RESUMO
BACKGROUND: Paediatric obesity significantly increases the risk of developing cardiometabolic diseases across the lifespan. Increasing cardiorespiratory fitness (CRF) could mitigate this risk. High-intensity interval training (HIIT) improves CRF in clinical adult populations but the evidence in paediatric obesity is inconsistent. OBJECTIVES: The objectives of this study were to determine the efficacy of a 12-week, HIIT intervention for increasing CRF and reducing adiposity in children with obesity. METHODS: Children with obesity (n = 99, 7-16 years old) were randomised into a 12-week intervention as follows: (1) HIIT [n = 33, 4 × 4-min bouts at 85-95% maximum heart rate (HRmax), interspersed with 3 min of active recovery at 50-70% HRmax, 3 times/week] and nutrition advice; (2) moderate-intensity continuous training (MICT) [n = 32, 44 min at 60-70% HRmax, 3 times/week] and nutrition advice; and (3) nutrition advice only (nutrition) [n = 34]. CRF was quantified through a maximal exercise test ([Formula: see text]) while adiposity was assessed using magnetic resonance imaging (MRI), dual-energy X-ray absorptiometry (DXA) and air-displacement plethysmography. RESULTS: HIIT stimulated significant increases in relative [Formula: see text] compared with MICT (+3.6 mL/kg/min, 95% CI 1.1-6.0, P = 0.004) and the nutrition intervention (+5.4 mL/kg/min, 95% CI 2.9-7.9, P = 0.001). However, the intervention had no significant effect on visceral and subcutaneous adipose tissue, whole body composition or cardiometabolic biomarkers (P > 0.05). CONCLUSION: A 12-week, HIIT intervention was highly effective in increasing cardiorespiratory fitness when compared with MICT and nutrition interventions. While there were no concomitant reductions in adiposity or blood biomarkers, the cardiometabolic health benefit conferred through increased CRF should be noted. CLINICAL TRIALS REGISTRATION NUMBER: Clinicaltrials.gov; NCT01991106.