Impact of resistance exercise in type 1 diabetes pediatric patients

Abstract

Type 1 diabetes mellitus (T1DM) is an autoimmune condition whose prevalence is prominent in children and adolescents, resulting in insulin deficiency with a potential for long-term complications induced by glucotoxicity. As an autoimmune disease where the body's immune system attack insulin-producing beta cells in the pancreas, leading up to complete or near-complete inability to control the blood glucose levels independently. The lack of glycemic control calls for lifelong exogenous insulin administration in conjunction with careful monitoring to control blood sugar levels and prevent acute and chronic health issues complications. Regular physical activity, notably resistance exercise (RE), may be beneficial in the glycemic management of this population, enhancement of muscle strength, and general health for the growing, development and maturation in children. The evidence depicting its benefits and safeguard for RE in pediatric T1DM patients remains underexamined. This mini-review seeks to synthesize qualitatively the current evidence on RE regarding its global effects on the T1DM in children. A search for peer-reviewed papers is carried out through primary databases, centering on publications that examined the physiological, metabolic, and psychosocial consequences of RE in children with T1DM. Emerging evidence indicates that RE is one potential method of safe and efficacious intervention to improve glycemic management, physical capacity, and quality of life. However, there is still some reluctance to this type of training in the pediatric population. The available research has not only refuted the belief that strength training was contraindicated in the pediatric population but also recommends its systematic practice to enjoy its benefits on the three spheres of health. Nevertheless, methodological differences and small population studies pose challenges to drawing firm conclusions. The review underscores other areas, including the need for standardizing protocols for including patients such as follow-ups and greater considerations for psychosocial effects of RE in this population. This minireview underlines the importance of RE in a global approach to pediatric diabetes care by providing practical insight for both clinicians and researchers.

Key Words: Type 1 diabetes; Strength training; Children; Glycemic control

Core Tip: Progressive resistance training protocols in pediatric diabetes not only enhance muscular performance but also offer secondary health benefits. Although the effects of strength training on glycemic control outcomes remain variable there is a trend toward improvement. Furthermore, it can act as a foundational stimulus to encourage greater overall physical activity, which may further support glycemic regulation. Additional benefits include increased strength, improved posture, and enhanced motor control.

INTRODUCTION

The prevalence of type 1 diabetes mellitus (T1DM) has been increasing since the 20^th century. For instance, Onkamo et al[1] reported that the global incidence was projected to rise by approximately 3% per year. T1DM constituting a public health problem with increasing projection[2].

T1DM is a metabolic disorder characterized by a complete cessation of insulin secretion by autoimmune-mediated lysis of pancreatic beta cells that leads a chronic hyperglycemia besides changes in the metabolism of lipids and proteins[3]. During long term diabetes is associated with complications, including an increased risk of cardiovascular disease, nephropathy, and neuropathy[4], associated with exercise-induced hypoglycemia and hyperglycemia.

Overall, T1DM has a profound impact on patients' health and quality of life in children[5]. For this reason, organizations such as the American Diabetes Association (ADA) include physical activity as a fundamental component of the therapeutic approach to counteract these complications[6].

Physical exercise as change in lifestyle in T1DM is considered of critical importance—particularly within the pediatric population. The ADA emphasizes that structured physical activity, including resistance training, yields significant metabolic and psychological benefits in children with T1DM[7]. At the same time, it highlights the need for caution due to the potential risks associated with exercise-induced hypoglycemia and hyperglycemia.

Moreover, emphasis is placed on the fact that regular physical activity does not increase the risk of severe hypoglycemia in pediatric patients[8], an important consideration given that fear of hypoglycemia is often cited as one of the main barriers to engaging in physical activity among children with T1DM[9]. Specifically, in pediatric populations, it has been reported as the second most common barrier, following school schedules[10].

However, some results reported showed that an intermittent and continuous aerobic exercises are associated with a lowering of glycemia in male adolescents with T1DM, but after resistance training intervention the glycemia remained stable without significant alterations. These findings hold important implications related to clinical exercise advice and disease management in adolescents with T1DM[11].

Although cardiovascular training has traditionally received greater importance emphasis in the management of this metabolic condition, it is well established that T1DM can impair both the response to and the capacity for aerobic exercise[12]. This impairment is primarily attributed to autonomic nervous system dysregulation at rest and during exercise[12], as well as to mitochondrial dysfunction, which directly affects skeletal muscle tissue[13]. In pediatric populations, additional disruptions have been reported in inflammatory, oxidative, and metabolic responses[14].

