Properly Programming PLYOS: Far More Than Just Jumping

As popularized by the athletic community, lower body plyometrics are speed and power-based exercises in which the muscles exert maximal force in minimal time by stretching and contracting repeatedly. Although there’s some debate as to what constitutes a “true” plyometric exercise, their value for all things related to athletic performance – like sprinting fast, jumping high, throwing down huge dunks, and hitting moon shot home runs – is one of the most widely accepted truths in all of strength and conditioning.

That being said, plyometric training isn’t just for athletes. In fact, it might be even more important for everyone else. Since lower body plyometrics build power – which is correlated with things such as strength, body composition, and longevity, among others – everyone from washed-up meatheads to grandparents should be performing them in some way, shape, or form. Here’s why:

Athletic performance. As mentioned, lower body plyometrics are a must for athletes to bridge the gap between strength in the weight room and athletic performance on the field or court. Ultimately, they pave the way toward faster sprints, higher jumps, enhanced reactive/elastic strength, and more raw power as a whole.

Strength. Many lifters and gym-goers are quick to dismiss the speed qualities at the far end of the force-velocity curve, despite the fact that the ability to exert force quickly (AKA, power) may make the difference between hitting a PR and getting buckled underneath the bar. While dynamic effort lifting is one way to target speed-strength, lower body plyometrics are in a category of their own for improving pure speed and rate of force development due to their unparalleled movement velocities.

Body composition. Fast concentric actions target the type II “fast-twitch” muscle fibers that have the most potential for muscle growth, which means that plyometrics performed prior to training can increase muscle recruitment while training, and thus facilitate more muscle growth over time. Power-based movements have also been shown to elevate basal metabolic rate post-workout, which can aid fat loss efforts.

Central nervous system activation. Performed in the last phase of the 6-phase dynamic warm-up, lower body plyometrics are perfect for firing up the central nervous system and locking in solid movement mechanics prior to smashing big weights on leg day.

Joint and connective tissue health. When performed and progressed appropriately, lower body plyometrics are phenomenal for strengthening the joints and connective tissue, improving tendon health, teaching proper force absorption, and building resilience.

Aging and longevity. Studies show that humans lose power almost twice as fast as strength as they age – 1.7x, to be exact – which makes developing lower body power essential considering its correlation with just about every longevity-related metric in the book such as quality of life, fall risk, injury prevention/reduction, hormonal health, all-cause mortality, etc.

However, not all plyometrics are created equal, nor should everyone follow the same plyometric prescription. Thus, the key to maximizing the safety and effectiveness of plyometric training for yourself or your clients/athletes lies in understanding the “what,” “why,” and “how” behind the best practices for assessing, applying, and performing lower body plyometrics.

General Guidelines For Plyometric Training

Although there are plenty of factors to consider when prescribing and performing lower body plyometrics, the following three guidelines are the foundational tenets of safe and effective plyometric training.

  1. Earn the right to jump by learning how to land

Just as you wouldn’t get into an airplane with a pilot who doesn’t have their landing license, nor should you dive headfirst into plyometrics without first learning how to land well. After all, the large majority of plyometric-related injuries have been shown to stem from poor landing abilities and lackluster eccentric strength, which makes developing a solid foundation prior to plyometric training a must.

Above all else, it’s pivotal to 1) build adequate eccentric strength, 2) learn how to absorb force properly, and 3) employ good landing mechanics, which means jumping and landing from the same position, avoiding hip and knee flexion angles beyond 90 degrees, landing smoothly, and “putting on the brakes” upon impact.

  1. Quality over quantity

Like anything else, prioritizing quality over quantity is paramount for maximizing the safety and efficacy of plyometrics. That means jumping with maximal intent, resting as needed between sets and reps, maintaining proper jumping/landing mechanics, and keeping the volume low and intensity high.

  1. Remember that the goal is to train

Lower body plyometrics aren’t about getting “dope” footage for IG or attempting to hit box jump PRs while risking death in the process, but rather about developing lower body power while getting the body prepared to throw around some iron. While some athletes with certain needs and goals may need more specific prescriptions than others, the truth is that, for the vast majority of individuals, lower body plyometrics are just one piece of the puzzle within a synergistic, multi-faceted training system. Beyond power development, their purpose within the 6-phase dynamic warm-up is to prepare for and enhance the training session that follows, which means that they should be treated (and programmed) as such.

