Pearce, A. J., Grikepelis, L. A., & Kidgell, D. J. (2009). Neural adaptations following strength training in children and adolescents: A TMS pilot study. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

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"It has been suggested that when an individual participates in strength training, much of the initial increase in strength is attributed to adaptations (plasticity) in the central nervous system. It has been proposed that strength training is comprised of a form of motor skill learning, to explain short-term improvements in strength in children and adolescents." This preliminary study examined strength changes and central nervous system adaptations following a four-week training of the biceps brachii muscle in healthy children and adolescents (M = 5; F = 5) who were new to strength training. Ss completed 12 strength training sessions (two sets, increased to three sets of 15 repetitions at individualized prescribed weights) over four weeks. Pre- and post-training testing consisted of biceps brachii maximal voluntary contraction strength (via hand-held dynamometry) and sub-maximal strength (10 RM test); relaxed and flexed upper arm girths; and motor evoked potential excitability using single–pulse transcranial magnetic stimulation.

Significant improvements in both arms were shown post-training for maximal voluntary contraction and the 10-repetition sub-maximal strength test. No changes were recorded in group mean upper arm girths in either arms for the relaxed and flexed conditions. Group mean corticomotor excitability projecting from the motor cortex to the biceps brachii showed significant post-training increases. Mean motor evoked potential excitability amplitudes projecting from the motor cortex to the right arm increased from ~1.7 to ~2.4 mV and to the left arm from ~1.2 to ~1.6 mV.

Implication. Rapid strength increases and central nervous system changes that may account for those rapid increases in strength occur without associated muscle hypertrophy. [Training over four weeks can be explained better as improvements in skill in performing the exercises without any structural or physiological change in the muscles. Strength gains in novice individuals are attributable to developing the skill of using existing structural resources.]

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