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.