The Primary Variables of Progression: Eccentric Stress and Complexity

Regardless of where a movement falls on the basic-to-advanced continuum, there are two overarching variables that can be manipulated to progress (or regress) the intensity and difficulty of plyometrics. The first variable is eccentric stress – or the extent to which gravity enters the picture – which varies based on the amount of force that’s imposed upon the body at ground contact. The second variable is complexity, which – as its name suggests – refers to the mixing and matching of certain elements to increase or decrease a movement’s complexity.

Taking both variables into account, the following guidelines can be used to progress or regress any given lower body plyometric regardless of its initial position on the basic-to-advanced continuum.

Bilateral before unilateral. Bilateral plyometrics are simpler, easier to perform well, and less eccentrically demanding than their unilateral counterparts due to the dissipation of force between both limbs as opposed to a single limb.

Vertical before horizontal. Whereas jumps performed vertically only require force absorption and deceleration in a single plane, broad jump variations require the body to absorb force both vertically and horizontally, which ups the eccentric demands and increases their complexity.

Linear before lateral (most of the time). Like horizontal jumps, lateral jumps require the body to absorb force in two planes – and thus require more eccentric strength – while throwing in added elements of multi-planar coordination. Excluding athletes who have to jump, land, and decelerate across multiple planes regardless of their training experience, most individuals are better off mastering linear jumping and landing before moving onto lateral alternatives.

Unloaded before loaded. It goes without saying that loaded plyometrics impose more eccentric stress than their unloaded counterparts, which makes load an obvious form of progression. That’s not to say that loaded plyometrics don’t have their place, but rather that their increased eccentric demands should be taken into account when progressing or regressing certain movements.

Single-response before multiple-response. Single-response movements that involve a full reset between reps are generally easier to control and more effective for establishing good mechanics than multiple-response movements, which involve continuous movement and minimal ground contact times (e.g., triple broad jumps).

Static before dynamic. In general, starting with static (paused) jump variations before moving onto dynamic movements ensures the “owning” of certain positions and encourages better jumping and landing mechanics.

Plyometrics Overview: Phases 1-4

Although there’s no set-in-stone method for categorizing lower body plyometrics, there are four general phases, so to speak, that most plyometrics can fall into. The first two, which comprise of eccentric- and concentric-focused movements, are often referred to as basic jump training. The third and fourth phases are more in line with “true” plyometric training – as defined by an amortization phase of 0.2 seconds or less – since they involve minimal ground contact time and greater intensity and/or complexity.

As mentioned previously, the factors that influence eccentric stress and complexity create some gray area within each phase, which means that both variables should be considered when progressing or regressing movements. From an eccentric stress standpoint, it’s crucial to progressively increase the type and amount applied not only to reduce injury risk, but also to help connective tissue develop more spring-like qualities – which makes it more pliable and elastic – and thus increase its ability to withstand greater eccentric demands. From a complexity standpoint, individuals who are new to plyometric training are generally better off starting with simple movements that have a lower learning curve, whereas those who are experienced with plyometrics are typically able to handle complexity more effectively.

Ultimately, accounting for both variables and subsequently programming movements based on the context and individual needs/goals is the key to getting all of the goodness of plyometrics while remaining healthy and becoming resilient in the process.

Plyometrics Phase 1: Foundation

Phase one comprises of low-level, eccentric-focused movements that are geared toward individuals who are new to training, returning to training after a hiatus, and/or coming back from injury. For the most part, phase one isn’t so much about developing power, but rather about building a solid foundation in preparation for more advanced plyometrics that target power more specifically.

As a whole, the goal of phase one is three-fold: 1) establish the basic elements of motor control associated with jumping and landing, 2) ingrain proper landing mechanics and optimize force absorption with the muscles rather than the joints, and 3) build a foundation of eccentric strength.

#1 Squat Drop

While squat drops (also known as snap downs) may not be the most exciting exercise in the world, they can serve as a great starting point for introducing deceleration and ingraining solid landing mechanics in a controlled environment. Performed properly, they teach the coordination of smooth and sequential movement with jumping, landing, and force absorption

#2  Low Depth Drop

Low depth drops involve the same motion as squat drops, albeit with increased eccentric demands due to the low box step-off. The objective with low depth drops is to reinforce the ideal landing mechanics that were established during the squat drops while gradually building up eccentric strength.

