The power of instructions in jumping
As strength coaches we focus a lot on exercise selection. But exercise execution is just as critical: perform the same exercise differently and you can train two entirely different physical qualities. On last month’s GAINcast with Professor Warren Young we got one great example: how you intrust an athlete to perform a drop jump can lead to drastically different execution.
The search for the right stimulus
Depth or drop jumping involves jumping vertically immediately after landing from a fall or drop from a predetermined height. As Nick Lumley wrote about on this site, some people use the terms depth and drop jump interchangeable, while others use the different terms to distinguish between the weight of the fall. Most people focus on the fall height as the main differentiating factor in the jump because as height increases, so does ground contact time and joint angles, leading to a transition from training the fast stretch shortening cycle to training the slow stretch shortening cycle. This is true, but it is also only part of the picture.
As mentioned in the introduction, picking the exercise (and associated height) is only part of the equation. Execution is also critical. Without explicit instructions on technique, the desired technique might not be used. And explicit feedback is also crucial. It can take the form of quick feedback on jump height or contact time from EZEJump from Swift Performance or similar contact mat. Simply prescribing a height for a jump might not be enough to ensure you are training what you think you are training.
Instructing the athlete
The power of how we instruct athletes was looked at by Young and his colleagues (including future international rugby coach John Pryor) in an interesting study in 1995 titled Effect of Instructions on Characteristics of Countermovement and Drop Jump Performance. In short, their research shows how large of an effect a some words and feedback can have. We assume a high fall will train the slow stretch shortening cycle, but when instructed differently it can train the fast cycle. And shallow fall, on the other hand, can also train the slow cycle. The instruction is critical.
In the study athletes were instructed to perform drop jumps with different instructions. On some attempts they instructed to attempt for maximal height. Other attempts they were told to achieve minimum ground contact time. And finally they were told to both maximize height while reducing ground contact time. Here are the results:
As you can see, when told to focus on jump height, shallow falls from 30cm had massive contact times of over 400ms. In fact, the biomechanics of these jumps (including angles and jump height) were nearly identical to a standing countermovement jump from the ground.
Higher falls from 60cm, on the other hand, saw impressively short contact times when athletes were instructed on contact time rather than height.
What do you want to train?
So what instruction is better? I can’t answer that. No instruction is inherently better than another. What is key is that the instruction should match the training stimulus you are chasing. A high jumper might want to ramp up the forces by using a high fall and focusing on the height of the jump. They are high jumpers after all so at some level focusing on height makes sense. But elite high jumpers see contact times under 180ms in their jump. Prescribing such training, with more than double the ground contact time, isn’t going to be training the same stretch shortening cycle they need for their event. Similarly, if we are doing a reactive strength index test and do not instruct athletes appropriately, we won’t actually be measuring reactive strength. On the other hand, in sports that utilize more of the long stretch shortening cycle might find they need different instructions to achieve their goals.
In all cases, coaches need to be aware of the power of a few words. And feedback is critical as well. Coaches need to keep their eyes open to see if the exercises they select are being executed in a manner that will reach the intended training goals. And, as Young notes, external feedback is also helpful. Showing athletes their contact time, jump height, or RSI after each attempt can help optimize the elements you are looking for.
