What is plyometric training for?

Plyometrics is defined as the exercises that enable a muscle to reach maximum force in a short period of time. Plyometric training is a series of explosive body weight resistance exercises using the stretch-shortening cycle (SSC) of the muscle fiber to enhance physical capacity such as speed, strength, and power. It is a quick, powerful movement involving pre-stretching the muscle tendon unit followed by a subsequent stronger concentric contraction. This process of muscle lengthening followed by rapid shortening during the SSC is integral to plyometric exercise. The SSC process significantly enhances the ability of the muscle-tendon unit to produce maximal force in the shortest amount of time. These benefits have prompted the use of plyometric exercise as a bridge between pure strength and sport-related power and speed. Plyometric exercise is a popular form of training used to improve athletic performance.[1][2]

Initially known as “Stretch Shortening Cycle” or “Jump Training” described by Russian national jump coach, Mr. Yuri Verkhoshansky.[3]

The term “Plyometrics” was coined by former athlete and American track and field coach, Mr. Fred Wilt.[3]

It is derived from the Greek word “Pliometric”. “Plio/Plythine” meaning more/increase and “Metric” meaning measurement. Thus meaning “to increase the measurement.”[3]

In this model, elastic energy is created in the series elastic component (SEC) of the muscle and tendon and stored as a result of rapid stretch.

This stored energy is then released when the stretch is followed immediately by a concentric muscle action by the concentric component(CC)such as actin, myosin and cross-bridges of the muscle contributing to the force production.[2]

This model is based on the concept of stretch reflex.

Stretch reflex is the body’s involuntary response to and external stimulus that stretches the muscle and the stretch receptors such as muscle spindle and golgi tendon organ.

When muscle spindle at the musculotendinous junction are stimulated, stretch reflex is seen.[2]

The SSC is a combination of both the models previously mentioned i.e the mechanical model and the neurophysiological model and it forms the basis of Plyometrics. It incorporates both, the storage of energy in the Series Elastic Complex (SEC) and the stimulation of the stretch reflex to facilitate maximum recruitment of muscle units in a short amount of time.

Stretch-shortening cycle consists of three phases:[4]

Lower Extremities:

Upper Extremities:

These are appropriate for virtually any athlete and any sport. Eg: Football, Basketball, Rugby, etc. The direction may vary from sport to sport, but most of them require the athletes the produce quick and maximal vertical or horizontal movements

Examples of lower extremity plyometrics:

These exercises are best suitable for sports that involves more of upper body demand. Eg. Cricket, Badminton, Tennis, etc.

Examples of upper limb plyometrics:

The core often plays a double role; one involving dynamic movement (provided by the outer core muscles) and the other providing strong static stability (provided by the inner core muscles). Thus these muscle groups also have to be trained along with the upper and lower extremity.

Examples of trunk plyometrics:

It is important to combine movements to better prepare athletes for the demand of their sports. A typical athlete may run, change directions, jump and throw a ball in a matter of seconds thus it is necessary to train these combination of movements in an athlete. These combinations not only produces significant results but it also makes the training session enjoyable.

Some examples of combination:

Plyometric intensity refers to the amount of stress placed on the muscles, connective tissue and joints. Initially the intensity of the plyometric exercises should be low. Gradual progression should be made in the intensity, complexity and the difficulty of the exercises.[5]

Factors affecting the intensity

Plyometrics exercises place a high demand on the athletes body thus adequate rest must be provided for the body to recover from the excessive load. Typical recovery time is between 48 to 72 hours. Thus the frequency of plyometrics training is two to four sessions per week.Each session should last for one hour which includes 15 minutes of warm up, 20 to 30 minutes of plyometric training and 15 minutes of cool down.[5]

For lower body the volume is measured by the number of contacts per workout session.Whereas for upper body, volume is expressed in number of throws/catches per session. As the training progresses the volume must be increased.[5]

Plyometrics is a form of resistance training thus the progression should follow principle of progressive overload.