 #3 Hop Series

Whereas squat drops and low depth drops are performed to hone in on the eccentric component of plyometrics, the rudiment hop series (as popularized by ALTIS) introduces the concentric action of jumping through low-impact, low-complexity hops. Regardless of the type, the purpose of hops is to increase tendon stiffness (i.e., “bounce”), strengthen the joints and connective tissue, and teach coordinated flexion and extension at the knees and hips in concert with relatively stiff ankles.

Variations: forward, backward, lateral, single-leg, left-left-right-right

#4 Static Box Jump

After establishing basic eccentric and concentric competency, static box jumps are the next step toward bridging the gap between a rapid takeoff and landing. Here, the purpose of the pause – the static component – is to encourage owning the bottom position while making it easier to jump and land with crisp mechanics (like a paused squat, in a sense). Static box jumps are also valuable for improving rate of force development, or power from a dead stop, which is especially beneficial for athletic performance.

#5 Box Jump

After static box jumps, standard box jumps (performed without a pause) are the first plyometric that involve a rapid countermovement prior to takeoff, which makes them the final stepping stone before moving onto phase two. Although social media may suggest otherwise, the purpose of the box isn’t to act as a target that tests how high you can lift your knees up next to your ears upon landing, but rather to reduce eccentric stress by shortening the distance of the descent. It’s not the height of the box that matters; it’s the powerful jumping action paired with a solid landing.

Variations: lateral, weighted, single-leg (with 1- or 2-leg landing)

Plyometrics Phase 2: Integration

Phase two is the integrative eccentric-to-concentric phase, meaning that it comprises of movements that combine the eccentric phase of landing (as established in phase one) with the concentric action of jumping through a countermovement. For most trainees, phase two is the sweet spot of lower body plyometric training as the movements within it are safe, effective, and versatile.

Overall, the goals of phase two are to build dynamic eccentric strength, further ingrain solid jumping and landing mechanics, introduce new starting/landing positions and additional planes, and continue to prepare the joints and connective tissue for increased eccentric demands.

#6 Seated Vertical Jump

In a sense, seated vertical jumps are a hybrid of static box jumps and box-less vertical jumps. Like static box jumps, the seated component makes them a concentric-focused movement with less risk of error. Without a box to land on, however, seated vertical jumps up the eccentric demands and, in doing so, prepare the joints and connective tissue for standing vertical jumps more directly.

Variations: rock-back, weighted

#7 Standing Vertical Jump

Like box jumps in the foundational phase, standing vertical jumps are the first plyometric of the integration phase to employ a rapid eccentric-to-concentric transition through a countermovement. What separates standing vertical jumps from box jumps, however, is their greater eccentric demands due to the increased distance of the descent.

Variations: multiple-response, weighted, hands on hips, single-leg (with 1- or 2-leg landing)

#8 Hurdle Jump with Mini-Bounce

As popularized by Mike Boyle Strength & Conditioning, hurdle jumps with a mini-bounce involve the creation and absorption of force in multiple planes (both vertically and horizontally), though only slightly and to a lesser extent than broad jumps. The purpose of the mini-bounce is to introduce a slight elastic/reactive component and bridge the gap between landing with a “stick” and landing with a shorter amortization phase, the latter of which is present in the more advanced plyometrics of phases 3 and 4.

Variations: lateral, single-leg (linear, lateral, medial)

#9 Broad Jump

What separates broad jumps from all of the preceding plyometrics is their max-effort horizontal focus. Since they require jumping (and landing) up and forward simultaneously, broad jumps require the body to create multi-planar force and withstand greater eccentric forces upon landing. For those who have built up the eccentric strength to perform them, broad jumps are a phenomenal movement for building horizontal power, which has a huge carryover to sprint speed – especially acceleration – for athletes.

Variations: multiple-response, single-leg, band-resisted

#10 Multi-Directional Jump Sequence

The multi-directional jump sequence as shown – or any multi-directional jump, really – combines several more advanced forms of progression: multi-planar force creation and absorption, increased eccentric demands, shorter ground contact times, and faster eccentric-to-concentric transitions between linear, lateral, and/or diagonal planes of motion. Given that being able to move outside of the sagittal plane is crucial for both life and sport, training multi-planar power via multiple-response (i.e., without resetting) and multi-directional jumping is essential for athletes and non-athletes alike.

