise a few days per week and focus on hypoglycemia prevention and minimizing time spent away from the activity because of diabetes management (41). Alternatively, the goal for youth participating in competitive sports may be optimal exercise performance; consulting a dietitian would be suggested to formulate a plan that optimizes fuel intake (i.e., carbohydrate and protein intake) and insulin administration based on their level of insulin sensitivity and exercise intensity and volume (33,52). For youth athletes with type 1 diabetes, it may also be necessary to consider separate plans for training and competition, and it is important for coaches/trainers to know about diabetes management and any specific plans (41).

Type, intensity, and duration of exercise will affect acute glycemic excursions in youth with type 1 diabetes (53); thus, these are relevant when considering barriers to initial uptake and maintenance of PA goals. If youth and parents do not know basic exercise physiology around diabetes, showing them Figure 1 may help with this discussion (31,33). As mentioned earlier, general aerobic activity such as a steady jog or a bike ride lasting >30 minutes can be predicted to result in a drop in blood glucose levels (32). It is important for youth and parents to know this so they can take precautions to avoid hypoglycemia. In contrast, very-high-intensity exercise frequently results in acute hyperglycemia (34,35), especially in the fasted state, and youth and parents may appreciate anticipatory guidance as well as the opportunity to test whether adding a cool-down period or components of low-intensity aerobic activity can help with managing hyperglycemia after high-intensity exercise (54). Of note, for PA lasting <30 minutes, it is reasonable that youth with type 1 diabetes may perceive minimal acute impact on their glucose levels. Some youth with type 1 diabetes may appreciate hearing this information to help them set realistic expectations when starting a new PA program. However, because the risk of hypoglycemia increases with exercise duration because of glycogen depletion (32) and ongoing muscle glucose uptake, it is important that youth and parents know that, even at low intensity, prolonged exercise may require precautions to avoid hypoglycemia.

Because exercise and PA are likely to occur spontaneously in youth and with some level of active insulin on board (IOB), it is crucial to discuss insulin action times with youth and parents and how IOB can affect glycemic responses to exercise. It is easiest to manage glucose levels and exercise when minimal or no active rapid insulin is in the circulation. Still, in our experience, this is an uncommon scenario in youth, who are unlikely to exercise before their first dose of prandial insulin of the day.

Likewise, for exercise occurring 1–2 hours after a meal, it may be reasonable for some youth to consider a prandial insulin dose reduction of 25–50% based on the impact the activity is predicted to have on blood glucose and the planned duration of PA, if this is known. Although aggressive reductions in prandial insulin >90 minutes before exercise may reduce the risk of hypoglycemia during or immediately after exercise, they can be associated with hyperglycemia before exercise commences, so these possible outcomes must be balanced and prioritized according to the youth’s identified PA goals. Also, it may not be advisable for youth using a hybrid closed-loop (HCL) or AID system to modify insulin and carbohydrate intake for exercise because the algorithms supporting the delivery of insulin in these systems are designed to respond automatically to even mild hyperglycemia (55).

Because the amount of carbohydrate to maintain euglycemia during exercise is determined by insulin levels, when only basal insulin is active, it may be possible to avoid hypoglycemia with carbohydrate intake totaling 0.3–0.5 g/kg/hour, with ingestion occurring every 20–30 minutes. However, when exercise coincides with peaking rapid-acting analog insulin (33), youth may need to consume double this amount of carbohydrate or more to avoid hypoglycemia. Additionally, it may be helpful for parents and youth to create a list of preferred and suitable carbohydrate options based on PA goals, keeping in mind that, when elite performance is the desired goal, evidence suggests that higher carbohydrate intake is optimal.

Finally, for in-depth discussions of planned exercise, there is evidence that afternoon exercise of any intensity is associated with greater risks of delayed nocturnal hypoglycemia, frequently seen between 7 and 11 hours later (56). Thus, depending on the regimen used, a temporary reduction in basal rates or the setting of predictive glucose suspension modes in youth using an insulin pump, or an adjustment to the evening basal insulin dose in those using injections, may be required. Additionally, youth should be reminded that, even with afternoon high-intensity exercise that causes acute hyperglycemia, there is still a risk of delayed nocturnal hypoglycemia.

It is important to question youth about their typical glycemic response to exercise and history of hypoglycemia. This is because recent hypoglycemia before exercise is associated with an increased risk of further hypoglycemia (57) due to attenuated counterregulatory responses and glycogen depletion. Although uncommon in youth, impaired hypoglycemia awareness needs to be considered and included in a final action plan, as this may further increase the risk of hypoglycemia after exercise. This risk may be especially pertinent during sleep, which is associated with impaired counterregulation in youth with type 1 diabetes (58).

Another safety consideration specific to youth with type 1 diabetes is exposure to increased PA for several days in a row, such as during an active camp. In this setting, the short-term increase in insulin sensitivity resulting from PA will almost certainly require successive reductions in total daily insulin on consecutive days of increased activity.