The progression must be:

Currently, most of the  basic plyometrics program range from 4 weeks to 6 weeks. Advanced plyometric exercises program can range from 12 weeks to 18 weeks. During the advance phase, progression and combination of plyometrics with other training form should be done.[5][6]

Selection of plyometric training equipment must be done based on the type of exercise and the intensity. Equipment should be modifiable to suit the needs of individual athletes as no two athletes are the same.[6]

Examples of equipment:

The choice of training environment has a major impact on the effects of plyometrics exercise both in training specificity and injury prevention. The hardness of the surface can affect the amortization phase by increasing or decreasing the ground-contact time i.e., softer training surface causes higher contact time. On a softer surface the body stiffens whereas on a harder surface the body softens the connective tissue to absorb the impact and prevent injury. For athletes, It is advised to train on a relatively softer surface for major part of the training season to prevent soft tissue injury and maintain peak health during high-volume preparatory period.[6]

Some examples of training surfaces:

The choice of appropriate footwear for any training program can be critical in both performance and health.[6]

Functions of a footwear:

A good footwear should consists of:

When transitioning form early preparatory phase to pre-competitive phase the training must be carried out in the shoes that will be used for the sport. Eg: spikes for track and field athletes, cleats for soccer, rugby baseball players, court shoes for racket sports, basketball and volleyball, etc.[6]

Criteria to begin plyometric training:

Plyometrics is a form of intense training that involves the use of a stretch and contraction sequence of muscle fibers to generate great strength at a high speed. With this type of training session, you will improve your overall power and explosiveness.

Now, for some more details.

Plyometrics — plyos for short — is a type of exercise that trains muscles to produce power (strength + speed). Plyometric exercises involve a stretch of the muscles, immediately followed by a contraction of the same muscles — which is why it’s sometimes referred to as “jump training.”

While strength training mostly creates nervous system and muscular adaptations to get stronger,  plyometric exercises will help improve explosiveness — our ability to generate maximum force in a minimum time. Picture a sprinter taking off at the starting line, or an Olympic long jumper jumping from stillness, they both need explosive power to do what they do. Plyometrics is an important component of most professional sports performance training as it focuses on the “speed” component of power.

Plyometric exercises include vertical and broad jumps, where you jump as high and/or as far as possible. Skipping rope, jumping squats, single leg hopping and clapping push-ups are also great examples of plyometric exercises.

If you go to the gym, you probably noticed a few wooden boxes or metal platforms stacked beside other sports equipment. Plyometrics exercises often use these types of props to jump on and down from to promote a greater extension of muscle fibers.

Smart plyometric training will improve your speed and power, all while improving your coordination and agility too. With a smart and specific training plan, you can get faster when you sprint, jump higher during basketball games, change directions quickly on the soccer field or return tennis serves every time.

With that being said, plyometrics are a very high-intensity form of training that, yes, promotes speed and power, but also can lead to a greater risk of injuries. Plyometric exercises need to be executed with proper form, always respecting your body’s limits. Before adding the “jumping” and “explosiveness” component to the movement, first focus on perfecting squats before doing squat jumps onto a box or platform.

After perfecting the movements and adding the jumping, regular plyometric training with rest days in between will help maintain bone and joint health. Start slowly with two or three sessions per week with 24-48 hours in between.

What about clients seeking to improve general fitness? Power is essential for all three groups. By incorporating plyometric exercises into training programs, you can harness the speed and force of movement for improved performance and daily activities.

This content aligns with chapter 8 of the NASM Sports Performance Course.

Table of Contents

Plyometric training is a quick, powerful movement involving a system of reactive exercises and an eccentric contraction, followed immediately by an explosive concentric contraction. (1, 2) You accomplish this through any movement utilizing the Stretch-Shortening Cycle (SSC). (6, 7)

Plyometric training is often interchangeable with power training. However, as some traditionally use plyometric training to define a specific movement pattern in which three distinct phases of movement occur rapidly, not all power training is plyometric training (though all plyometric training is considered power training). Further, the movement patterns categorized in the NASM OPT Model's Phase 1 would better be classified as power patterns and not plyometric since they all involve a long pause (isometric) between the eccentric and concentric phases.

By contrast, Power Lifting is a sport and often confused with power/explosive training. To clarify, it is a misnomer as its primary focus is strength enhancement and development and traditionally does the bulk of training with heavy, slow lifts. Plyometrics is built upon various scientific principles (stretch-shortening cycle, optimizing sarcomere length, and stretch reflexes) that can help individuals tremendously boost their power output (2, 3).

