Maximising vertical jump training with accentuated eccentric loading

Finding ways to improve vertical jump (VJ) performance is a popular talking point among coaches and athletes. This ultimately comes down to the correlation between variants of a VJ and athletic performance during competition, namely, sprint and change of direction tasks ^[1,2].

Traditional strength training, weightlifting, plyometrics and ballistic training are effective methods of improving the VJ ^[3,4,5]. However, there comes a time in an athlete’s career when a coach needs to introduce new and varied approaches to drive continual neuromuscular adaptations and long term progression of athletic performance.

Accentuated eccentric loading (AEL) fulfils this objective, especially when applied to a countermovement jump (CMJ). Succinctly, an athlete holds an additional mass during the countermovement that they subsequently release before executing the propulsive action ^[6,7].

Coaches and athletes use this training method, but there is still a need for recommendations around training prescription and how AEL can be implemented into practice ^[6,8,9]. The following sections summarise best practice guidelines from my experience working with amateur to elite soccer players from U14s through adults.

Please note that the data in this article was collected from these players in practice and a pilot study only. None of the data is published yet.

AEL takes the countermovement up a notch

We know from both research and experience that athletes jump higher when they perform a countermovement prior to their propulsive action ^[10,11]. Asmussen and Sorensen ^[12] originally introduced this concept by investigating a horizontal pulling exercise in 1971, naming it the “wind up” movement, and found that it facilitated a greater level of force at the start of propulsion.

Mechanically, it represents the amount of energy in the system at the bottom of the countermovement ^[13]. The greater this value, the more energy our athletes have – that is, more capacity to do work – to take forward into the propulsive action. If an athlete holds additional mass during the countermovement phase of a CMJ, they must apply an even greater force to the ground to decelerate the downward movement. Given that they enter the propulsive action without the additional mass, but having applied a higher level of force, they should be able to accelerate their centre of mass more effectively to jump higher.

In theory, the mechanisms underpinning a CMJ with AEL should be similar to those during an unloaded CMJ, but greater in magnitude ^[14].

Key coaching points for accentuated eccentric loading

To ensure that the concepts behind accentuated eccentric loading transfer into practice, coaches should adhere to the guidelines.

Familiarisation: Sitting vs. folding

This distinction is based on terms we’re borrowing from Hailu Theodros in a Pacey Performance Podcast. Speaking about change of direction and deceleration drills (see clip below), Theodros refers to a knee dominant squat pattern as “sitting,” as opposed to a hip dominant hinge pattern that he calls “folding.” The former is his criterion of superior performance.

These terms resonate better with athletes than “squat” and “hinge,” and coaches should consider that saliency.

To achieve the desired movement coordination and quality, a coach must familiarise and instruct their athletes appropriately. I have witnessed athletes master a CMJ with AEL from the get-go. But more often than not, they require a number of sessions and trials to truly grasp it.

From an understanding of joint and muscle work during exercise, a coach can make more informed decisions when prescribing an exercise.

Hip, knee and ankle joint contributions during an unloaded CMJ are ~32%, 42% and 26%, respectively ^[15]. This is in agreement with other studies that have noted the vastii muscle groups make significant contributions to centre of mass acceleration during a CMJ ^[16]. It would make sense for a similar pattern to be observed during CMJs with AEL, given that the only difference lies simply in the additional mass during the countermovement. This is supported in musculoskeletal simulations of AEL during a CMJ ^[17], although experimental evidence is needed to draw a firm conclusion.

Our unpublished data suggests that a “folding” pattern is detrimental. In fact, one of the key differences between a good jumper and a poor jumper in the context of AEL is the ability to remain active through the knee extensor muscles. That is, they adopt a “sitting” pattern. If an athlete folds at the hips, they lose vital input from the knee joint that serves to enhance work during the propulsive action.

Let’s not forget an athlete’s level of strength. I would be lying if I told you that it doesn’t make a difference. Our stronger athletes master these techniques sooner and respond more favourably from an acute and chronic standpoint. However, that’s not to say that “weaker” athletes cannot or do not do it. There is just a higher emphasis on familiarisation and coaching. I’ve also worked with numerous individuals who arrive with a wealth of plyometric and ballistic training experience, but very limited exposure to strength training. In their cases, it may be viable and sensible to add AEL to their CMJ.

Below is a process that coaches can adopt to introduce CMJs with AEL to an athlete. These are briefly introduced here but will be discussed in more depth later.

Mastering the release

Without a doubt, the most important yet overlooked quality of a well executed CMJ with AEL is releasing the additional mass at the correct time.

We almost always use dumbbells, as they are easy for our athletes to grab and get started. However, alternative equipment such as resistance bands, kettlebells, a trap bar, and a barbell with weight releasers are all useful options.

An athlete needs to release the dumbbells or whatever other implement as close to – if not precisely at – the bottom of their countermovement. If they release too soon, the likelihood of a beneficial stimulus diminishes rapidly. If they release too late, the propulsion phase will be compromised. Either way, they fall short of the maximum possible benefit, and their output will be an uncoordinated jump pattern: what our athletes call the “ugly ones.”

