Effectiveness of Plyometric and Resistance Training in Young Adolescent Athletes - The 5th Congress of Exercise and Sport Sciences

Background: In adults, the rate of neural activation is a major factor in determining the rate of torque development, while the latter is a central determinant of jump performance. This relationship is unclear in youths. Further, the effects of resistance and plyometric training have been widely used and studied among adults, but much less so in children.

Aims: a) To examine the relationships between neuromuscular activation, maximal and explosive strength, and jump performance; b) To compare the effects of 8-week free-weight resistance (RT) and plyometric (PLYO) training, on muscle hypertrophy, maximal and explosive strength, associated electromyographic variables, as well as on squat-jump performance in young male athletes.

Methods: Forty-one 11‒13-year-old soccer players were divided into three groups: RT, PLYO, and control (CON). All participants completed isometric and dynamic (240°/s) knee extensions pre- and post-training. The association between peak torque (pT), peak rate of torque development (pRTD), jump performance, and neuromuscular activation was examined pre-training. The change in pT, pRTD, rate of muscle activation (Ra), m. vastus-lateralis thickness (VL_T), and squat-jump height was compared between groups.

Results: Isometric pT and pRTD were strongly correlated (r=0.71), but not related to jump height. Dynamic pT and pRTD, normalized to body mass, were significantly related to jump height (r=0.38‒0.66, p0.05). Normalized, but not absolute dynamic pRTD was significantly related to Ra (r=0.35, p0.05). No such relationship was observed in isometric contractions. Training resulted in significant (p0.05) increases in isometric pT (23.4 vs. 15.8%) and pRTD (15.0 vs. 17.6%), in RT and PLYO, respectively. Training significantly improved dynamic pT (12.4 and 10.8% in RT and PLYO, respectively), but not dynamic pRTD. Jump height increased in both training groups (RT=10.0%, PLYO=16.2%), but only PLYO was significantly different from CON. VL_T significantly increased in both RT (6.7%) and PLYO (8.1%). Ra increased in both groups (22 vs 44% in RT and PLYO, respectively), but this increase was not statistically significant.

Conclusion: In young athletes, neuromuscular activation and rate of torque development in dynamic contractions are related to jump performance, while, contrary to the case in adults, isometric contractions are not. Eight-week resistance or plyometric training, in addition to regular soccer training, improves strength and jump performance in young adolescent soccer players. Improvements following both training types were facilitated by neuromuscular changes as well as muscular hypertrophy. The findings have implications for the choice of training and assessment methods for young athletes. Gains in general strength (pT and pRTD), even in high-velocity, dynamic contractions, are best attained via resistance training. Plyometric training, shown most effective in improving jump performance, can be expected to also be superior in improving contractile explosiveness in other activities (e.g., sprinting), where contractions are immediately preceded by musculo-tendinous stretching (i.e., involving the stretch reflex).

Bareket Falk

Brock University

Bareket Falk is a pediatric exercise physiologist, with a wide interest in children’s responses to exercise and the physiological effects that physical training may have on children. She has published extensively in various areas in pediatric exercise physiology, including thermoregulation, metabolism and the effects of physical activity and training on growing bone and on muscle function. Her current work focuses on the effect of growth, maturation and physical activity on neuromuscular function. Bareket is a professor in the Department of Kinesiology at Brock University, Canada. She is the outgoing Editor-in-Chief of the journal Pediatric Exercise Science. Bareket is the mother of 3 boys, all of whom have inspired her research.