Patients with type 1 diabetes usually present cardiovascular risk factors. Sixty percent of them are overweight or obese, 40% have hypertension, 60% have dyslipidemia, leading to cardiovascular disease as the major cause of death in adults with type 1 diabetes. Regular exercise can help patients to improve cardiovascular disease risk profile, metabolic control and chronic complications. Recommendations for exercise in children with diabetes are the same as the general population, between ages 8 to 18 years 60 min of physical exercise/day is suggested, including moderate or vigorous aerobic activity (at least 20 minutes), muscle strengthening and bone strengthening activities. Children with type 1 diabetes have poorer physical fitness levels than the non-diabetic peers and it has been described some barriers to meet these recommendations between children and adolescents with type 1 diabetes such as the fear of hypoglycemia, external temperature, work schedule, loss of control of diabetes, a low fitness level. The two types of exercise (aerobic and anaerobic) are recommended in people with diabetes. High intensity interval training involves alternation between brief periods of vigorous exercise and recovery at low to moderate intensity. Has been shown that HIIT is associated with improving aerobic capacity without a detrimental decline in blood glucose in adults with type 1 diabetes and home-based high-intensity interval training reduces barriers to exercise in the same group. The objective of the present study is to propose a HIIT exercise protocol through online modality to a group of adolescents with type 1 diabetes to evaluate the metabolic effects and physical capacity through an analytical, prospective and longitudinal study (before and after) for 3 months. As primary outcome is expected to improve metabolic control shown as an increase in time in range on continuous glucose monitoring and a decrease in glycosylated hemoglobin. And as secondary results, improve the aerobic capacity and resistance strength, lipid profile parameters, anthropometric and on the mood of the participants.

Hypothesis Three month HIIT training program increases time in range (TIR) and decreases glycemic variability (MAGE) in adolescents with DM1.

HIIT training program improves physical fitness (aerobic capacity and strength) of adolescents with DM1.

Methodology Analytical, prospective, longitudinal study (before and after). This type of study was chosen for ethical reasons. A group will not be left without intervention knowing the benefits of physical exercise in patients with DM1.

HIIT for 3 months

Population of study This study will be carried out with adolescents with type 1 diabetes treated at the sponsoring Hospitals: Las Higueras and Guillermo Grant Benavente.

A sample size of 30 Adolescents would be sufficient to detect a 15 percent increase in the percentage of time in the range of glucose values within the target range four months after the study start using a level of significance of 0.05% a power of 80% and a loss of follow-up of 15% (4 adolescents).

Type of sampling Convenience sampling

Procedures

Metabolic control monitoring Continuous glucose monitoring (CGM) will be used continuously during the study period. The duration of the CGM is going to be 7 days each time (Guardian Connect, Medtronic). If the patients are already wearing a CGM, will use the same device and data from these specific times will be collected for analysis.

Blood glucose will be monitored during exercise to make adjustments to therapy if necessary. This will be done by the doctors weekly for the first month and then every 15 days.

The statistical analysis of the continuous glucose monitoring (CGM) will be carried out in 4 moments: before starting the study, the first month after, at 3 months and 3 months after ending the training.

Blood sampling is going to be taken at baseline and at 3 month. will be measured HbA1c and lipid profile.

Total insulin dosing is going to be carefully recorded as units/kg/day during the study.

An insulin sensitivity score (ISS) is going to be calculated using the SEARCH ISS model: logeIS = 4.64725 - 0.02032 × (waist, cm) - 0.09779 × (HbA1c, %) - 0.00235 × (TG, mg/dL; R2 = 0.74 in the initial SEARCH model). This has been validated using the hyperinsulinemic euglycemic clamp, considered the gold standard for insulin sensitivity measures. CGM data are going to be downloaded and used to calculate percent blood glucose at, below, or above target.

The HbA1c and lipid profile will be measured using the Abbott brand model Architect c8000.

Nutritional assessment Nutritional consultation is going to be performed to the participants, in which it will be carried out a body composition analysis using the bioimpedianciometer TANITA TBF-40 at several times: before starting the intervention, at 1 month, at 3 months and at 3 months after finishing the intervention.

