Jumps & Plyometric Training

Imagine jumping down from a box, rebounding as quickly and explosively as possible upon ground contact, and landing on the next box. Now imagine that, at precisely the same time, your motor cortex is stimulated with a strong magnetic pulse using transcranial magnetic stimulation (TMS). If this brain stimulation is timed just before your feet touch the ground, you suddenly lose the ability to rebound – no matter how hard you try. The motor command that normally drives this explosive movement has effectively been disrupted. And this happens even in some of the most coordinated athletes around: x-game inline skaters who perform thousands of jumps and have exceptional control over their movements!

Some of the most interesting – and funniest – experiments in our lab, both for researchers and participants, have been conducted while investigating this type of movement, known as the stretch-shortening cycle (SSC). Our aim was to better understand the neural mechanisms underlying explosive jumping movements and, ultimately, to identify ways to optimize their training. In a series of experiments, we demonstrated the important contribution of spinal stretch reflexes to the rapid and powerful rebound following ground contact [1-3]. Using TMS, we also revealed the contribution of the primary motor cortex to the control of this complex movement [4, 5]. Interestingly, depending on the type of training and the height from which an athlete drops, different phases of ground contact can be specifically targeted: the early phase, which is strongly influenced by spinal reflex mechanisms, or the later phase, in which motor cortical activity plays a more prominent role [6, 7]. These findings provided important insights into how plyometric training can be designed to target specific neural mechanisms involved in explosive performance.

Before moving on to how best to train jumping and other stretch-shortening cycle movements, let me share another anecdote from our research. Together with a team from Copenhagen, we travelled to Aalborg to use a sophisticated robotic device capable of changing the floor height within the blink of an eye. We had just three days to complete the experiments. Unfortunately, it took us almost the entire three days to overcome the technical problems and get everything working. By Friday evening, the laboratory was finally ready for measurements – but all the students had already left campus. All the students? Well, not quite! Fortunately, there was a party going on nearby, so we recruited our participants directly from the party and ended up conducting the entire experiment throughout the night. Study successfully completed – and eventually published in The Journal of Physiology! [5].

To improve jump performance in the short-term, two approaches were shown to be particularly beneficial: an external focus of attention and augmented feedback  [8, 9]. Thereby, participants performed best when provided with augmented feedback about their jump height, followed by an external focus and a neutral or internal focus of attention. Sometimes, the combination of both external focus of attention and augmented feedback was even more effective [9].

We also investigated the effects of augmented feedback on long-term training adaptations. Here, we found that providing feedback after every jump (100% feedback frequency) resulted in greater improvements than providing feedback after only half of the jumps (50%) or providing no augmented feedback at all [10]. This finding challenges the widespread assumption derived from the so-called guidance hypothesis, which suggests that frequent feedback may create dependency and ultimately impair long-term learning and retention. While this hypothesis was originally developed based largely on relatively artificial laboratory tasks, our findings suggest that its predictions do not necessarily apply to complex, real-world sports movements. In the context of explosive jumping, frequent and objective feedback can be a highly effective tool for optimizing training and improving performance.

^{1. Leukel, C., W. Taube, M. Gruber, M. Hodapp, and A. Gollhofer, Influence of falling height on the excitability of the soleus H-reflex during drop-jumps. Acta Physiol (Oxf), 2008. 192(4): p. 569-76.}

^{2. Leukel, C., A. Gollhofer, M. Keller, and W. Taube, Phase- and task-specific modulation of soleus H-reflexes during drop-jumps and landings. Exp Brain Res, 2008. 190(1): p. 71-9.}

^{3. Leukel, C., J. Lundbye-Jensen, M. Gruber, A.T. Zuur, A. Gollhofer, and W. Taube, Short-term pressure induced suppression of the short-latency response: a new methodology for investigating stretch reflexes. J Appl Physiol (1985), 2009. 107(4): p. 1051-8.}

^{4. Taube, W., C. Leukel, M. Schubert, M. Gruber, T. Rantalainen, and A. Gollhofer, Differential modulation of spinal and corticospinal excitability during drop jumps. J Neurophysiol, 2008. 99(3): p. 1243-52.}

^{5. Zuur, A.T., J. Lundbye-Jensen, C. Leukel, W. Taube, M.J. Grey, A. Gollhofer, J.B. Nielsen, and M. Gruber, Contribution of afferent feedback and descending drive to human hopping. Journal of Physiology-London, 2010. 588(5): p. 799-807.}

^{6. Taube, W., C. Leukel, B. Lauber, and A. Gollhofer, The drop height determines neuromuscular adaptations and changes in jump performance in stretch-shortening cycle training. Scandinavian Journal of Medicine & Science in Sports, 2012. 22(5): p. 671-683.}

^{7. Taube, W., C. Leukel, and A. Gollhofer, How neurons make us jump: the neural control of stretch-shortening cycle movements. Exerc Sport Sci Rev, 2012. 40(2): p. 106-15.}

^{8. Keller, M., B. Lauber, M. Gottschalk, and W. Taube, Enhanced jump performance when providing augmented feedback compared to an external or internal focus of attention. Journal of Sports Sciences, 2015. 33(10): p. 1067-1075.}

^{9. Wälchli, M., J. Ruffieux, Y. Bourquin, M. Keller, and W. Taube, Maximizing Performance: Augmented Feedback, Focus of Attention, and/or Reward? Medicine & Science in Sports & Exercise, 2016. 48(4): p. 714-719.}

^{10. Keller, M., B. Lauber, D. Gehring, C. Leukel, and W. Taube, Jump performance and augmented feedback: Immediate benefits and long-term tr}