Improvement to the Rate of Force Development and the maximum power output of various movement patterns related to sport is crucial to improving sport-related tasks. Still, it is also extremely valuable in return to play, post-rehabilitation, and pre-habilitation (or injury reduction) protocols. Note the following areas of injury reduction (3):

● Improved control for varus and valgus movements at the knees during landing● Enhanced dynamic knee stability during the deceleration phase of landing● Enhanced anaerobic power and vertical jump height● Improvement in overall power and change of direction speed in all planes of motion (saggital, frontal, and transverse)

Plyometric training can add a fun and challenging component to training programs. However, like most training protocols, it must be introduced, coached, and progressed systematically to avoid injuries.

Unilateral and gravity accelerated patterns such as bounding, hops, depth jumps, and combination jumps demand a solid foundation of stability, motor control, coordinated patterning, eccentric strength, joint integrity, flexibility, and technical proficiency to avoid injury.

Plyometric exercises have three distinct components: an eccentric, an amortization, and a concentric phase that releases the explosive force. These three components make up a stretch-shortening cycle.

During the eccentric component, the muscle is pre-stretched, storing potential energy in its elastic elements (2-7). The eccentric phase can be referred to as deceleration, absorption, loading, yielding, or the cocking phase (2-8).

When basketball players bend their knees and lower their arms before a rebound shot or when a baseball player pulls his arm back before a throw to first base are both examples of the eccentric component.

The amortization component is a time of dynamic stabilization during which the muscle transitions from overcoming the acceleration of gravity and loading the energy to releasing it. If this segment lasts too long, the potential elastic energy can be lost.

(Note: the value of the Non Countermovement or "Pause Jump" is seen here as the emphasis of the movement pattern can be placed upon pure RFD components and minimize the joint impact as well as elastic components). The shorter the amortization segment, the more powerful the results.

Unloading the elastic energy occurs next in the concentric phase, which adds to the tension generated in a concentric muscle contraction. This is where the athlete releases the stored and redirected energy, jumping for the basket or slinging the ball to first base.

Though the old adage of a client containing the prerequisite strength of squatting 1.5x bodyweight before the performance of plyometric patterns is overly simplistic and likely not applicable to all plyometrics patterns (i.e., upper body plyometrics), there are some relatively simple concepts we can use to ensure the success of our clients before adding these patterns to our programming for athletes and fitness enthusiasts.

Before incorporating plyometric exercises, athletes and clients alike must have the ability to balance efficiently and possess adequate core strength, joint stability, and range of motion. Plyometric drills may not be suitable for those with chronic or limiting conditions (2, 3).

Following the NASM Optimum Performance Training ™ (OPT™) model, plyometric exercises progress from Stabilization to Strength, then to Power (2, 3).

Plyometric exercises aren't limited to the lower body. There are upper-body activities, including plyometric push-ups, wall throws, overhead throws or combination moves such as a jump squat with a chest pass.

Of the many benefits of plyometric training, some of the more recognized are:

● increased vertical jump height● increased long jump distance● Increased strength● improved running speed, agility, and quickness● injury reduction● improved throwing, hitting, striking velocity

Why does the use of plyometrics and power patterns improve power output and performance? Several reasons have been found as to the realized benefits of utilizing plyometrics (1, 3, 6, 7):

● Rapid eccentric movement followed by immediate concentric contraction enhances power output 10-15%● Increased explosive strength due to improved rate of force development RFD● Increased reactive strength due to greater storage and re-utilization of elastic energy● Improved ability to transfer force through the joints and minimize energy leaks● Increased active state/force preload (pre-tension developed in anticipation of power output)● Enhanced Stretch Reflex (Muscle Spindle/greater contraction● Decreased co-contraction of the antagonist● Storage and re-utilization of elastic energy (series elastic component: tendon and aponeurosis)● Desensitization of the GTO● Enhanced neuromuscular efficiency

It's probably easier to see how plyometric training can improve athletic performance, but perhaps more challenging to see why plyometric exercises would benefit the non-athlete.

Plyometrics is interchangeably termed reactive training. From this perspective, it is essentially about how the body interacts with ground surfaces. Quickly responding to an unexpected change in the surface when stepping off a curb or rapidly changing direction when walking a dog on a leash are possible examples clients may encounter (2, 10).

