Definition[edit | edit source]
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 fibre to enhance physical capacity such as increasing musculotendinous stiffness 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.
History of Plyometrics[edit | edit source]
Initially known as “Stretch Shortening Cycle” or “Jump Training” described by Russian national jump coach, Mr. Yuri Verkhoshansky.
The term “Plyometrics” was coined by former athlete and American track and field coach, Mr. Fred Wilt.
It is derived from the Greek word “Pliometric”. “Plio/Plythine” meaning more/increase and “Metric” meaning measurement. Thus meaning “to increase the measurement.”
Models of Plyometrics[edit | edit source]
Mechanical Model[edit | edit source]
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. 
Neurophysiological Model[edit | edit source]
This model is based on the concept of stretch reflex.
Stretch reflex is the body’s involuntary response to an external stimulus that stretches the muscle and the stretch receptors. Stretching of the muscle spindles causes a reflex contraction of the stretched muscle. Additionally, Golgi Tendon Organs inhibit the muscle action if the muscle tension increases.
Stretch Shortening Cycle[edit | edit source]
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:
Eccentric Phase (Loading Phase)[edit | edit source]
- Pre-stretch of the agonist muscle.
- Elastic energy is stored in the SEC.
- Muscle spindles are stimulated.
Amortization Phase (Coupling Phase)[edit | edit source]
- It is the time between the end of pre-stretch and the start of concentric muscle action.
- Pause between phase 1 and 3.
- Type 1a afferent nerve fibres from the muscle spindle synapse with alpha motor neuron.
- Ideal coupling phase lasts for 15 milliseconds.
Concentric Phase (Unloading Phase)[edit | edit source]
- Shortening of muscle fibres.
- Elastic energy is released from the SEC.
- Alpha motor neurons stimulate the agonist muscle group.
Indications[edit | edit source]
- To maintain high level of functional activity.
- To improve balance and proprioception.
- To increase muscle strength and power.
- To maximize reaction time.
- to maximize efficiency of movements.
Contraindications[edit | edit source]
- Unconditioned athlete - lack of foundational strength and training.
- Unyielding surface.
- Stress related injury history.
- Acute or sub-acute sprains.
- Acute inflammation.
- Post-operative condition.
- Joint instability.
Ideal Plyometrics Training Program[edit | edit source]
Targeted Muscle Groups[edit | edit source]
- Gluteal muscle group.
- Hip flexor group.
- Quadriceps muscle group.
- Hamstring muscle group.
- Anterior tibialis.
- Rotator cuff muscles.
- Scapular stabilizers.
- Latissimus dorsi.
- Spinal erector muscle group.
Mode[edit | edit source]
Lower Body Plyometrics[edit | edit source]
These are appropriate for virtually any athlete and any sport. E.g.,: Football, Basketball, Rugby, etc. The direction may vary from sport to sport, but most of them require the athletes to produce quick and maximal vertical or horizontal movements. These are usually exercises involving jumping, bounding or hopping. 
Examples of lower extremity plyometrics:
- Jumping in place.
- Box drills.
- Drop jumps.
Upper Body Plyometrics[edit | edit source]
These exercises are best suitable for sports that involves more of upper body demand. Eg. Cricket, Badminton, Tennis, etc.
Examples of upper limb plyometrics:
- Ball throws.
- Kettle bell swing.
- Ball catches.
- Push ups.
Trunk Plyometrics[edit | edit source]
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:
- Russian twists.
- Seated medicine ball pass.
- Standing rotational ball pass.
- Prone push pass.
Combination Plyometrics Exercise[edit | edit source]
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:
- Combining variety of jumps.
- Jump and throw.
- Throw and sprint.
- Jump and sprint.
- Jump and throw, etc.
- (Be creative).
Intensity[edit | edit source]
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.
Factors affecting the intensity
- Body weight.
- Point of contact.
- Height of the drill.
Frequency and duration[edit | edit source]
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 three 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.
Volume[edit | edit source]
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.
Progression[edit | edit source]
Plyometrics is a form of resistance training thus the progression should follow principle of progressive overload.
