The effect of high-intensity progressive resistance training on adiposity in children: a randomized controlled trial.

BACKGROUND: High-intensity progressive resistance training (PRT) improves adiposity and metabolic risk in adults, but has not been investigated in children within a randomized controlled trial (RCT). OBJECTIVE: We hypothesized that high-intensity PRT (8 weeks, twice a week) would decrease central adiposity in children, as assessed via waist circumference. METHODS DESIGN/SETTING/PARTICIPANTS: Concealed randomization stratified by age and gender was used to allocate rural New Zealand school students to the wait-list control or PRT group. INTERVENTION: Participants were prescribed two sets (eight repetitions per set) of 11 exercises targeting all the major muscle groups at high intensity. PRIMARY OUTCOME: Waist circumference; secondary outcomes included whole body fat, muscular fitness (one repetition maximum), cardiorespiratory fitness (peak oxygen consumption during a treadmill test), lipids, insulin sensitivity and fasting glucose. RESULTS: Of the 78 children (32 girls and 46 boys; mean age 12.2(1.3) years), 51% were either overweight (33%) or obese (18%). High-intensity PRT significantly improved waist circumference (mean change PRT -0.8 (2.2) cm vs +0.5 (1.7) cm control; F=7.59, P=0.008), fat mass (mean change PRT +0.2 (1.4) kg vs +1.0 (1.2) kg control; F=6.00, P=0.017), percent body fat (mean change PRT -0.3 (1.8)% vs +1.2 (2.1)% control; F=9.04, P=0.004), body mass index (mean change PRT -0.01 (0.8) kg m(-2) vs +0.4 (0.7) kg m(-2) control; F=6.02, P=0.017), upper body strength (mean change PRT+11.6(6.1) kg vs +2.9(3.7) kg control; F=48.6, P<0.001) and lower body strength (mean change PRT +42.9(26.6) kg vs +28.5(26.6) kg control; F=4.72, P=0.034) compared to the control group. Waist circumference decreased the most in those with the greatest baseline relative strength (r=-0.257, P=0.036), and greatest relative (r=-0.400, P=0.001) and absolute (r=0.340, P=0.006) strength gains during the intervention. CONCLUSION: Isolated high-intensity PRT significantly improves central and whole body adiposity in association with muscle strength in normal-weight and overweight children. The clinical relevance and sustainability of these changes in adiposity should be addressed in future long-term studies.

Effects of resistance training on metabolic fitness in children and adolescents: a systematic review.

The majority of resistance training (RT) research with children to date has focused on pre-adolescents and the safety and efficacy of this type of training rather than the potential metabolic health benefits. Our objectives, using computerized databases, were (i) to systematically review studies utilizing RT interventions with children and adolescents <18 years; (ii) to investigate the metabolic health outcomes (adiposity, lipids, insulin, glucose) associated with RT; (iii) to provide recommendations for future investigations. A total of 12 studies met the review criteria. There is only a small amount of evidence that children and adolescents may derive metabolic health-related adaptations from supervised RT. However, methodological limitations within the body of this literature make it difficult to determine the optimal RT prescription for metabolic fitness in children and adolescents, and the extent and duration of such benefits. More robustly designed single modality randomized controlled trials utilizing standardized reporting and precise outcome assessments are required to determine the extent of health outcomes attributable solely to RT and to enable the development of evidence-based obesity prevention and treatment strategies in this cohort.