On the other hand, it is well established that T1DM induces alterations in otherwise healthy skeletal muscle tissue, leading to reductions in muscle mass and strength, as well as dysregulation in glucose, lipid, and protein metabolism[13].

These alterations are also evident in pediatric populations, although to a lesser extent when adequate glycemic control is achieved. This physiological disturbance has clinical implications, particularly in terms of force-generating capacity, which is consistently reported to be lower in individuals with T1DM compared to their healthy peers. This documented phenomenon has led to the hypothesis of accelerated muscle aging induced by T1DM[13], a finding that has also been corroborated in pediatric populations[15].

If this strength deficit emerges in the early stages, it tends to progressively worsen over time, becoming particularly severe with the onset of neuropathy[13]. For this reason, the implementation of combined or concurrent exercise (aerobic plus resistance training) has been investigated, as it may reduce the risk of developing cardiovascular risk factors, improve glycemic control, lower insulin requirements, enhance physical fitness, and improve quality of life in individuals with diabetes[16]. For example, the positive effects of concurrent training in the glycemic control has been reported when patients uses concurrent training, because when strength training is added to aerobic training the effective in reducing IG fluctuations is greater that where compared in isolate aerobic o resistance training alone suggesting that the combination activate the metabolism and the anabolic adaptation that improve the glycemic control (i.e., glucose levels) and the muscle health[17].

Eventually, it has been reported that an isolated supervised progressive resistance training two-times a week in children with T1DM must last at least 32 weeks to get a significant decrease in blood glucose level glycated hemoglobin (HbA1C). In addition, exercise-induced increase in adiponectin improves insulin sensitivity[18]. This suggests that long-term isolated resistance training can have substantial metabolic benefits.

The metabolic improvements can be attributed not only to the increased metabolic demand induced by exercise, but also to the fact that muscle contractions during physical activity enhance cell membrane permeability, exerting an insulin-like effect that promotes greater sensitivity to exogenous insulin[19].

Therefore, incorporating strength training during the pediatric stages in children with diabetes serves a dual purpose and is of great importance to maintain adequate strength levels. Firstly, it helps to mitigate functional decline, and secondly, it promotes the achievement of moderate-to-vigorous physical activity (MVPA) by enhancing motor competence and performance[20]. Increasing MVPA has been associated with better glycemic control than fitness alone. These findings highlight the need to develop strategies aimed at increasing MVPA as a foundation for improving glycemic control in individuals with diabetes[21].

Consequently, it is important to further investigate the effects of resistance strength training on the health and quality of life of children with T1DM, as there is evidence suggesting that it helps to support glycemic control, as well as maintain and improve skeletal muscle morphology and function favoring an increase of MVPA.

Collectively, these findings suggest that strength training may serve as a safe and effective approach for pediatric patients with T1DM. Given the importance given the interest in increasing the health and quality of life in the pediatric population with T1DM, a comprehensive and exploratory minireview is warranted to critically evaluate its safety, efficacy, and benefits. Our primary research question is: Is resistance training beneficial for glycemic control (HbA1c or glycemia levels) and health in children with T1DM?

This minireview synthesizes current evidence on strength training in children and pre-adolescents with T1DM populations.

LITERATURE SEARCH

The primary research question was “Is resistance training beneficial for health in children with T1DM?” Inclusion criteria for papers included in this minireview were: (1) To be < 18 years old; (2) with diagnosis of T1DM; (3) Intervention consisted in isolation, supervised or unsupervised with resistance training in any kind of form (calisthenics, barbells, dumbbells, medicine balls etc.,); and (4) At least 6-weeks of intervention. We excluded papers if they: (1) Involve animals; (2) Included dietary intervention; (3) Acute interventions; and (4) Include concurrent training.

The main outcome that was contemplated was glycemic control (HbA1c or glycemic status). The secondary was the impact on skeletal muscle (strength, hypertrophy) as well as functionality (e.g., jump) and motor competence (functional tests), and the occurrence of adverse events (hypoglycemia).

Two reviewers independently conducted an individualized search strategy for PubMed, Scopus and Web of Science database using descriptors related to diabetes mellitus type 1, strength training, and children. Two reviewers independently screened the titles and abstracts to decide if met the inclusion criteria. If any discrepancy was found were revolved by discussion between the two reviewers in case of not reaching a consensus, the participation of another reviewer was involved. With final list of manuscripts (n = 3), the full text was retrieved and read in their entirety for data extraction.

RESULTS

In Table 1 has been summarized the main information extracted for the retrieved articles.

Table 1 Main information for the retrieved articles.