The crux is that release point is notoriously difficult to quantify. Ideally, you have a 3D motion capture system or high speed cameras and a force plate. These would need to be time synchronised and sampling at the same rate to prevent errors stemming from mismatched data.

If you don’t have access to this kind of equipment, you can use a linear positional transducer (LPT) to obtain dip or negative displacement. Of course, this process won’t be as accurate. However, data can be collected simultaneously from an LPT and high speed video to gain an idea of where our athletes are releasing the dumbbells relative to their peak negative displacement, that is, their lowest position.

If you are lucky enough to have some or all of this equipment, you will know that it’s particularly limited in practice. Coaches have a limited amount of time working with their athletes and are expected to deliver, so I have generally relied on a smartphone camera or real time observation.

I record on my Samsung A53 5G in full HD at 30 frames per second. Luckily, blurriness isn’t an issue as long as a little bit of time is spent on selecting the optimal recording mode and camera positioning. CMJs are not actually that fast compared to other sporting actions that are characterised by rapidly moving limbs, such as sprinting. If you’re the type of coach who likes to spend your evenings processing data, then you can also upload your video footage into free software such as Kinovea and then carry out further analyses.

Coaches can record in the sagittal plane and slow down the footage to ensure that the athletes are releasing the dumbbells at the correct time while executing a “sitting” pattern. With experience and a good coaching eye, the difference between a good jump and a poor jump is clear, even without video review or analysis (Video 3). 

The following data set (Table 2) is an example of integrating smartphone camera footage and an LPT. These were recorded across three sessions, separated by seven days.

The most important takeaways here include:

1. Over the course of the nine trials, the athlete releases the dumbbells closer to their lowest position.
2. Releasing closer to the lowest position results in an improvement in jump height, as we can see in trials 7-9.
3. Releasing after the lowest position has the most detrimental effect on jump height.

To ensure that athletes release at the correct time, regardless of the equipment used or the jump that we are adding AEL to, appropriate instruction is vital.

Instinctively, most coaches want to cue their athletes to release the additional mass at their lowest position. However, this relies on our athletes having a good understanding of what or where their lowest position is. Therefore, coaches should simply tweak this to “release the dumbbells (or whatever additional mass) immediately before commencing upward movement.”

Unless the coach ensures that their athletes release at the correct point in the movement, the likelihood of seeing benefit from this training method is minimal. Now, let’s not get carried away. I acknowledge that there is much more to a CMJ than height. But until someone researches the specific strategy athletes employ during a CMJ with AEL, we are none the wiser.

Maintain depth while lowering greater load

Limited investigations have explored CMJs with AEL, and of those that have, the findings are mixed. Some studies have found the addition of AEL to be beneficial ^[18,19,20], while others advise against it based upon the disruption to movement coordination ^[6].

During an unloaded CMJ, an athlete’s lowest position is typically quite consistent. Add the AEL stimulus and this can change quite dramatically. For the most part, the addition of dumbbells during the countermovement results in a shallower displacement. When we consider the fact that a larger countermovement generally increases jump height ^[21,22], this is a problem that coaches need to address.

If an athlete’s lowest position during an unloaded CMJ is -0.35m and they jump 0.45m and we ask them to perform the same jump but with a shallower countermovement, they probably won’t jump as high. This is no different to what we see when we first add AEL to a CMJ (Table 3).

In Table 3, we can see how this plays out over the course of a seven week training intervention. For reference, this athlete’s “normal” CMJ lowest position and height range from -0.34 to -0.37m and 0.43 to 0.45m, respectively. The intervention simply consisted of adding two sets of four repetitions of a CMJ with AEL (using dumbbells) to their normal strength and plyometric training programme. This was progressed after each testing occasion to three sets of four and, finally, four sets of three (we’ll get into selecting an appropriate dumbbell mass later).

Despite only considering one athlete, the changes are clear. The athlete’s lowest position increased at each testing occasion and so did jump height. Changes in an athlete’s lowest position is supported in research following 10 weeks of light  and heavy load ballistic training ^[23], but this needs to be investigated following a jump based AEL intervention.

Coaching cues for optimal movement quality

An athlete is normally cued to perform the CMJ “as fast and as high as possible with your preferred depth” ^[24,25,26]. My experience tells me that if the same is applied to a CMJ with AEL, most athletes won’t respond favourably.

As we have already covered, one of the main issues when we add this stimulus is that an athlete will shorten their countermovement. If we cue them to lower to their preferred position, it likely will be significantly shallower than their normal strategy or the one that we call “optimal.”

The focus on executing the countermovement “as fast as possible” also seems to cause some problems. Long term, we want our athletes to perform the countermovement quickly with the additional mass. But if a coach introduces this movement to their athlete(s) for the first time, a focus on “fast” movement speeds results in a disjointed and uncoordinated jump pattern.