The progression should be:
- Bilateral to unilateral.
- Stable to unstable.
- Symmetric to unsymmetrical.
- Simple to complex.
- Low intensity to high intensity.
- Combination of movements.
- Change of surface.
- Add barriers (such as cones, hurdles, boxes, etc).
Program length[edit | edit source]
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.
Equipment, surfaces and footwear.[edit | edit source]
Equipment[edit | edit source]
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.
Examples of equipment:
- Plyometric boxes.
- Medicine balls.
- Barbells/dumbbells/kettle bells.
- Resistance bands.
- Weighted vests.
Surfaces[edit | edit source]
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.
Some examples of training surfaces:
- Artificial turf.
- Indoor wooden courts.
- Rubberized track and flooring.
Footwear[edit | edit source]
The choice of appropriate footwear for any training program can be critical in both performance and health.
Functions of a footwear:
- Protect the feet from daily wear and tear.
- Deliver impact that produces strides, jump, change in direction.
- Sensory feedback.
- Shock absorption.
A good footwear should consists of:
- Proper covering of the foot.
- Proper cushioning.
- Thicker heel.
- Good ankle stability.
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.
Safety and pre-training considerations[edit | edit source]
Pre training considerations[edit | edit source]
Criteria to begin plyometric training:
- Strength: 80% to 85% of strength / MMT OF 4/5 for injured muscles and 5/5 for all other muscles.
- Range: 90% to 95% of range of motion.
- Load: Initial load must be 30% of 1 RM.
- Speed: Drills must be performed quickly but safely.
- Rate: The rate of stretch is more important than the length of stretch.
- Frequency: Plyometrics should not be performed more than 4 times a week.
- Intensity: When intensity is high volume should be reduced.
- Body awareness: Coordination, balance, body control.
Safety[edit | edit source]
- Evaluate the athlete thoroughly.
- Ensure the facility, environment and equipment are safe.
- Establish sports specific goals.
- Teach the athlete proper technique.
- Always perform the exercises under supervision.
- Proper progression of the program.
- soccer specific plyometric training program.
Conclusion[edit | edit source]
- In conclusion, Plyometric training is a series of explosive body weight resistance exercises.
- Based oh stretch shortening cycle which consists of three phases; eccentric contraction, amortization and concentric contraction.
- Plyometric training can be done for the upper extremity, lower extremity and the trunk.
- Adequate recovery time must be provided.
- Sports specific program design should be developed.
- Training should be done on appropriate surface with proper footwear and equipment.
- Precautions must be taken for the safety of the athlete.
References[edit | edit source]
- Dick FW. Sports training principles: an introduction to sport science [Internet]. Bloomsbury Sport. 2014 [cited 2023 May 19]
- Zatsiorsky VM., Kraemer WJ., Fry AC. Science and Practice of Strength Training [Internet]. Human Kinetics. 2020 [cited 2023 May 19].
- Chmielewski TL, Myer GD, Kauffman D, Tillman SM. Plyometric exercise in the rehabilitation of athletes: Physiological responses and clinical application. J Orthop Sports Phys Ther. 2006;36(5):308-319.
- The Movement System. Plyometric Training Explained. Available from: https://www.youtube.com/watch?v=4VodW4pW0Ic [last accessed 18/05/2023]
- Flom, Cynthia K., "Plyometrics" (1993). Physical Therapy Scholarly Projects. 145.
- Chmielewski TL, Myer GD, Kauffman D, Tillman SM. Plyometric exercise in the rehabilitation of athletes: physiological responses and clinical application. J Orthop Sports Phys Ther. 2006 May;36(5):308-19
- Chu DA., Meyer GC., Plyometrics [Internet]. Human Kinetics. 2013 [cited 2023 May 19]
- The Movement System. Stretch Shortening Cycle Explained | Physiology and Training the SSC. Available from: https://youtube.com/watch?v=iilyVw5uVXg [last accessed 19/05/2023]
- Davies G, Riemann BL, Manske R. Current concepts of plyometric exercise. Int J Sports Phys Ther. 2015 Nov;10(6):760-86.