Plyometrics in Tennis: Science, Research & Application
I’ve been asked countless times - from tennis coaches, to players - and even parents - 'how can I get more leg drive on my forehand?' 'Or more jump from the legs on my serve?' 'Or more explosiveness when moving laterally?' There’s no simple answer. It truly depends on a number of factors, including your strength levels, coordination, training age, biological age, training history, genetics and more. But if I absolutely had to boil my answer down to one form of training, I’d have to look towards plyometrics.
There are many terms to describe plyometrics including plyometric training - ‘shock training’ (originally what the Soviets called it) and ballistic training are 2 that some coaches use. I like to simply refer to them as ‘plyos’. Whatever you call it, the basic premise is to increase various performance factors (like power output, elasticity, tissue tolerance and more). You’ve probably heard or seen this type of training in action or have done different forms of it yourself. But what is it exactly? Why do coaches prescribe it? What are the benefits? And how can tennis players use it effectively to improve movement or hit bigger shots?
This article will define plyometric training and the basic science behind it. Many believe that plyos are only implemented during jump training for lower-body explosiveness but that's not exactly true. Upper-body plyos can also augment power in the upper extremities. However, in terms of the research and application that'll be presented in this post, the focus is on lower-body plyometrics.
The Physical Demands of Tennis - a Brief Review
Before we continue, a quick reminder, tennis is physically demanding. It’s an intermittent sport characterized by short high-intensity bursts of effort followed by short recovery times (Kovacs 2007). The majority of movements occur within 3m; these movements are explosive and powerful (Reid 2007) - you can’t play at a high level in today’s game without these two qualities. Furthermore, within one single point, players change direction multiple times and thus require the ability to accelerate, decelerate and reaccelerate quickly, while optimizing time. Coaches have been using plyometrics for years to enhance these qualities in players.
What is Plyometric Training?
Plyometric training is rooted in European - or more specifically - Soviet, sport science research and application. Plyos are frequently incorporated into athlete’s training programs because of their proposed ability to increase explosive actions. Plyometric exercises involve a rapid stretch - eccentric contraction (ECC) - of a muscle-tendon complex followed by an explosive shortening - concentric contraction (CON) - of a muscle-tendon complex. This is termed the stretch shortening cycle (SSC) - stretch being the ECC phase and shortening being the CON phase. While not plyometric, an example of the SSC is a simple countermovement jump - like this:
Please note, this article was written in 2018 - I have since gained a greater understanding of ploys and will soon be publishing an updated article on the topic. That said, this post is a good starting point for many who are new to plyometric training - along with the proposed mechanisms.
During the lowering phase (ECC), a stretch of the muscle-tendon complex occurs during the jump. This is followed by a rapid CON contraction - the acceleration/take off phase of the jump. SSC actions are similar to movements encountered in sport (Markovic 2007), another factor that has contributed to their widespread use and popularity. It’s proposed that SSC efficiency is enhanced after plyometric training because of an increase in neural drive, rate of neural activation and intermuscular coordination.
There are countless examples of plyometric exercises. Some of the most common ones include multiple jumps, bounds, hops and depth jumps. Although commonly used by coaches to increase performance, everyday activities like walking and running also involve the utilization of the SSC - but again, they are NOT all plyometric.
How Exactly Does the SSC Work? Mechanisms
The SSC is based on a number of factors. The basic mechanism being the storage and reutilization of elastic energy. You absorb energy during the ECC pre-stretch and follow that with the release of energy through the shortening CON contraction. It’s important to note that (almost) all movements have an eccentric, isometric and concentric component to them but when we refer to the SSC - in the case of plyo training - we’re talking about using potential energy to propel our bodies (or body segments) with power (the intent of our actions will dictate how much energy we store + utilize).
Neural Potentiation
Because the movements occur at a higher speed, there is a high demand for high threshold motor unit (MU) recruitment. Remember, these are the MUs that are associated with type 2 muscle fibres, the ones that generate more force, at faster rates and are associated with powerful, explosive movements. And they are highly targeted through plyo work - unlike long-distance running, which will primarily target type 1, slow-twitch muscle fibres.
Muscle Spindles
Think of a knee jerk action. When you stretch the muscle tendon complex to a near damage point, muscle spindles - which are classified as sensory receptors - in the muscle belly detect this length change. One role of muscle spindles is what’s called the stretch-reflex - in which a signal is sent to the spinal cord when a change in length and/or velocity is detected. This stimulates and opposing concentric contraction of the agonist muscles. This knee-jerk action-reaction occurs during plyometric activities.