Two educational sessions will be performed to participants and parents and / or caregivers on carbohydrate content and glycemic index to reinforce the knowledge acquired throughout the course of the pathology in order to contribute to improve glycemic control. These will be carried out through a digital platform divided into groups of 10 or 15 participants.

In order to know the daily calorie intake and the distribution of macronutrients of the participants, the information from the 24-hour reminder questionnaire will be collected through a telephone call in 4 random days (without prior notice) during the same evaluation times mentioned previously.

Fitness monitoring Before intervention the participants are going to undergo physical evaluation: Cafra test, course-navette test, strength and Physical activity questionnaire for adolescents (PAQ-a) to determine their health-related fitness before applying the protocol. To standardize the sample and avoid cardiovascular risks due to the intensity of the effort, the Cafra test will be applied, which will enable the participant to perform the following tests. This test is used in the evaluation of physical education by the Education Quality Measurement System in the country. At the end of intervention aerobic capacity and resistance strength is going to be evaluated again.

The Cafra test goal is to determine the cardiovascular adaptive capacity of the participants from workloads of medium intensity during walking. If at the end of the test the individual has a heart rate equal to or greater than 160 beats per minute, he should not take the Navette test.

The Navette test is a cardiorespiratory fitness test. The moment in which the individual interrupts the test indicates the cardiorespiratory endurance. In addition, at the time this test is performed, blood pressure will be measured before and at the end, to rule out the presence of baseline or exercise-induced hypertension.

The heart rate will be measured with a heart rate sensor, which indicates in real time the heart rate reached, during the initial and final evaluations and during training sessions.

To evaluate muscular endurance, the abdominal test will be performed in 60 seconds and the largest possible number of push-ups without rest will be carried out. In this way, there will be a record of how the physical condition is before and after applying the protocol.

Adherence to physical training and nutritional consultations will be monitored through the online connection.

Physical training The training is going to have 2 phases, the initial phase and improvement phase, which are going to be differentiated according to work intensity following the recommendations of the American College of Sports Medicine. To prescribe the intensity of exercise karvonen formula is going to be used for which resting heart rate measured for a week is needed.

The methodology of work is going to be High intensity interval training (HIIT) using cardiovascular and endurance exercises using the own weight considering an intensity of 60-75% of the VO2max during the first 4 weeks (initial phase). The frequency of the training is 3 times a week under researcher online supervision between 3 to 7 pm Monday to Friday. During the improvement phase the intensity is going to increase to a 75-85% of the VO2max for 8 week. The intensity and effects of the training will be monitored thought heart rate sensors and the Borg Rating of Perceived Exertion Scale. Post-exercise monitoring, class coordination, reminders and motivation to participate will be performed by online group administered by the researchers.

Two physical education teachers will supervise each session.

Strategies to avoid acute changes in glycemia during training

It will be required that participants check the blood glucose by fingerstick before meals, before and after exercise, at bedtime, and twice a week around midnight.

The amount and type of food are not going to be controlled, but will be asked participants not exercising before or within 90 minutes after a meal . Considering that HIIT is associated to stable glycaemia no changes will be prescribed in fast-acting insulin dose.

For the management of blood glucose levels during the training period (before, during and after each session), a protocol based on the recommendations of the consensus for glycemia management during exercise using continuous glucose monitoring will be used.

Before starting and after completing each training session, a capillary blood glucose measurement will be requested as a safety measure and also in the event of symptoms of hypoglycemia or if the sensor shows or anticipates hypoglycemia.

In addition, when participants first start exercising, according to the midnight glycemia, it may be necessary to reduce the basal insulin dose by 20-50% on the day of exercise.

Participants using an insulin pump will use the same protocol, with a reduction in bolus doses and use of temporary basal on the days of exercise.