Begin with activities that focus on plyometric stabilization exercises, even using regressions such as step-up/step-down or step-up/step-down to the front on a low box or bench.

You can later progress to jumping jacks, lunge jumps, or tuck jumps.

Recall that plyometric exercises are based on three components, an eccentric component that stretches the muscle, the amortization component focusing on dynamic stabilization, and the concentric component that concentrically contracts the muscle.

Many exercises are secretly plyometric exercises if they incorporate explosive moves. Progress plyometric exercises safely by going from easy to challenging, simple to complex, known to unknown, stable to unstable, bodyweight to loaded, or activity-specific (2, 3).

Plyometric programs are generally developed and progressed consistent with movement complexity, skill-level or mastery, the plane of movement, exercise progression choice, but most importantly, volume and intensity.

The number of foot contacts determines volume (e.g., each time you land or catch = 1 contact) or upper-extremity contacts completed (e.g., each time you catch a ball = 1 contact) (See Table 1-1).

The plyometric activity's intensity is primarily related to variables such as the amount of acceleration due to gravity placed on the body, the amount of impact, whether the pattern is bilateral or unilateral, and what complexity is built into the pattern.

Important to note that while early texts were proponents of higher volume (80-200 contacts seen in table 1-1) (4, 5), more current texts tend to favor reduced volume (25-50 contacts)(1, 3, 6, 7) and place greater emphasis on intensity of patterns as well as the specificity to the sport of the patterns to reflect gameplay.

Historically, much of the research done strictly on plyometric training and outcomes has been done to exclude other training modes (i.e., strength training). Thus much of the recommendations based on research have often been higher in volume as it has not factored in other mixed modes of training. (6)

An integrated strength and conditioning program should encompass, there is simply not enough time to perform high volumes of plyometric and power work if everything is to be addressed in a 60 - 90 minute session with 2-4 sessions per week. Further, it can be argued that to maximize neural and elastic components of power/plyometric training. Volumes should be kept lower to optimize rest and intensity efforts as it is for loaded power and strength efforts (i.e., Olympic Lifting and Barbell Squatting) (1, 3, 6, 7, 8)

Adapted from Guide to Real Jump Training (8)

Regardless, training good form with inexperienced individuals or allowing adequate dynamic warm-up with more experienced individuals to reinforce good mechanics are critical to success and avoiding injury.

When designing plyometric programs, as long as the volumes and intensities align with the OPT recommendations, planning can allow for jump and power training 2-4 days per week to maximize learning, progress, and address all planes vectors necessary for integrated performance enhancement.

Use lower-intensity drills (e.g., jumps-in-place, single linear jumps like one plyo box jump) and moderate intensity-drills (multi-directional jumps or multiple linear jumps like a continuous set of plyo box jumps for 10 seconds) as part of your warm-up or as exercises more frequently throughout the week.[1]

Teaching good technique begins with instructing landing/absorbing/catching mechanics and progressing the program only when form mastery is exhibited.

Some simple mantras to remember are that you must "Load before you can explode" and "train slow, move slow, train fast, move fast, but if you can't do it slowly, you can't do it fast." Some coaching tips to improve jump-landing mechanics include:

Body position and mechanics, as well as landing/absorption, is key in this phase. (1, 3, 8)

● Instructing individuals how to properly hip-hinge and land is critical. From a standing position, using a dowel or light bar and maintaining good spinal orientation as the body hinges and lowers (i.e., 3 points of contact with the bar – sacrum, thoracic spine, and back of the head) can be helpful. This movement, versus a more quad-dominant lowering position, reduces knee and hip shearing forces while also loading (eccentrically) the gluteus maximus to facilitate more powerful unloading (concentric contraction) during the triple extension phase (ankle, knee, and hip).

● Further, athletes must be instructed about ground contact and absorption. Keeping it simple, since the priority is force absorption to reduce impact and joint wear and tear, the cues keep it quiet and keep it soft. The less noise/sound on impact, the better. A standard error is the "heel slap."

This is the inability (or lack of awareness/effort) to keep the heel of the foot from striking/impacting the ground hard and causing a loud noise on the landing. This increases impact forces. If this cannot be controlled, the pattern's intensity should be reduced until the athlete can master the ability to quietly land on the fall of the foot and maintain a credit card space underneath the heel.

