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.
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).
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.
Parallel
HIIT plus plyometric training
BehavioralThe HIIT plus plyometric training will perform two weeks of exercise adaptation involving 25 minutes of MICT at 65% of maximal heart rate (HRmax) and 5 minutes of jumps in place at 5 - 6 of the EPinfant scale of Perceived exertion. The HIIT plus plyometric training will perform 15 minutes of HIIT and 5 minutes of jumps each session. The HIIT phase will be performed in a work recovery intensity at 85 and 50% of the HRmax. The work phase of jumps will be performed "all out," and the recovery phase will be performed at 5 - 6 of the EPinfant scale of perceived exertion. The work: recovery bouts will be progressed from 1:4 (15 seconds: 60 seconds) at weeks 3-6, to 1:3 (15 seconds: 45 seconds) at weeks 7-9, and to 1:3 (15 seconds: 30 seconds) at weeks 10-12. In all sessions, the rate of perceived exertion, heart rate, and exercise planning compliance will be measured.
HIIT
BehavioralThe HIIT group will perform two weeks of exercise adaptation involving 30 minutes of moderate-intensity continuous training (MICT) at 65% of the maximal heart rate (HRmax) reached in the maximal oxygen consumption test. The HIIT group will perform 20 minutes of HIIT each session, with a work: recovery intensity at 85% and 50% of HRmax, respectively. The work: recovery bouts will be progressed from 1:4 (15 seconds:60 seconds) at weeks 3-6, to 1:3 (15 seconds:45 seconds) at weeks 7-9, and to 1:2 (15 seconds: 30 seconds) at weeks 10-12. In all sessions, the rate of perceived exertion, heart rate, and exercise planning compliance will be measured.
Achilles Tendon Stiffnes (N/mm)
The stiffness will be estimated as the slope of the linear tendon elongation-force relationship above 50% of each participant's maximum attained force.
Achilles Tendon Young Modulus
The Achilles tendon young modulus will be estimated as the slope of the linear tendon stress-strain relationship above 50% of each participant's maximum attained force.
Achilles Tendon Force (N)
The Achilles tendon force of the Achilles tendon will be calculated as the plantar flexors torque divided by the Achilles tendon moment arm plus the dorsiflexor contribution.
Achilles Tendon Elongation (mm)
Tendon elongation will be measured as the Achilles tendon myotendinous junction displacement (ArtUS, Telemed, Vilnius, Lithuania) from rest in the MIVC trials. The tendon lengthening will be normalized by the Achilles tendon moment arm.
Achilles Tendon Stress (MPa)
The tendon stress will be calculated as the ratio between the mean maximum attained force and the smallest cross-sectional area measured for each participant.
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