Stretch Shortening Cycle (SSC) Classification - Slow vs Fast
Many sport scientists have distinguished plyometric activity through 2 SSC classifications - the slow (or long) SSC component and the fast (short) SSC component. Knowing the distinction between the 2 is critical to effectively implement plyometric training into a tennis player’s program.
Plyometrics and the Slow SSC
Slow SSC activities are characterized by longer contraction times (>250 msecs) and therefore a longer ECC (or lowering) phase. This means that slow ECC actions have greater angular displacements at the hip, knee and ankle and because of these attributes, can develop greater force. Think about a vertical jump, if you wanted to jump as high as possible, you wouldn’t do it with a quick ECC action (if you did, you’d jump quickly but wouldn’t reach your max jump height). You’d bend your knees more and have a longer lowering phase. At the same time, if you take too much time going down (or even stop at the bottom of the movement), you’d lose the SSC’s elastic energy and again, wouldn’t jump your highest. On top of that, multiple consecutive jumps allow for greater storage + release of energy, thereby augmenting the potential to produce power (i.e. jump higher, further, get off the ground faster and so on).
The SSC is of high importance during the leg drive and push-off phases of big forehands.
The Role of the Slow SSC in Tennis
In tennis, the slow SSC component does play a vital role in certain situations. Serving and hitting forehands are prime examples. For instance, when serving, you don’t want the loading phase of the serve to be too quick or too long, you’ll lose power output in the latter and won’t optimize it in the former. It’s this ability, however, to load the legs optimally, storing potential energy, that allows a tennis serve to be the biggest weapon in a player’s game. That potential energy then gets transferred from the legs and hips, through the torso, and into the arm action of the serve. This is referred to as the kinetic chain - and it sets the stage for efficient, powerful tennis strokes. Just look at the two videos below. What's important here is the time component - both movements require the development of more force so a slower ECC phase is necessary.
Similarly, certain instances of the forehand utilize the slow component of the SSC...like the attacking forehand (image of Halep above). When attacking, a tennis player wants to put some punch behind their shot, as to put his/her opponent on defence - or to hit a winner. It’s important to have some speed on the ball but the only way to do that is to load the legs appropriately.
Many coaches believe players need to use an extreme knee bend on serves and forehands to generate enough power. This is not true. From a mechanical perspective, potential energy will leak if too much knee bend is present.
On the other end of the spectrum, not enough knee bend will also result in sub-optimal power output. There is a balance, and in fact, each player is different. Coaches should be wary in group settings as to not ask each player to have identical, perfect knee bend, when loading the lower-body.
Plyometrics and the Fast SSC
Then there’s the fast SSC component. Fast SCC activities are characterized by shorter contraction times (<250 msecs) which is reflected by short ground contact times (GCT). Short ground contact times are more common during sporting movements, including many actions involved in tennis. In contrast to the slow SSC component, a fast SSC has smaller angular displacements of the hips, knees and ankles. This makes sense as these activities are quicker in nature so athletes don’t have as much time to load up before executing a movement (think about a basketball player fighting for a rebound or the split step in tennis - for optimal results, both need to be executed quickly). Less force is developed with the fast SSC (and therefore lower jump heights, for instance) but there’s a greater rate of force developed - i.e. how quickly you can develop force - which is crucial for the majority of tennis movements.
The Role of the Fast SSC in Tennis
I’d argue that more movements in tennis require the fast SSC - players don’t need to develop max force but they do need to develop enough force to perform a certain movement - so there’s still a minimum amount of force required - and that force must be developed in the shortest possible time frame. If a player has the capacity to do this, you'll see very fast, explosive movements to the ball, razor sharp changes of direction and more. RFD is also important in various groundstroke situations - when the oncoming ball has a lot of speed and a player must prepare quickly and develop enough force to send the ball back with some heat. And remember reactive strength? This quality is necessary for EVERY split-step in tennis. Check out the videos below - both movements require reactivity. In the depth jump, it's to get on the 2nd box as fast as possible while a reactive split-step initiates a more explosive lateral movement.
The Research on Plyometrics
Plyos and Tennis
So what does the research say about plyos in tennis? Interestingly enough, when 12 highly ranked ITF (International Tennis Federation) tennis players (ages 13-16) went through a battery of tests, sprint & vertical power abilities revealed a significant positive relationship with their ITF ranking position (Filipcic 2010). The authors suggest that faster players who can also jump higher, end up having higher rankings. This implies that by possessing these qualities you’ll get to the ball faster, set-up better and recover for the next shot more efficiently. If you can do that more often during a match, chances are you'll do well.