Variations: endless combinations (e.g., vertical-to-broad, broad-to-lateral)

Plyometrics Phase 3: “True” Plyometrics

Phase three enters the realm of what many coaches classify as “true” plyometrics, as defined by an amortization phase lasting 0.2 seconds or less between the eccentric-isometric (force absorption) and concentric phase (force production). While the movements within it are undoubtedly intense, complex, and highly stimulating to the nervous system, they’re also a step above the preceding movements from a power development standpoint due to their utilization of the stretch-shortening cycle (SSC).

For the sake of simplicity, the SSC is the rubber-band-like effect that occurs in the muscles when an eccentric pre-stretch or counter movement is followed by a rapid shortening to produce faster and more powerful muscular contractions. Just as a rubber band travels further after it’s stretched out, so too do the muscles contract faster and with more force following a rapid stretch. As such, getting all of the goodness of the SSC requires bouncing out of the amortization phase in as short of a time period as possible.

#11 Approach Jump

Approach jumps, which are performed with a rapid three-step buildup, are more advanced than most of the preceding jumps due to their shorter ground contact times, added momentum, and the slight elastic element resulting from the pre-jump “bounce.” While the jury’s still out on whether or not approach jumps are true plyometrics, they’re nonetheless useful for transitioning from the aforementioned plyometrics to the more advanced progressions of phases 3 and 4. Beyond serving as a useful progression, approach jumps also have distinct value for specific populations – like basketball players, who employ similar pre-jump step sequences – while enabling higher jumps, to boot.

 #12 Continuous Suspension Assisted Jump

Fitting TRX/ring-assisted jumps into the regression-progression spectrum is tricky. On one hand, they take balance out of the equation and allow for more control. On the other hand, they utilize the arms to generate additional force and facilitate a rapid “bounce” off the ground when performed continuously (i.e., multiple-response), which leads to higher jumps and more intense landings. For those two reasons, assisted jumps can be valuable for either building elastic power in more advanced individuals, or as a regression for those who struggle with regular jumps.

Variations: single-leg, split squat stance (alternating/non-alternating)

#13 Depth Jump

Depth jumps are the most popular example of a “true” plyometric due to the fact that they involve a pre-jump drop followed by a short amortization phase and minimal ground contact time. More so than most jump variations, depth jumps harness all of the goodness of the SSC which – as mentioned previously – results in faster, more powerful muscular contractions following the SSC’s store-release sequence.

#14 Multi-Directional Depth Jump

Multi-directional depth jumps are like the multi-directional jumps of phase 2 in that they involve rapidly transitioning across multiple planes, albeit with the added element of the SSC due to the pre-jump drop. Since there’s no shortage of ways to implement them – whether it be linear, lateral, horizontal, single- or multiple-response, etc. – the beauty of multi-directional depth jumps is that they can be utilized to target a wide variety of power-boosting adaptations.

Variations: endless combinations (e.g., depth-to-lateral, depth-to-vertical-to-broad)

#15 Continuous Hurdle Jump

Continuous hurdle jumps are up there among the truest plyometrics for three reasons. First, depending on the height of the hurdles, they generally encourage near-maximal jump efforts that facilitate high amounts of force production, as well as significant eccentric stress upon landing. Second, they force the body to exert vertical and horizontal force simultaneously, both of which place increased demands on the muscles, joints, and tendonsto absorb multi-directional force. Third, they’re meant to be performed with minimal ground contact time – arguably even more so than depth jumps – which increases the intensity of the SSC and provokes a strong nervous system response.

Variations: lateral, single-leg (linear, lateral, medial)

Plyometrics Phase 4: Advanced Plyometrics

Phase four is the “anything goes” category, meaning there’s a handful of elements that can be added, increased, or mixed and matched to intensify both the demands as well as the power-reaping rewards of various plyometrics. Among other options, the movements within phase four can be progressed via added load, band resistance, banded overload, shortened ground contact times, multi-planar combinations, and more.

Like the movements in phase three, the movements in phase four are intense, complex, and highly stimulating, which means that not everyone needs to – or should, for that matter – force-feed it into their training. The key pre-requisites are sufficient strength, resilient joints and tendons, buttery smooth movement mechanics, and the ability to control load eccentrically and dynamically. Once earned, the movements within phase four can be used to build elite levels of lower body power.

