# Effects of 6-Weeks High-Intensity Interval Training in Schoolchildren with Insulin Resistance: Influence of Biological Maturation on Metabolic, Body Composition, Cardiovascular and Performance Non-responses PMID: 28706490 Journal: Frontiers in physiology Published: 2017 Authors: Alvarez C, Ramírez-Campillo R, Ramírez-Vélez R, Izquierdo M ## Question Do early and normal biological maturation groups differ in effects and non-responder prevalence for insulin resistance, body composition, cardiovascular, and performance outcomes after 6 weeks of school-based cycling HIIT? ## Summary This randomized school-based intervention studied 29 sedentary insulin-resistant children classified as early or normal maturation after a 6-week cycling HIIT program. Both maturation groups improved fasting insulin, HOMA-IR, and skinfold measures, while non-responder prevalence for the metabolic outcomes did not differ between maturation groups. The protocol used 18 closely monitored cycling sessions with progressive interval duration and number. ## Population - Sedentary insulin-resistant schoolchildren aged 8-13 years, grouped by early versus normal biological maturation. - Sample size: 29 - Age: Overall 11.4 +/- 1.7 years; HIIT-EM 11.0 +/- 1.0 years and HIIT-NM 12.0 +/- 1.0 years. - Sex: Reported inconsistently: Table 1 lists HIIT-EM 7 girls/4 boys and HIIT-NM 9 girls/8 boys, while Table 4 lists HIIT-EM 9 girls/3 boys and HIIT-NM 11 girls/6 boys. - Fitness level: Physically inactive, no regular HIIT background; participated in normal physical education. - Health status: Insulin resistance by HOMA-IR, fasting insulin, or fasting glucose; overweight/obesity range mean BMI. ## Methodology - Randomized intervention comparing early-maturation and normal-maturation HIIT groups, with pre/post outcomes and responder/non-responder classification by typical error. - 6 weeks of HIIT after familiarization and baseline assessment. - School/community field setting in Chile with afternoon sessions monitored by exercise physiologists. - Randomized study design. ## Protocol - 6-week supervised cycling HIIT. - Modality: Child-adapted cycle ergometer. - Work intervals: 40 seconds weeks 1-2, 50 seconds weeks 3-5, 60 seconds week 6. - Recovery: 120 seconds passive rest on the bicycle without movement. - Sets or repetitions: 8 intervals weeks 1-2, 10 intervals weeks 3-4, 12 intervals weeks 5-6. - Intensity: Modified Borg 1-10 RPE of 8-10; described as 70-100% maximum heart rate; cadence 50-70 rpm and speed 20-40 km/h. - Session duration: 23.3 to 40.0 minutes depending on week. - Frequency: 3 sessions per week. - Program length: 6 weeks. - Progression: Interval duration and interval count increased across weeks; ergometer load adjusted about every 2 weeks to maintain RPE 8-10. - Same HIIT protocol in normal maturation group. - Modality: Child-adapted cycle ergometer. - Work intervals: Same as intervention. - Recovery: Same as intervention. - Sets or repetitions: Same as intervention. - Intensity: Same RPE and estimated heart-rate target. - Session duration: Same as intervention. - Frequency: 3 sessions per week. - Program length: 6 weeks. - Progression: Same as intervention; comparison was maturation status rather than protocol dose. ## Outcomes ### Metabolic response non-responder prevalence Status: no clear change There were no significant differences between early and normal maturation groups in non-responder prevalence for fasting glucose, fasting insulin, or HOMA-IR. FGL NRs 83.3% vs 94.1%, p=0.348; FINS NRs 33.3% vs 41.2%, p=0.668; HOMA-IR NRs 25.0% vs 35.3%, p=0.555. ### Fasting insulin and HOMA-IR Status: improved Both groups significantly decreased fasting insulin and HOMA-IR after 6 weeks. FINS decreased 22.8% in HIIT-EM and 22.7% in HIIT-NM; HOMA-IR decreased 22.9% in HIIT-EM and 15.8% in HIIT-NM, reported p<0.05. ### Fasting glucose Status: no clear change Fasting glucose did not significantly change in either maturation group. Reported as no significant changes. ### Skinfold measures Status: improved Both groups significantly decreased tricipital, suprailiac, and abdominal skinfolds; no non-responders were observed for tricipital or abdominal skinfold. TSF -10.3% vs -6.8%; SSF -16.0% vs -18.9%; AbdSF -22.8% vs -15.9%; reported p<0.05 for significant decreases. ### Systolic blood pressure Status: mixed HIIT-EM significantly decreased systolic blood pressure, while HIIT-NM did not; non-responder prevalence differed between groups. SBP -11.9% in HIIT-EM versus -2.8% in HIIT-NM; SBP NRs 41.6% vs 70.5%. ### Strength Status: mixed HIIT-NM significantly improved 1RM leg extension and upper row; HIIT-EM changes were not significant. HIIT-NM 1RMLE +42.1% and 1RMUR +25.0%, both p<0.001. ### Safety and tolerability Status: no clear change All subjects had good exercise tolerance and no participant reported an injury. ## Practical Insights - A short 6-week progressive cycling HIIT program can improve insulin-resistance markers and skinfolds in supervised sedentary children with insulin resistance. - Individual response should be expected; mean improvement in insulin and HOMA-IR coexisted with substantial non-responder prevalence for fasting glucose and some other variables. - For youth or clinical-risk programming, supervision, familiarization, and attendance monitoring are key context, not optional details. ## Limitations - No non-exercise control group. - Small analyzed sample. - Special pediatric insulin-resistant population. - Additional exercise after training sessions was not controlled. - Attendance-based exclusion may limit generalizability. - Sex distribution differs between reported tables. ## Safety And Adherence - All subjects had good exercise tolerance. - None of the participants reported an injury. - Sessions were closely monitored by exercise physiologists. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/28706490/) (pubmed) - [DOI](https://doi.org/10.3389/fphys.2017.00444) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5489677/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.