Trainability of Neuromuscular Power in Youth

The following is an exclusive excerpt from the book Developing Power, published by Human Kinetics. All text and images provided by Human Kinetics.

Research shows that traditional resistance training, ballistic exercises, plyometrics, and weightlifting are the most commonly used forms of resistance training to develop neuromuscular power (13). While literature examining the interaction between growth, maturation, and the trainability of neuromuscular power remains scarce, several studies show that both children and adolescents are able to increase this physical quality following exposure to appropriate resistance-based training interventions. Within the pediatric literature, research shows that traditional resistance training (52), plyometrics (47), weightlifting (11), explosive strength training (28), and combined training (83) are all safe and effective means of enhancing various indices of neuromuscular power. Resistance training has also been shown to increase insulin sensitivity in obese youth because the training mode can increase both the size and recruitment of fast-twitch muscle fibers (74).

Because there is little evidence of hypertrophic adaptations in children, resistance training–induced gains in neuromuscular power during childhood is likely determined by changes in the nervous system (5). Conversely, training-induced gains in neuromuscular power during adolescence typically reflect not only adaptations to the nervous system but also structural and architectural properties (53). More research is required to examine the specific mechanisms that mediate training-induced gains in neuromuscular power in youth, especially those that underpin long-term adaptations across different stages of maturation.

A fundamental relationship exists between muscular strength and neuromuscular power. Evidence shows that people with higher strength levels have a greater capacity to produce power (13). Given its multiple health and performance benefits and its ability to reduce the risk of injury, resistance training should form an integral part of any youth-based strength and conditioning program (40). Practitioners should ensure that all children and adolescents are provided with developmentally appropriate training strategies to develop sound movement mechanics while simultaneously increasing muscular strength levels (40). In combination, movement competency and muscular strength will serve as the foundations for a robust system through which high levels of muscular power can be produced and attenuated during whole-body dynamic activities. The emphasis on muscular strength and movement competency is especially prudent considering the negative trends in muscular strength levels and motor fitness of modern-day youth (12, 70). Because of the increased sedentariness of children (79) and the fact that children are less capable of maximally recruiting their high-threshold Type II motor units (18), it is highly probable that in most cases simply by focusing on increasing movement competency and muscular strength capacities, practitioners will be able to indirectly increase neuromuscular power.

Researchers have examined the effects of a 2-year resistance training program on strength performance in youth soccer players and have shown that the magnitude of strength gains increases with age (35). Long-term exposure to periodized resistance training resulted in relative strength levels being 0.7 × body weight in 11- 12-year-olds, 1.5 × body weight in 13- 15-year-olds, and 2.0 × body weight in 16- 19-year-olds (35). In a separate study, the same group of researchers showed that after 2 years of strength training, 13-, 15-, and 17-year-old soccer players simultaneously improved 1RM squat strength (100%-300%) and sprinting speed (3%-5%), which was used as a surrogate measure of power (71).

Not all youth wish to engage in competitive sports; therefore, practitioners should not base strength and power training prescription on data from homogenous populations (e.g., elite youth soccer players). Research has examined the effectiveness of integrative neuromuscular training interventions on the health- and skill-related measures of fitness in 7-year-old school-age children (21). The study showed that children were able to make significant gains in curl-up and push-up performance (increased muscular strength and endurance) and also long jump and single-leg hop performance (increased neuromuscular power) by following an 8-week, twice-weekly (15-min sessions) training program (21). A follow-up study showed that after an 8-week detraining period, training-induced gains in curl-up and single-leg hop performance (muscular strength and endurance) were maintained, while those for long jump performance (neuromuscular power) significantly decreased (22). This might suggest that muscular strength is easier to maintain in children, while neuromuscular power capacities require more frequent stimuli to prevent detraining.

Improvements in muscular power have also been shown in school-age youth who followed a 4-week plyometric training program (47). This study showed that 12- and 15-year-old boys were able to significantly improve SSC function, while 9-year-olds were also able to show improvements, albeit not significantly. This may highlight an age-dependent response to plyometric training and may indicate that younger children possibly require a different amount of training to elicit similar gains, such as those their more mature peers experience. Conversely, it could simply suggest that training-induced adaptation takes longer to materialize in younger children, which supports the notion of a long-term approach to training for athletic development in youth. Cumulatively, these studies show that both children and adolescents can make resistance training gains in neuromuscular power, that youth can make improvements in neuromuscular power as a result of increasing their muscular strength capacities, and that training-induced gains in neuromuscular power may diminish at a faster rate than muscular strength in youth.

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