BRINGING SCIENCE TO TREATMENT
2019 Boca Juniors’ Fabiana Vallejos in action REUTERS/Agustin Marcarian TPX IMAGES OF THE DAY
Spring has sprung in the Northern Hemisphere while the mild days of fall are starting in the Southern. With the change in the weather, young athletes everywhere are getting out and playing footie. Meanwhile, coaches scrambling for best practices to give their team the edge often resort to technical training. Chilean researchers have just released a study that may have coaches rethinking all those cone drills.
These sports scientists wondered if plyometric jump training would enhance predictable measures of strength as well as carryover and improve other skills unrelated to the jumping exercise(1). To measure the effects of drop jump (DJ) training, they divided 39 male competitive youth soccer players into a control group (CG) and a DJ group. The average age of the subjects was 13.2 years. The study was conducted mid season so that all participants were currently playing at the same level.
The CG continued with their regularly scheduled training practices twice per week. The DJ group swapped their usual technical training for DJ training during their twice-weekly practice. The protocol consisted of three sets of 10 reps of 20-cm and 40-cm drop jumps for seven weeks. The athletes rested between reps for 15-seconds for the 20-cm jumps and 90-seconds for the 40-cm jumps. All jump sessions were monitored to ensure correct technique and athletes were encouraged to achieve their highest possible jump with the smallest possible amount of ground contact between the drop and the jump.
Various measurements of ability were conducted both before and after the intervention. They included:
The researchers found that the DJ group showed significant within-group improvement after the DJ training intervention in all areas measured except the 20-meter sprint. Within the CG, the post-testing revealed significant improvement in only the 5-rep max test after the 7 weeks, and a significant decrease in the 20-meter sprint and change of direction performances. When comparing the two groups post-intervention assessments, the improvements within the DJ group were significantly better than those of the CG with the exception of the 5-rep max in which there was no significant difference.
You may be wondering why these findings may be important to rehabilitation professionals. Despite the fact that this study was done on young athletes, it tells us something about the transference effect of certain exercises. A transference effect occurs when gains are made in an untrained exercise as a result of an unrelated exercise. An example of this is when strength gains are made in a contralateral limb despite never having exercised that side. In other words, will the explosive training and neuromuscular changes induced by drop jumps improve other measures of explosive movement? This study seems to support that it does. Therefore, while technical drills have their value, would rehabilitation time be better spent on activities such as the drop jump?
While all test subjects in this study were healthy young males, should physios consider activities with proven crossover benefits as part of the rehab course for injured athletes? Would the overall gains be greater and the time in rehab spent more efficiently? This study doesn’t answer those questions, but it leads us to consider the rehab activities we recommend and how well these activities train athletes to meet the benchmarks set for return-to-play readiness.
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