● Arm swing must be taught and not overlooked. It is key to potentiating power and is often misunderstood by athletes. Arms need to be loaded back in hyperextension early and released into flexion with maximal effort.

● LPHC-knee-toe alignment is vital. Getting athletes to keep these priority segments aligned in the sagittal plane (allowing for hip- shoulder-width foot placement based on jumps) has been shown to decrease injury and improve force production due to less lost energy or force leaks.

● Emphasize upper extremity alignment and head position (eyes-ups, head aligned with the spine) using cues like nose-over-toes or chest-over-knees at the bottom of the eccentric loading phase.

● Keep the patterns primarily uniplanar and directional in this phase.

Introduce more dynamic movements, which will begin to vary planes and directions and increase gravity acceleration and impact forces. (1, 2, 3, 6, 7, 8)

● Introduce two planes or direction of movement into patterns

● The introduction of barriers to jump over and variable planes and increased movement speeds due to gravity and countermovement patterning will challenge the athlete to gain another level of motor control and absorption and the ability to change direction and release the stored energy to a greater degree.

● When ready, begin coaching your athletes to reduce the amortization phase or transition between the lowering and rising phases to harness elastic energy into motion (minimizing potential energy leaks).

● Maintain all postural and landing considerations from previous phases.

Progress to double contact movements/bounces (small jump preceding large jump) to potentiate the SSC further. This is what most consider "true plyometrics," wherein the emphasis is on switching from a landing (eccentric) to a take-off (concentric) as rapidly as possible. (1, 2, 3, 6, 7, 8)

● Introduction of bounce or double contact.

● Emphasize minimizing ground contact time.

● Maintain all postural and landing considerations from previous phases.

● Introduce alternating limb patterns.

● Introduce 2+ planes and/or directions of movement.

● Introduce external load.

The focus of this phase is to move the full spectrum of velocities, planes, directions, and sport-related patterns to fully integrate the weight room to the playing field (1, 2, 3, 6, 7, 8)

● Introduce multiple loading variable and skills into sequences (i.e., MB throws to barrier jumps to sprints.)

● Introduce repeating patterns with maximal elasticity demands (depth jumps, high hurdle jumps, etc.)

● Introduce reactive/chaotic scenarios.

● Hybrid variations of takeoffs and landings (1 - 2 leg and 2 - 1 leg.)

In closing, while plyometrics can be fun, take the needed time to prepare the body physiologically. Develop your systematic plan to advance individuals towards higher-intensity drills once they demonstrate technique mastery and adequately tolerate jump-landing forces.

EXAMPLE PROGRAMS:

4 days/week Program:

● Focus:

○ Landing○ NCM Movement○ Minimal Gravity acceleration○ Single plane/direction patterns

Basketball: Phase 2 Strength Endurance

● Focus:

○ Transition from landing to take off○ CM Movement○ Increased gravity acceleration○ Multiple plane/direction patterns

Basketball: Phase 3 Muscular Development

Basketball: Phase 4 Max Strength

Basketball: Phase 5 Power

Boyle, M. New Functional Training for Sports, 2nd ed. Champaign, IL. Human Kinetics; 2016.Clark, MA, et al. NASM Essentials of Personal Fitness Training 6th ed. Burlington, MA. Jones & Bartlett Learning; 2018.

McGill, EA, Montel, I. NASM Essentials of Sports Performance Training, 2nd Edition. Burlington, MA. Jones & Bartlett Learning; 2019.

Chu, DA. Jumping Into Plyometrics 2nd ed. Champaign, IL: Human Kinetics; 1998.

Chu, D and Myers, GD. Plyometrics: Dynamic Strength and Explosive Power. Champaign, IL. Human Kinetics (2013).

EXOS Phase 1 Performance Mentorship manual.

EXOS Phase 3 Performance Mentorship manual. San Diego. July 27-30, 2015

Feit, A. Developing the Total Athlete Video Series: Guide to Real World Jumping [Video file]. Retrieved from https://athletesacceleration.com/dta-power/

Plyometrics is a type of exercise training that uses speed and force of different movements to build muscle power. Plyometrics training can improve your physical performance and ability to do different activities.