Purpose: To compare the effects of plyometric drop jump training against those induced by regular soccer training, and to assess the transference effect coefficient (TEC) of drop-jumps (“trained exercises”) performed from 20- [DJ20] and 40-cm [DJ40] height boxes with respect to different physical qualities (jumping; linear and change of direction speed; kicking; endurance; maximal strength) in youth male soccer players. Methods: Participants were randomly divided into a control group (n=20; age: 13.5±1.9 years) and a drop jump (DJ) training group (n=19; age: 13.2±1.8 years); and trained for 7 weeks. To calculate the TEC between DJ20-DJ40 and the physical tests, the ratio between the “result gain” (effect-size [ES]) in the analyzed physical qualities and the result gain in the trained exercises were calculated. The TECs were only calculated for variables presenting an ES ≥0.2. Results: Significant improvements (ES=0.21-0.46; P < 0.05) were observed in the DJ training group, except in linear sprint performance. The control group improved only maximal strength (ES=0.28). Significant differences were observed in all variables (ES=0.20-0.55; P < 0.05) in favor of the DJ training group, except for maximal strength. Greater TECs were observed for DJ40 (0.58-1.28) than DJ20 (0.55-1.21). Conclusion: Our data suggest that youth players can improve their physical performance through the use of drop jumps. This is the first study that used the TEC to demonstrate the carry-over effect of plyometric training using drop jumps on physical performance of young soccer players.
- explosive strength