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

Abstract

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 À0.8 (2.2) cm vs þ 0.5 (1.7) cm control; F ¼ 7.59, P ¼ 0.008), fat mass (mean change PRT þ 0.2 (1.4) kg vs þ 1.0 (1.2) kg control; F ¼ 6.00, P ¼ 0.017), percent body fat (mean change PRT -0.3 (1.8)% vs þ 1.2 (2.1)% control; F ¼ 9.04, P ¼ 0.004), body mass index (mean change PRT À0.01 (0.8) kg m À2 vs þ 0.4 (0.7) kg m À2 control; F ¼ 6.02, P ¼ 0.017), upper body strength (mean change PRT þ 11.6(6.1) kg vs þ 2.9(3.7) kg control; F ¼ 48.6, Po0.001) and lower body strength (mean change PRT þ 42.9(26.6) kg vs þ 28.5(26.6) kg control; F ¼ 4.72, P ¼ 0.034) compared to the control group. Waist circumference decreased the most in those with the greatest baseline relative strength (r ¼ À0.257, P ¼ 0.036), and greatest relative (r ¼ À0.400, P ¼ 0.001) and absolute (r ¼ 0.340, P ¼ 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.

Strength Capacity and Cardiometabolic Risk Clustering in Adolescents

“…23,43 There is also evidence to support the efficacy of an isolated high-intensity strength training intervention (ie, without additional dietary intervention or aerobic exercise) to safely reduce adiposity among overweight children. 44 The current findings are supportive of this because both boys and girls with greater strength capacities had the lowest %BF and BMIs.…”

Exercise and Insulin Resistance in Youth: A Meta-Analysis

“…29 IR was calculated by using fasting levels of insulin and glucose by using the homeostasis model assessment (HOMA) technique in each study included in this analysis. 22,25,31,32,[34][35][36][37][38][39][40][41] A decrease in fasting insulin levels or IR among participants in exercise interventions resulted in a positive ES. Two authors (M.V.F.…”

Resistance Training in Youth - Benefits and Characteristics

“…Even though, there is some inherent risk for musculoskeletal injuries with RT, as with any other form of PA, this risk is no greater than that of many other recreational activities or sports youth generally participate in [19]. In fact, properly administered RT programs may actually reduce injury risk during various physical activities in children [20,50] while providing a variety of health benefits [20,21,[50][51][52]. Childhood and adolescence have been suggested as the opportune time to induce beneficial adaptations in bone development due to synergistic effects of mechanical stress induced by RT and growth-related increase in bone mass [27,43,46,47,[53][54][55].…”

“…Further, a clustering of chronic disease risk factors observed during childhood has been shown to persist into adulthood [105]. Particularly overweight and obese children have shown favorable changes in body composition and insulin sensitivity with RT, which was attributed to qualitative changes in skeletal muscle [24,52,74,106,107]. Further, the previously addressed beneficial adaptations in bone development could reduce the risk for osteoporosis and associated fractures later in life [108].…”