Ref.	Sample (n)	Resistance training intervention	Control	Periodization	Primary outcome: Glycemic control	Main results	Secondary outcomes
Petschnig et al[18], 2020	n = 21. Allocated in 2 groups: (1) Strength training n = 11; 11.00 (0.8) years; with 2.63 (1.85) years of duration of diabetic history; and (2) Control group n = 10; 11.30 (0.7) years with 2.80 (2.07) of duration of diabetic history. Diagnosed at least in the last 6 months. No regular sport more often than once per week and sports lessons in school not more than twice a week	8 exercises for main muscle groups in a circuit; 25-40 seconds per exercise at 30% RM; 30-40 seconds resting; 2-times	No exercise	32 weeks; twice a week	HbA1c; glycemia before after each session	CG HbA1c; Baseline: 7.84 (1.38); At 17 weeks: 8.26 (1.26); At 32 weeks: 8.72 (1.33). ST HbA1c; Baseline: 8.75 (1.37); At 17 weeks: 8.55 (1.33); At 32 weeks: 8.75 (1.37). Glycemia before and after each session showed a significant reduction after each session 26.5 (4.4%). No adverse effects reported	Adiponectin; strength tests: (1) Seated bench press; (2) Seated bench pull; and (3) Seated leg press. Echocardiogram left common carotid artery
Särnblad et al[11], 2021	n = 8. 17.5 (0.8) years; 8.1 (4.8) years of diabetes duration	2 blocks; Interspersed 2 minutes; Each block included 3 sets until muscular failure at 70% 1 RM with 2 minutes of resting in lying leg press, lying leg curl and seated leg extension	Aerobic continuous; aerobic intermittent	Acute	Glycemia	Baseline: 11.8 (3.8) mmol/L; 5 minutes before exercise: 11.6 (3.8) mmol /L; exercise start: 11.5 (3.2) mmol/L; changes 0-45 min exercise: -1.0 (1.4) mmol/L; at end of recovery: 11.6 (3.9) mmol/L	Lactate; saturation of O2
Ramalho et al[22], 2006	n = 6; 19.8 ± 5.1	8 exercises in machine: Chest press, bicep curl, triceps extension, lower back, abdominals, leg press, leg curl and leg extension, 3 sets, 8-12 repetitions, 60%-80% 1 RM (60 seconds of rest)	Aerobic exercise	12 weeks; 3 days per week	HbA1c; glycemia; insulin dosage	There was no change in the parameters evaluated, only a reduction in insulin dosage after exercise. 0.95 (0.34) vs 0.79 (0.28)	Anthropometry

CG: Control group; ST: Strength training; HbA1c: Glycated hemoglobin; RM: Repetition maximum.

DISCUSSION

The aim of this mini-review was to examine the effects of isolated resistance training on glycemic control in children with T1DM. The analyzed data showed a trend agreed with previous data of resistance training in adults, the RT let manage the glycemic control and increase strength fitness[22,23]. Additionally, other potential benefits can be inferred by the adult’s studies and pediatric resistance training studies (Figure 1). The findings reveal a clear paucity of research in this area. Despite methodological heterogeneity and limitations related to small sample sizes, the available studies demonstrate consistent and clinically relevant physiological patterns.

Figure 1 Holistic effects of strength training on children with type 1 diabetes mellitus.

To date, only two studies have investigated the long-term metabolic effects of resistance training on HbA1C, yielding contradictory results. Petschnig et al[18] reported an improvement in HbA1c after 17 weeks of training, which, however, returned to baseline levels by week 32. In contrast, Ramalho et al[22] found no significant changes in this parameter. Nevertheless, both studies reported noteworthy metabolic adaptations. Petschnig et al[18] observed an approximate 25% reduction in post-exercise blood glucose, suggesting an acute enhancement in peripheral glucose uptake—likely mediated by insulin-independent mechanisms, particularly the contraction-induced translocation of GLUT-4. Although this acute effect is transient, sustained training adherence could lead to cumulative benefits over time, potentially contributing to long-term HbA1c reduction.

Additionally, Ramalho et al[22] reported a significant reduction of approximately 20.25% in daily insulin dosage, indicating improved insulin sensitivity. Conversely, the study by Ramalho et al[22] did not report significant changes in HbA1c or fasting blood glucose.

A third study assessed the acute glycemic response to resistance exercise, analyzing blood glucose kinetics. This investigation confirmed that high-intensity resistance training (70% 1RM to failure) induces a moderate decrease in blood glucose during exercise (-1.0 ± 1.4 mmol/L), with no significant changes observed during the post-exercise recovery phase[11].