#16 Weighted Jumps

While they aren’t fancy by any means, weighted jumps of all types – not just vertical jumps – are extremely effective for building lower body power, as they essentially overload the jump pattern while “tricking” the neuromuscular system into generating more force. The key is to find the loading sweet spot to maximize force (mass times acceleration) so that the added load doesn’t offset the speed of exertion too much.

Variations: multiple-response, vertical, broad, lateral, single-leg (1- or 2-leg landing)

#17 Trap Bar Jump 

Trap bar jumps are the king of loaded jumps. In comparison to barbell squat jumps – a commonly performed alternative – they’re not only more spine-friendly but also more effective for producing greater values in jump height, peak force, peak power, and peak rate of force development (1). They’ve also been shown to beat out unweighted vertical jumps for power production when 20% of 1-RM loads are used (2).

Variations: multiple-response, from hang position (standing)

#18 Band Assisted Jump

What separates band-assisted jumps from continuous ring/TRX-assisted jumps is the support provided by the bands, which adds two additional benefits. First, the band assistance increases the height of the concentric jumping action and provokes a strong neurological response that can enhance rate of force development. Second, it decreases the amount of time that’s spent on the ground in between foot contacts, which increases central nervous system firing rates and reduces inhibitory mechanisms within the neuromuscular system, ultimately resulting in increased takeoff velocities. For those who’ve earned the right to perform them, band-assisted jump training has been shown to produce significantly greater improvements in vertical jump performance than regular plyometric training alone (3).

Variations: single-leg (with 1- or 2-leg landing), split squat stance (alternating/non-alternating)

 #19 Band Resisted Jump

Band-resisted jumps are on the opposite end of the spectrum as band-assisted jumps, as the active band resistance increases the force needed to explode off the ground upon takeoff. As a result, band-resisted jumps improve lower body power through the same mechanism as weighted jumps – by “tricking” the neuromuscular system into generating more force – which ultimately creates long-lasting improvements in force production. It’s especially important to keep the volume low when performing band-resisted jumps due to the hard downward pull from the top.

Variations: multiple-response

#20 Weighted Depth Jump

Weighted depth jumps are the apex of lower body plyometrics – especially when performed multi-directionally and in combination with other jumps – as they amplify almost all of the aforementioned intensification techniques: minimal ground contact time, added load, high eccentric stress, multiple directions, usage of the SSC, etc.

Variations: endless combinations (e.g., depth-to-lateral, depth-to-vertical-to-broad)

plyometrics

Skips, Bounds, and Sprints

Aside from jumps, skips, bounds, and sprints also fit into the lower body plyometric category. Although they’re not as “training-specific” as jumps in terms of their direct carryover to training, they can be useful as part of the 6-phase warm-up on conditioning-focused days, or as part of a standalone speed training session.

Skips.  Skips, which are single-leg takeoffs followed by two foot contacts, are the simplest progression of the three options. A-skips are the most basic variation and can serve as a useful starting point for teaching coordination, rhythm, reciprocal patterning (i.e., synced up arm/leg action), and front-side running mechanics. Power skips for height and/or for distance are more advanced skip progressions that can have additional value for developing lower body locomotive power.

Bounds. Bounds are single-leg takeoffs followed by a single foot contact with the opposite leg. Due to the greater accelerative/decelerative forces that they impose on the body as well as their notably shorter ground contact times, bounds are generally considered to be more advanced than skips. Alternating bounds, single-leg bounds, and multi-directional bounds are the most common examples. 

Sprints. Although they’re often labeled as the “ultimate” lower body plyometric, sprints aren’t necessarily an uber-advanced activity that most individuals should stay away from. On the contrary, sprinting can be a phenomenal “exercise” for improving body composition, increasing full-body power, developing athleticism, and – when done for shorter distances – to cap off a 6-phase dynamic warm-up. Granted, it goes without saying that the key is to ensure that you or your clients/athletes are able to sprint pain-free; for those who can do so, however, sprinting can pay huge dividends for improving a multitude of qualities.

Plyometrics Practical Applications and Programming

There are five steps to determine which lower body plyometrics to perform, how to go about programming them, and when (or not) to move on to more advanced progressions:

  1. Assess you or your client/athlete’s starting point

Prior to programming and performing lower body plyometrics, factors such as injury/training history, strength levels, mechanical efficiency, movement pattern competency, and experience with plyometrics should be taken into account. If there are any red flags – whether someone is new to training, has certain contraindications, etc. – start conservatively and address any potential underlying issues separately. If you or your clients/athletes have trouble squatting or hinging, for example, start with phase one plyometrics and work on improving squat and hinge mechanics in the meantime.