For this reason, “perform the countermovement at your maximum comfortable velocity and release the additional mass immediately before commencing the upward movement to jump as high and as fast as possible” seems to work best.

Jumping “as high as possible” is important, but “performing the countermovement at a preferred velocity” is the key.

In as few as three practice trials, an athlete will start to understand and gain control of their “comfortable” countermovement velocity. If they move too fast, they incidentally end up performing a shallow countermovement and releasing the dumbbells too soon. My current theory on this is that the dumbbells alone feel uncomfortable at first, so if we couple this with encouraging “fast” movement speeds, an athlete will naturally avoid a deeper countermovement. On the other hand, if an athlete performs the countermovement slowly, they actually release the dumbbells too late and go through a much larger range of motion.

Once an athlete begins to master the movement, coaches can shift to a simpler cue each time a CMJ with AEL is added in practice. For example, we use “unload fast, brake hard, release and jump high” to remind our athletes of the key components that they need to get right. If the intended application is an alternative variation of a VJ, then we can use the cues in Table 4. These are based on our observations and experience in practice. However, coaches can manipulate them as they see fit and in line with research ^[27,28].

Coaches also need to emphasise the importance of attaining a similar low position between an unloaded CMJ and a CMJ with AEL.

Selecting the loading, rep and set scheme for accentuated eccentric loading

Effective training requires the selection of a suitable mass. The most researched loads are 10-30% of body mass for CMJs with AEL ^[18,19], while others have experimented with fixed dumbbell masses of 15kg ^[6].

I have tried everything from 10%-50% of an athlete’s body mass, mostly with dumbbells. Anywhere between 20-30% of body mass facilitates the greatest improvement in jump height and least disturbance to movement strategy, i.e., the athlete adopts a sitting pattern and releases the dumbbells at their lowest position, similar to their unloaded CMJ.

If the dumbbell mass is below 20% of body mass, the stimulus isn’t sufficient to evoke a performance improvement and the athlete’s strategy will back this up, likely because the additional mass is too light. Anything above 30% of body mass and an athlete will generally do one of two things: 1) a shallow countermovement, as a lower position is uncomfortable and requires more effort to undertake; or, 2) they fold at the hips and perform a hip hinge pattern.

Coaches also need to consider their athletes’ level of strength when implementing a CMJ with AEL. Figure 3 displays a comparison between two athletes. Athlete 1 responded best at 20-25% of body mass, whereas Athlete 2 jumped higher at 30-35%.

These differences stem from the fact that Athlete 2 is relatively stronger than Athlete 1 (1.7x BM vs 1.1x BM, respectively) and was also able to jump higher during an unloaded CMJ.

Another point for coaches to consider is that at higher percentages of body mass, Athlete 1 experienced a sudden increase in movement time prior to take-off. Given the simultaneous drop in jump height, this athlete likely was unable to continue their preferred jump strategy, highlighting that the carry over to physical performance tasks may be restricted.

If a coach is working with a small number of athletes, incorporating CMJs with AEL is straightforward. On the other hand, working with a large number of athletes can be problematic.

For example, I recently worked with a U18s soccer team, and 12 out of 16 players were 70-80kg. A coach in this situation looking to implement CMJs with AEL at 20% of body mass confronts the fact that all 12 athletes will need a pair of 7.5kg dumbbells. Logistically, this is a nightmare.

To overcome this, we routinely group athletes according to their body mass and use cluster sets ^[29]. This enables a coach to have 3-4 athletes performing a CMJ with AEL at the same time: one athlete jumps and rests 15-20 seconds, which is sufficient time to allow the other three athletes in the group to perform their jumps.

An example of how we integrate this into our annual soccer programme is in Table 5, with example sessions in Tables 6 and 7.

The rationale is that an athlete will develop their ability to exert force during the braking phase first, before moving into a focus on enhancing rate of force developing. Both characteristics are key determinants of not only CMJ performance ^[30], but also other physical performance tasks such as change of direction speed ^[31]. This brings the implementation of AEL with CMJ in line with how coaches incorporate plyometric training.

Alternatively, a coach could pair athletes (again, according to their body mass) and have them perform a rebound CMJ with AEL (Video 4). These simply add 2-3 unloaded rebound jumps to a CMJ with AEL. Depending on the intended outcome, these can be performed with minimal ground contact time or with the aim of attaining maximum jump height (similar to a drop and depth jump, respectively). The advantage of this exercise is that an athlete can grab a pair of dumbbells, perform the movement, and another athlete can be waiting to pick up the dumbbells and go.

A final application of jump based AEL we regularly call upon in training is post-activation performance enhancement (PAPE) ^[32]. In keeping with matching the biomechanical demands of the conditioning exercise and intended application ^[33], Table 8 provides examples of how an AEL stimulus can be added to a CMJ and then paired with a physical performance task. The specific volume, intensity and recovery periods you program will depend upon factors like your athletes’ training experience, competitive level, strength and phase of training. Therefore, we recommend a period of experimenting before adopting any one of these methods.