In an overall perspective these results show similar trends have been observed in adolescent populations, as reported in previous research’s as for example by Saki et al[24]. In their study, three groups were compared: A T1DM control group, a healthy control group, and a T1DM group undergoing concurrent training. The training protocol consisted of REs followed by aerobic training, performed three-times per week over a 12-week period. The results demonstrated improvements in glycemic control as well as enhancements in heart rate variability, suggesting favorable metabolic and autonomic adaptations in response to the intervention.

Likewise, Farinha et al[25] reported improved glycemic control (before-after intervention) in a cohort of young adults with T1DM (mean age 22 years) who underwent a 10-week resistance training program, performed three-times per week. However, the study found no significant differences between training modalities—resistance training, high-intensity interval training, and concurrent training—when analyzing the effect over time. Specifically, there were no significant changes in HbA1C, lipid profile, fasting glucose levels, or body composition across groups. Nevertheless, longer-term studies are needed to confirm the findings reported by Farinha et al[25].

Following a 12-week concurrent training program (combining resistance and aerobic exercise). However, a clinically relevant finding was the significant reduction in the required dose of exogenous insulin, which decreased from 0.95 to 0.79 U/kg/day. This outcome may indicate improved insulin sensitivity, although the study did not include direct assessments of insulin sensitivity or secretion. Furthermore, the relatively short duration of the intervention and the absence of an individualized progression strategy may have limited its potential impact on long-term glycemic markers such as HbA1c[24].

In most studies, secondary outcomes have been included, highlighting additional benefits beyond those related to metabolic control. reported a particularly notable increase in muscle strength, especially in the lower limbs or anthropometry[22].

However, it is important to emphasize that strength improvements during the pediatric age are of paramount importance. Participation in strength training programs during adolescence is associated with multiple Benefit, greater self-efficacy and enjoyment of exercise, both of which are strong predictors of higher physical activity levels in adulthood[26].

The cumulative evidence analyzed in a recent meta-analysis, indicates that the positive effects of resistance training have been consistently demonstrated when implemented concurrently aerobic or cardiovascular exercise, in HbA1c (SMD = -0.63) and in reduction in daily insulin needs (SMD = -0.79). As is well established, adopting an active lifestyle that includes resistance training during the pediatric stage facilitates the maintenance of this habit into adulthood. In this context, extensive evidence supports the beneficial effects of resistance training on glycemic control in individuals with T1DM during adulthood[27].

Moreover, concurrent training appears to help reduce a commonly perceived barrier to exercise in individuals with T1DM: The risk of hypoglycemia. The risk of hypoglycemia associated with resistance training in children and adolescents does not appear to be a major concern. For instance, data from Särnblad et al[11] showed that blood glucose levels remained stable in a sample of eight participants with a mean age of 17.5 (± 0.8) years during a resistance training session consisting of two rounds of three lower-body exercises (lying leg press, lying leg curl, and seated leg extension), each performed for three sets to muscular failure at 70% of 1RM. This glycemic stability was not observed during intermittent or continuous aerobic exercise, where a reduction of approximately 5 mmol/L in blood glucose was recorded[11]. In another similar paper, Nazari et al[28] in a group of 20 T1DM children [11.22 (1.90) years] concluded that in a concurrent exercise intervention during 16 weeks leaded a reduction in HbA1c [7.98 (1.02) to 7.83 (1.00)] and concomitantly the cortisol and anxiety was lower and the quality of life was improved.

Finally, it is important to note that despite the numerous reported benefits, certain comorbidities associated with T1DM must be carefully considered through appropriate pre-exercise screening. Conditions such as proliferative retinopathy or nephropathy represent clinical scenarios in which resistance training is generally not recommended due to the potential risks involved[29].

For future research, it is worth considering that the lack of improvement in HbA1c may be partly attributed to compensatory behaviors aimed at minimizing the risk of hypoglycemia. These may include increased carbohydrate intake around the time of exercise and/or reductions in insulin dosage, which should be closely monitored and controlled in study.

CONCLUSION

Isolated resistance training has been shown to improve glycemic control in pediatric patients with T1DM. However, the benefits appear to be even greater when resistance training is combined with other forms of exercise, such as aerobic training, in what is known as concurrent training. This combination not only enhances insulin sensitivity and metabolic regulation but also promotes spontaneous physical activity, which plays a crucial role in maintaining stable glycemic levels over time. Implementing resistance training at an early age may improve adherence to physical activity routines and foster long-term engagement in healthy behaviors. As a result, it increases the likelihood of sustained glycemic monitoring and control throughout the patient’s life.