Another study found that nine weeks of either plyometrics or a combined plyo and tennis training program, in novice tennis players, improved various measures of strength and power (Salonikidis 2008). While young competitive tennis players improved COD ability following 6 weeks of plyometric training. So both beginners and more experienced players can benefit from jump training. Anecdotally, coaches have been using plyo training to improve player performance for years but it’s unfortunate that when it comes to research, tennis and plyometrics have been historically understudied.
Plyometrics and Other Sports
Because so little research exists on plyometrics and tennis, we'll draw examples from other sports. In adolescent high school basketball players, vertical jump ability improved significantly after only 6 weeks of frontal plane plyo training while no improvement occurred during sagittal plane plyos (King 2010). Although there’s a heck of a lot more jumping involved in basketball when compared to tennis, both sports have similar requirements in terms of COD, acceleration/deceleration and explosiveness. Even a low-intensity plyometrics program performed once a week improved vertical jump; as seen in 13 year old female soccer players (Rubley 2011). However, lower intensity programs will likely only work if 2 conditions are met - a) the players are beginners and b) the program has a long enough duration (in this study, they trained for 12 weeks).
In other athletic populations, elite handball players improved vertical jump height after 12 weeks of combined plyo and speed training compared to a control group (Cherif 2012). Thomas et al (2009) compared 2 different plyo programs - drop jumps (DJ) versus CMJ (countermovement jump) training - in elite soccer players and found that vertical jump ability and agility significantly improved in both groups after a short 6 weeks plyo training program. No improvement occurred in sprint performance following the preceding plyo programs but it may be necessary to perform plyometric exercises in both horizontal and vertical directions for speed improvements to occur as this would follow the specificity principle,
In experienced male soccer players, speed and power improved after 8 weeks of DJ and hurdle jumping; both forms of exercises include plyometric actions in horizontal and vertical directions, with small ground contact times (super important for the development of reactive abilities in tennis), and likely provide a better transfer to both running and jumping (Chelly 2010). Are you noticing a pattern here? Including a variety of plyometric drills, in a variety of directions and planes of motion, can improve jumping ability, COD ability and sprint speed. Even short term programs, 6-12 weeks, along with frequent exposures - 2-3 days/week - can see big gains in performance. Where do I sign up?
Plyometric Training Implications for Tennis
Now that we know the research on PT, along with the differences between the fast and slow SSC components, questions begin to arise. How do we use PT effectively? What does the training look like? Where do we begin? How do they integrate into a long-term program? And so on.
Early Phases of Training and Young Athletes
Although the fast SSC component is more relevant in most athletic movements where producing force quickly is of greater concern (Flanagan 2008), programs should first focus on exercises that target the slow component before moving on to fast component exercises. This elicits a better transfer from the former to the latter - i.e. slow SCC activities develop more max force while fast SCC develop RFD (and RFD is maximized when an athlete can produce high levels of force & power).
When beginning a program, especially if you or your athlete have little experience with off-court training, I can’t stress enough how critical it is to begin with slow SSC activities, at lower intensities and appropriate progressions. The tendency is that most coaches want results RIGHT AWAY and jump into plyometric activities that are way too advanced. I’ve trained pro players (ATP + WTA), along with highly ranked ITF juniors (U18) and most weren’t ready for fast, explosive plyometric work. Look how simple plyos can be even at the elite level:
So in the beginning, coaches must focus on jumping and landing techniques, similar to the video above, controlling the landing. This is done in a single leg manner but can also be done in a double leg variation. Once this ECC landing is executed to an acceptable level, then we can move on to more complex drills (video below). If landing poses a problem for an athlete, they won't have the prerequisite ECC strength to store energy and then release that energy into an explosive action. Landing can also be done from a standing position or off of a box - both are important in the early part of a program.
Once some general jumping and landing mechanics have been established, players can begin to progress their plyometric training. This usually includes a variety of fast component drills. At this time it’s still important to maintain the slow SSC activities in the program as to not lose that quality. Examples of fast ECC exercises include hurdles, depth jumps, reactive hops etc. and can be done moving horizontally, vertically, laterally or in a multi-directional fashion.
Principles of Training...Respect Them
I've spoke many time about specificity, progressive overload, variation and individuality - refer to those articles for detailed descriptions. Here's a brief outline of each principle as it relates to plyometrics.