Finally, it is ideal in subsequent exercise consultations to review PA plans and make any necessary modifications. Initial insulin dosing or carbohydrate strategies are typically based on consensus or informed by clinical studies and may require individualization and fine-tuning. Likewise, individual responses to exercise vary widely (59), and PA goals may change as youth grow, their fitness improves, and/or their insulin replacement modality changes. Therefore, a review cycle incorporating all these factors should occur as required in the clinic setting, or more frequently, if necessary or desired (41).

Diabetes education provided during the new-diagnosis period of type 1 diabetes offers the opportunity to encourage and support an early return to regular PA and exercise for youth. Although, traditionally, PA has not been a feature of diabetes education for the newly diagnosed, the 4T study (60) is currently testing a structured approach to incorporating exercise from diagnosis, and the authors recommend that similar approaches be considered in all diabetes services.

Diabetes education during the new-diagnosis period can also be a time to minimize the development of hypoglycemia fear in both parents and youth. Recent data show that there is no longer an increased risk of severe hypoglycemia with near-target glycemic levels, and this is an important message for families to understand (61). Furthermore, where CGM is available, the risk of severe hypoglycemia is markedly reduced with real-time data and alert functions (62).

School teachers may be hesitant to allow children with newly diagnosed type 1 diabetes to return to their usual sports and PA. Therefore, it is important to include information on exercise as part of a school education program for newly diagnosed youth to address these concerns proactively (63).

New diabetes technologies for youth have expanded considerably in recent years, and the investigation of the utility of these new devices under exercise conditions has become more common and increasingly important. However, not all technology is available in all countries, and disparities in access to technology persist.

Glucose monitoring remains a cornerstone of exercise management and diabetes, and CGM is strongly recommended as the optimal method in recent consensus guidelines (64). Interstitial fluid glucose levels as measured by CGM systems at steady state show minimal variance from capillary blood glucose levels; however, under aerobic exercise conditions, CGM can lag in registering changes in blood glucose by 12 ± 11 minutes, and this appears to occur both as glucose levels decline during exercise and as they recover post-exercise (65). Thus, confirmation of low glucose levels by fingerstick glucose testing may be required if CGM values approach hypoglycemia, if the risk of imminent hypoglycemia is noted, or if symptoms and CGM values do not align (4,65,66).

CGM systems also provide trend data to inform further management during and after exercise. The absolute real-time value and associated trend arrows can be combined to inform the intake of small frequent amounts of carbohydrate to proactively maintain CGM glucose values in the exercise target range, where a safe compromise between acute hypoglycemia risk and excessive hyperglycemia can be found. For most youth, this range is 120–180 mg/dL. Clinicians should be familiar with this target glucose range as a suggested starting point for exercise and should incorporate steps to maintain glycemia within this range during exercise in PA plans for youth. Weight-based strategies for carbohydrate intake using CGM trends have been published, and although they require further refinement for accuracy and safety, they provide a useful framework for HCPs and youth (66).

Insulin pumps can promote glycemic management during and after exercise, and HCPs should encourage youth with type 1 diabetes to consider using a pump if resources allow. For example, basal rate adjustments or pump suspensions have been shown to be effective for reducing the risk of hypoglycemia during exercise (67) but should be done up to 90 minutes before exercise for maximal hypoglycemia protection (68). Relatedly, the widescale uptake of HCL and AID systems in youth with type 1 diabetes now offers the opportunity to study their use during exercise (69). Equally, as the algorithms driving decisions around insulin delivery vary among these systems, it is important for HCPs to have a basic understanding of the options available in each system to manage the exercise environment (70).

Exercise is contraindicated for youth with type 1 diabetes in certain scenarios, including after an episode of severe hypoglycemia in the previous 24 hours, with hyperglycemia with a blood ketone level ≥1.5 mmol/L, or with acute injury or infection. Youth with type 1 diabetes have reported challenges with participation in community sports because coaches are often volunteers with no or very limited training on what special precautions of care youth with diabetes require (71). Educational resources specifically tailored for sports coaches are needed. Elite or competitive athletes require a more sophisticated approach to the management of diabetes, and, anecdotally, their approach is often based on their own personal experience. However, when possible, referral of such youth to a specialized team is recommended.

PA is a core component of the management of youth with type 1 diabetes. It is essential for HCPs to develop comfort with the basics of exercise management and the evidence base around specific strategies that can increase exercise participation, enjoyment, and overall safety for youth. A structured approach incorporating a framework for management based on glucose monitoring, carbohydrate intake, and insulin management may support youth and families in applying advice provided in the clinical consultation to daily PA (41). Diabetes technology, especially CGM, may offer additional benefits for youth around exercise (55,72).

The authors acknowledge all of the young people living with type 1 diabetes who have participated in research studies that have contributed to advancing the evidence and knowledge that support youth with type 1 diabetes in exercising and maintaining PA.

No potential conflicts of interest relevant to this article were reported.

E.A.D. planned the manuscript sections and wrote the initial manuscript. V.B.S., S.Y.M.T., R.J.L., S.R.P., and C.E.T. reviewed and edited the manuscript and approved the final version before submission. E.A.D. is the guarantor of this work and, as such, takes responsibility for the integrity and accuracy of the content.