We would like to comment on the paper by Dotan et al. (8) entitled “Child-adult differences in muscle activation—a review.” Dotan et al.’s review (8) in conjunction with the commentary of O’Brien et al. (20) constitutes an important contribution to the question “who are stronger: children or adults?” based on specific force comparisons between children and adults and not on absolute values. For simplification reasons, we would like to limit the context of this question to single-joint isometric and isokinetic contractions only. Hence, we will not discuss multi-joint dynamic actions.
Eleni Bassa, Dimitrios Patikas, Konstantinos Hatzikotoulas and Christos Kotzamanidis
Savvas N. Lazaridis, Eleni I. Bassa, Dimitrios Patikas, Konstantinos Hatzikotoulas, Filippos K. Lazaridis and Christos M. Kotzamanidis
This study examines the biomechanical differences during different vertical jump tasks in 12 prepubescent and 12 adult males. The sagittal knee kinematics, vertical ground reaction force (vGRF) and electromyographic (EMG) activity of 5 lower extremity muscles were recorded. Compared with boys, men presented higher peak vGRF during the propulsive phase in all examined jumps, but lower values during the braking phase, even when related to body mass. Normalized EMG agonist activity in all phases was higher in men (p < .05), while antagonist coactivation was enhanced in boys (p < .05). The knee joint was on average 9 degrees more flexed at touchdown in men during drop jump tasks, but boys exhibited 12 degrees and 17 degrees higher knee flexion at the deepest point when performing drop jump from 20 and 40 cm, respectively. In conclusion, the performance deficit observed in boys in all jump types is a reflection of their immature technique, which could be partly attributed to the less efficient stiffness regulation and activation of their neuromuscular system.