Effects and Mechanisms of Strength Training in Children

Abstract

It has been demonstrated that strength training can be organized in children in a safe and effective way. However, there is limited data regarding its impact on muscle hypertrophy. This study investigated the effects of a high-intensity strength training (HIS) on knee extensor/flexor strength, countermovement (CMJ) jumping height, postural control, soft lean mass and muscle cross-sectional area (CSA) of the dominant leg in prepubertal children. Thirty-two children participated in this study and were assigned to an intervention (INT; N=17) or a control class ( N=15). The INT participated in 10 weeks of weight-machine based HIS integrated in physical education. Pre/post tests included the measurements of peak torque of the knee extensors/flexors at 60 and 180°/s, CMJ jumping height, postural sway, soft lean mass of the leg by bioelectrical impedance analysis, and CSA (m. quadriceps) by magnetic resonance imaging. HIS resulted in significant increases in knee extensor/flexor peak torque (60°/s and 180°/s). HIS did not produce significant changes in CMJ jumping height, postural sway, soft lean mass, and CSA. Although HIS was effective at increasing peak torque of the knee extensors/flexors in children, it was unable to affect muscle size. It appears that neural factors rather than muscle hypertrophy account for the observed strength gains in children.

Muscle Hypertrophy in Prepubescent Tennis Players: A Segmentation MRI Study

“…Training-induced hypertrophy is the most likely mechanism to explain these findings. The effect of tennis on muscle size of the dominant arm observed in the present study is greater than the reported in healthy children using different strength training programs [1], [2], [3]. It is possible that the inclusion of plyometric movements in tennis strokes and not in the other studies [19], a higher training frequency in our TP (6 d/week) [6], together with a greater potential of the arms than the thighs for muscle hypertrophy [20], [21] may explain these differences.…”

“…There is discrepancy about training-induced muscle hypertrophy in preadolescents [1], [2], [3]. It has been suggested that inadequate levels of circulating androgens [3] or training stimulus [4] may limit muscle hypertrophy before puberty.…”

Effectiveness of Traditional Strength vs. Power Training on Muscle Strength, Power and Speed with Youth: A Systematic Review and Meta-Analysis

“… %Δ, Percent change from pre-test to post-test; BPT, balance training before plyometric training; BW, bodyweight; cm, centimeter; CMJ, counter movement jump; CSTS, core strength training on stable surface; CSTU, core strength training on unstable surface; EE, elbow extension; EF, elbow flexor; ET, elastic tubing; Ex, exercises; FFM, fat free mass; Freq, frequency; FW, free weight; Int, intensity; Isok, isokinetic; Isom, isometric; Isot, isotonic; KE, knee extension; KF, knee flexion; kg, kilogram; m, meter; Med, Medicine; Mod, moderate; MVIC, maximal voluntary isometric contraction; N, number of participants; PBT, plyometric training before balance training; PE, physical education students; PHV, peak height velocity; Post, post-test; Power, power measures; Pre, pre-test; PT, peak torque; Reps, repetitions; RM, repetition maximum; RPE, rating of perceived exertion; s, second; SD, standard deviation; Strength, strength measures; T, trained youth; TMS, trunk muscle strength; Tr, training status; U, untrained youth; Var, varied; Wks, weeks . Additional Citations for Table 2A are found in the text reference list (Hettinger, 1958; Funato et al, 1986; Sewall and Micheli, 1986; Weltman et al, 1986; Blimkie, 1989; Ozmun et al, 1994; DeRenne et al, 1996; Gorostiaga et al, 1999; Sadres et al, 2001; Flanagan et al, 2002; Pikosky et al, 2002; Tsolakis et al, 2004; Drinkwater et al, 2005; Benson et al, 2007; Faigenbaum et al, 2007a, 2014, 2015; Channell and Barfield, 2008; Rhea et al, 2008; Teng et al, 2008; Chelly et al, 2009; Dorgo et al, 2009; Lubans et al, 2010; Velez et al, 2010; Wong et al, 2010; Ebada, 2011; Granacher et al, 2011a,b, 2014, 2015; Ignjatovic et al, 2011; Muehlbauer et al, 2012; Santos and Janeira, 2012; Moore et al, 2013; Moraes et al, 2013; Sander et al, 2013; Coskun and Sahin, 2014; Ferrete et al, 2014; Pesta et al, 2014; Piazza et al, 2014; Dalamitros et al, 2015; Gonzalez-Badillo et al, 2015; dos Santos Cunha et al, 2015; Sarabia et al, 2015; Tran et al, 2015; Eather et al, 2016; Harries et al, 2016; Lloyd et al, 2016; Negra et al, 2016; Prieske et al, 2016; Rodriguez-Rosell et al, …”

Position statement on youth resistance training: the 2014 International Consensus

“…During this period, sex differences in muscular strength begin to emerge, with boys demonstrating accelerated gains as a result of the adolescent spurt, and girls appearing to continue to develop in a more linear fashion 3. Potential factors inherently responsible for increases in strength during childhood appear to be related to the maturation of the central nervous system,47 for example, improvements in motor unit recruitment, firing frequency, synchronisation and neural myelination 48 49. Strength gains during adolescence are typically driven by further neural development, but structural and architectural changes resulting largely from increased hormonal concentrations, including testosterone, growth hormone and insulin-like growth factor play a significant role, especially in males 2.…”