  1. Select movements according to the starting point and individual needs/goals

For the vast majority of individuals who are mostly interested in looking, moving, and feeling better, the sagittal-focused movements within phases two and three should make up most of their lower body plyometric training. Other demographics, however – like athletes – often need to place a greater emphasis on single-leg, multi-planar, and more advanced movements due to the demands of their sports. For experienced trainees who are interested in throwing down dunks and boosting their 40-yard dash times, the movements within phase four can be game changers for building Olympian-esque power.

  1. Plug the chosen movement(s) into the 6-phase dynamic warm-up

The chosen plyometrics should be programmed into the tail end of the 6-phase dynamic warm-up based on the KPI lift of the day. For squat-focused days, vertical jumps are a perfect fit, whereas broad jumps and locomotive options (e.g., bounds) can work well prior to training the hinge pattern hard and heavy. Generally speaking, sagittal plane movements are the bread and butter of phase 6 plyometrics considering the sagittal nature of most KPI lifts, although multi-planar jumps can have their place depending on individual needs.

  1. Keep the intensity high, volume low, and prioritize quality over quantity

Maximal intent is the name of the game for maximizing the benefits of plyometrics, which means that excess fatigue should be avoided at all costs. From a programming standpoint, performing 2-4 sets of 3-5 reps with adequate rest is the sweet spot for ensuring maximal output, avoiding excess fatigue, and reaping all of the rewards of plyometric training.

  1. Determine what’s necessary and progress appropriately

The simplest way to gauge whether or not someone is ready to progress to more advanced plyometrics is to use the simple eye test. Can they perform the movements they’re currently doing pain-free? Are their jumping and landing mechanics smooth and crisp? Do the movements look athletic? If all the boxes are checked, a good rule of thumb is to increase the intensity slightly or throw in an added element of complexity.

It’s important to remember that, for some individuals, advanced progressions may not be necessary. Lower body plyometrics are a means to an end (training), not an end in and of themselves. At the end of the day, the two overarching goals of plyometrics – to develop power and prepare for training – are more important than any particular jump variation alone.

Still can’t jump? If you or your clients/athletes can’t perform plyometrics for whatever reason, seek out the help of a physical therapist and focus on joint-friendly alternatives in the meantime. Remember: the goal is to develop power and get to training, not to become a box jump hero at the expense of your health and well-being. Some good options are as follows:

  • Overcoming isometrics
  • Medicine ball throws/slams
  • Kettlebell swings
  • 1-arm DB/KB snatches
  • Sled sprints
  • Dynamic band work (e.g., pull-throughs, glute bridges)

Here’s To Smarter (Safer) Plyometrics

Although there’s no shortage of lower body plyometrics and a seemingly infinite number of ways to perform them, the overarching principles and methods of progression as mentioned are the key to implementing them safely and effectively. Like anything else in training, there’s no such thing as a one-size-fits-all approach to plyometrics, nor are there any mandatory movements needed to develop lower body power. Above all else, accounting for the context and individual needs/goals while keeping the purpose of plyometrics at the forefront – to develop lower body power and prepare for training – reigns supreme.

About The Author

charley gould

Charley Gould, CSCS, PPSC, CFSC, USAW

Charley is a former professional baseball player, current strength-and-conditioning coach, and writer for T-Nation and Bodybuilding.com. He specializes in helping individuals look, feel, and perform like elite athletes. Gould is the head of sports performance at Universal Athletic Club in Lancaster, Pennsylvania.

Follow Charley on CharleyGouldSC.com and Instagram

References

  1. Swinton, P. A., Stewart, A., Agouris, I., Keogh, J. W., & Lloyd, R. (2011). A biomechanical analysis of straight and hexagonal barbell deadlifts using submaximal loads. Journal of strength and conditioning research25(7), 2000–2009.
  1. Swinton, P. A., Stewart, A. D., Lloyd, R., Agouris, I., & Keogh, J. W. (2012). Effect of load positioning on the kinematics and kinetics of weighted vertical jumps. Journal of strength and conditioning research26(4), 906–913.

3.Imachi, I., S. Sasayama, and M. Man-I (1994). The Effect of suspension training in developing vertical jumping ability. J.J. Phys. Fit. Sports Med 43, no. 6 (1994): 703.