Mood evaluation The Patient Health Questionnaire 9 (PHQ-9) will be applied in its version for adolescents, which consists of nine questions designed to evaluate depressive symptoms according to DSM-5 criteria, on an ordinal scale according to the frequency of symptoms (never, some days, more than half of the days, almost every day). The score range is from 0 to 27 points, where higher values indicate a greater probability of a Depressive Episode. This scale is graded into 4 categories: 0-4 (minimal), 5-9 (mild), 10-14 (moderate), 15-19 (moderate to severe), 20-27 (severe). According to recent evidence, a score greater than or equal to 11 is recommended as a cut-off point to determine probable depressive episode in the Chilean population of adolescents. Patients who present a cut-off point higher than this in the initial evaluation will be excluded from protocol and will be referred to child psychiatry care.

To evaluate the effects of exercise on the depressed mood of adolescents, this survey will also be applied at the end of the intervention and 3 months after the intervention.

Blood Pressure Measurement In addition, during the initial evaluation, blood pressure will be measured before and after the physical tests to detect children with suspected hypertension, who as detailed above will be excluded from the intervention.

The BP recording will be carried out with an oscillometric device and the conditions for this procedure are: the adolescent must be seated, with the right arm uncovered, feet resting on the floor, and the BP cuff at the level of the heart. Before measuring the blood pressure the individual will need to remain sitting for at least five minutes. The blood pressure value will be evaluated according to the recommendations for the diagnosis of hypertension in children and adolescents of the American Academy of Pediatrics.

Statistical Analysis The initial analysis will examine data distribution through the Shapiro-Wilk test and baseline characteristics of all adolescents.

The quantitative variables will be expressed as means or medians, accompanied by deviation or interquartile ranges according to the exploration of normality. It will be analyzed each time of evaluation (transversal) using the chi-square test for categorical variables and the Student-t or Wilcoxon tests for continuous variables.

Relevant tests will be used to consider the non-dependence of the data obtained for both qualitative and quantitative analysis.

The effects of the treatment will be expressed , using mixed regression models (longitudinal) adjusting for potential confounders at baseline.

Subgroup analysis will be performed with interaction tests for relevant variables as BMI and socioeconomic status. Two separate definitions of compliance will be used. First, adolescents will be considered compliant to the HIIT treatment if participation is at least 75% of the number of training. Second, adolescents will be considered compliant to the HIIT if attendance is 100% of the counseling sessions to the nutritional and to endocrine consultations.

Outcome comparisons in the time will be analyzed intention-to-treat basis, regardless of whether is abandoned the study or fully adhere to the intervention. A secondary per-protocol analysis will be performed for the primary outcome including only the adolescents who were compliant with the protocol.

All analyses will follow a pre-specified statistical analysis plan. Stata v.14 software (StataCorp, College Station, TX) will be used for statistical analysis.

The eligibility criteria will be applied to the group of patients treated at Las Higueras Hospital and Guillermo Grant Benavente Hospital

Inclusion Criteria:

• Adolescents with type 1 diabetes
• Ages: 12-19 years (and in pubertal stage of at least Tanner stage III breast or genitalia)
• HbA1c between 7 and 11.5%
• Total daily insulin dose ≥0.7 units/kg/day.
• Both genders
• Patients treated regularly at Las Higueras Hospital and Guillermo Grant Benavente Hospital.

Exclusion Criteria:

• < 1 year of diabetes
• Any medical, mental or physical disability that contraindicates exercise.
• Practice of regular, structured and planned physical exercise outside the project, more than 2 times a week.
• Pregnancy or breastfeeding
• > 1 episode of severe hypoglycemia in the last 6 months

Eligibility criteria:

If the patient meets the inclusion criteria and does not present exclusion criteria, he/she may proceed to carry out physical evaluations to determine if has the conditions to perform the intervention. The patient may be ineligible for investigation in case of:

• Upon completing the Cafra test, His/her heart rate is> or equal to 160 (20, 23)
• If he/she shows blood pressure compatible with arterial hypertension before or after the initial physical evaluation.

Definition of arterial hypertension according to the recommendations of the American Academy of Pediatrics (30):

Blood pressure> or equal to the 95th percentile or> 130/80 mm Hg in adolescents greater than or equal to 13 years.

• If he/she develops any signs of post-exercise musculoskeletal injury (functional impotence, pain or swelling joint)
• In case they present a score ≥11 in the PHQ-9 questionnaire without mental health evaluation.