Effects of Two Plyometric Protocols at Different Surfaces on Mechanical Properties of Achilles Tendon in Children

The purpose of this study was to compare the changes in muscle strength and Achilles tendon strain after two plyometric training programs performed on different surfaces in children.
Thirty six children (21 girls, 15 boys) aged 9.30 ± 0.55 years were assigned into a mini-trampoline plyometric group (TPLG), a ground-plyometric group (GPLG) and a control group (CG). The training groups completed a 4-week plyometric intervention (PL) (three-times a week), consisting of hopping exercises performed either on a mini-trampoline (TPLG) or ground (GPLG). Achilles tendon strain, peak ankle plantar flexion torque (PAT), and rate of torque development (RTD) at 3 different angular positions of the ankle (15°, 0° and -15°) were measured before and after training.
The main finding of this study was that Achilles tendon strain decreased significantly after plyometric training performed on a mini-trampoline or ground surface ( 25% and 15%, for the TPLG and GPLG, respectively (P Both protocols show similar adaptations regardless of the surface of training. Training on elastic surface should be incorporated into exercise programs aiming either to enhance strength performance safely, or to achieve the target goal which is not only the safe performance but also the muscle-tendon system efficiency.