Effects of HIIT and Concurrent HITT/Plyometric Training on Muscle-tendon Structure, Function and Metabolism in Pediatric Population with Obesity At Different Biological Maturation States (HIIT-PRO Kids).

The randomized controlled trial will compare the effects of a High-intensity interval training (HIIT) protocol versus a HIIT plus plyometric training in the muscle-tendon structure function and metabolism of the pediatric population with obesity at different biological maturational stages (pre-to-age peak velocity \[APHV\] and post-APHV). Both groups perform baseline evaluations of the main and secondary outcomes and receive the intervention for twelve weeks, three times per week. Once the interventions are completed, the participants undergo the same evaluations they performed at baseline.

The prevalence of pediatric obesity increased 4.2-fold between 1976 and 2022, and it's expected to continue increasing toward 2030. Pediatric obesity is a public health problem due to its multiple metabolic comorbidities. Moreover, body weight and fat infiltration due to pediatric obesity negatively affect muscle-tendon structure, function, and metabolism, negatively impacting physical activity levels, active play, functional performance (e.g., jumping capacity), and quality of life. As a solution, HIIT protocols could decrease body weight and fat percentage and increase muscle oxidative capacity. The addition of plyometric training to HIIT protocols could generate the same effects as the HIIT protocol alone, with an additional enhancement in functional performance. However, the influence of biological maturation stages in the adaptations to training in pediatric population with obesity has been scarcely reported. Thus, throughout different biological maturation stages, such as pre-to-age peak velocity (APHV) (early stage of biological maturation) to post-APHV (final stage of biological maturation stage), an increase in testosterone, growth factors, and glycolytic metabolism capacity occurs. Therefore, the differences in the anabolic milieu and glycolytic metabolism between the pre-APHV and post-APHV could produce a differential capacity of training stimuli to modify the muscle-tendon, structure, function, and metabolism in these pediatric population with obesity. Therefore, this study aims to determine the effects of HIIT and concurrent HIIT and plyometric training in the muscle-tendon structure, function, and metabolism of the pediatric population with obesity in different maturation stages.

The study will be a parallel-group randomized controlled trial that compares the effects of HIIT versus HIIT plus plyometric training on muscle-tendon structure, function, and metabolism in the pediatric population pre-APHV and post-APHV with obesity in a public health setting. The primary outcome will be the Achilles tendon mechanical properties. We estimate a sample size of 10 participants per group and 40 in total.

The investigators aim to demonstrate the beneficial effects of HIIT plus plyometric training on the muscle-tendon structure and metabolism of the pediatric obesity population. Moreover, the researchers expected a difference in the adaptations provided by the training protocol between the pre-APHV and post-APHV groups.

Eligibility Criteria:
Inclusion Criteria:

* Pediatric population with obesity determined by the body mass index by z-score (BMI-z) ≥ 2 standard deviations (SD) and ≤ 3.5 SD of the median for age and sex.
* Pediatric population with -1 to -3 APHV (pre-APHV) and +1 to +3 APHV (post-APHV).

Exclusion Criteria:

* Cognitive Disabilities.
* Musculoskeletal condition that prevents regular physical activity.
* Severe heart diseases that contraindicate the practice of physical activity.
* Individuals who perform supervised exercise in the past six months.