Specificity
You may still be wondering how plyos transfer to the tennis court? Let’s take serving as an example. How does plyometric work transfer to the serve? Let’s say you serve 100 balls. That’s also 100 jumps. That in itself is a form of plyometric work. However, if a player cannot get enough power on the serve, he/she must first train basic jumping and landing movements. You don’t have to mimic the exact movements that are involved in serving within the off-court training session, you’ll get that specificity through serving. Make sure the physiological and mechanical qualities you’re looking to improve, like RFD, reactive strength, power, are targeted during the training session, and continue sport practice. Transfer will come.
Whether it’s a serving drill, footwork drills or whatever else, too often coaches try to simulate movements in training that are similar to actual tennis movements. This is redundant. I have coached in academy settings where kids were playing between 2-5 hours of tennis a day. There’s enough footwork drills in their actual play to improve that quality. Look at the demands of the sport and train the physiological, mechanical and metabolic characteristics of the sport.
Ok there are times when simulation is good. These exercises are called special strength exercises. But there is still an external resistance added to these movements to act as an overload. This is the best quote I’ve seen on the topic, from Elite Track:
“Just because an exercise looks like the event doesn’t make it effective. Likewise, just because an exercise doesn’t look like the event, doesn’t make it ineffective. Using different exercises while maintaining specificity can also aid in reducing overuse injuries and maintaining freshness in training". Full article at Elite Track.
Progressive Overload
This is an important principle and should not be taken lightly as there is a high neural demand during plyometric training. Progress the athlete cautiously. In the case of plyos, progressive overload is not generally done through added weight. In contrast to weight training where that is in fact the case, plyo training can be increased with volume (more jumps per session, per week or per training cycle) or intensity (hurdle/box heights, exercise complexities, single vs double leg variations and so on). This is where the concept of ground contact times comes into play. You are literally counting the number of jumps the athlete does in a particular session, week and competitive cycle.
Furthermore, a concurrent strength & plyo training program may help attenuate injury while acting as an additive effect to power production. Some researchers argue that possessing a high level of strength should precede a plyometric training program but I tend to disagree. Yes general strength exercises are important when first starting an off-court program, we perform plyos regularly since the day we first start walking. Running is plyometric. Jumping around on the playground is plyometric. Swinging your arms from a tree branch is plyometric. Young kids perform these movements from an early age (or at least they used to). As long as proper progressions, intensities are used, there should not be any adverse effects from plyometrics in younger populations.
Individuality & Variety
Each athlete is different and will have different needs. Some may jump high while others may jump quickly. Know the difference. This will help individualize the program based on the needs of the athlete, not only the sport. Figure out if they can jump off 1 leg or 2. Can they jump backwards? Tennis play is multidirectional - players move forward, laterally and backwards - plyos can target the physiology of all these movements. How old are they? What’s their training age? Have they done plyos in the past? What’s their competition schedule? All of these factors need to be taken into consideration.
When it comes to the principle of variety, caution must be taken. Variety does NOT mean changing the exercises every day, week or cycle. If the athlete has improved because of a plyometric program, then it may be time to add new exercises or loading schemes, not before and certainly not when you feel like it.
Training With Intent
One point we must consider when it comes to training, whether it’s on the tennis court or weight room, is the intent of the athlete. Yes, running is a plyometric activity, but running at a slow speed won’t have the same effect as running maximally. Similarly, if you’re performing jump training, the intent must be high for the greatest gains in performance.
Research suggests (Cormie et al 2011) that the intent to move explosively can in many cases be just as important as actually moving explosively. That’s why strength training works so well. It won’t make you slow, if you a) combine it with other forms of training, like plyos and b) have a super high intent to move the load as fast as possible (whether you actually move it quick doesn’t matter) - as it will nonetheless improve explosive qualities.**
**also why weightlifting is so effective - it’s highly explosive, utilizes the SSC, and the ECC landing component is loaded - this helps players gain more capacity to handle high loads…and the amount of force an athlete must absorb when decelerating can be several times higher than their bodyweight...another reason lifting works!
There’s a lot of info here so reach out if you have questions or leave a comment at the bottom of this page. If you're going to implement plyometrics with tennis players, probably the most important thing to consider early on is jumping and landing mechanics along with ground contact times. Too much plyo work, performed incorrectly, can harm players, both at a tissue level and a burnout level (plyos exhaust the CNS). Too little stimulus and you won’t see a training effect. And remember, intent has to be high with all activities - both on-court and in the gym - to realize the positive adaptations from explosive training.
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