|Year : 2015 | Volume
| Issue : 1 | Page : 20-25
Lower quarter plyometric for soccer players
Umair Anwer, Shibili Nuhmani
Department of Rehabilitation Sciences, Hamdard University, New Delhi, India
|Date of Web Publication||19-Jan-2015|
Department of Rehabilitation Sciences, Hamdard Institute of Medical Sciences, Hamdard University, New Delhi
Plyometric is a type exercise training to produce fast, powerful movements and improves performance in sports. It is used to increase speed or force of muscular contractions, providing explosiveness in sport-specific activities. Plyometric is a type of explosive exercise which is used in soccer, basketball, boxing, parkour, American football and rugby, gymnastics, volleyball, racket sports, martial arts, professional cycling, athletics (including track and field events). It contains the prerequisites consisting of the biomechanical examination, which is helpful in finding out stable base of support and normal force transmission, stability testing, which is divided into two parts-static stability and dynamic movement testing, and flexibility that start with general flexibility exercises. Plyometric program design contains the four variables-intensity, volume, frequency, recovery which are interlinked with each other in training the sportsperson in each session. Phases of plyometric are divided into three parts, which consist of the loading phase, the coupling phase and the unloading phase. And finally when specifying the soccer specific plyometric training the physiotherapist should keep in mind that the sportsperson being trained should go for warm-up producing mild sweating. Later approaching toward the specific types of jumps, including traffic cones of defined height and jumps excluding the cones. The jumps that are included within the programme would be double leg side jump, single-leg side jump, turning cone jump, squat jump, rocket jump, power skipping, lateral bound, knee tuck jump, multiple jumps with a sprint.
اثر تدريب بليومترى فى لاعبي كرة القدم - مقال استعراضى
تدريب بليومترك (Plyometric) هو نوع تدريبات لإحداث نتاج حركات قوية فى فترات قصيرة ذلك من اجل تحسين الأداء عند ممارسة الرياضة. وهذا النوع من التدريب يزيد قوة انقباض العضلات مما ينتج الانفجارية اثناء ممارسة بعض الرياضات مثل كرة القدم، كرة السلة ، الملاكمة ، الباركور ، وكرة القدم الأمريكية و الرجبي ، والجمباز ، الكرة الطائرة ،رياضات المضرب ، فنون الدفاع عن النفس، وركوب الدراجات، وألعاب القوى (بما في ذلك سباقات المضمار والميدان ). ومن المتطلبات الأساسية لهذا النوع من التدريب الفحص الطبى والمخبرى النشاط الحيوي ، وهو أمر مفيد في معرفة قاعدة مستقرة من الدعم و انتقال القوة العادي ، واختبار الاستقرار ، الذي ينقسم إلى قسمين ساكنة الاستقرار و ديناميكية اختبار الحركة، والمرونة التي تبدأ مع تمارين المرونة العامة. ان تصميم البرامج لتدريب تدريب بليومترك (Plyometric) يحتوي على أربعة متغيرات: الشدة والحجم والتردد، والانتعاش وجميع المتغيرات مترابطة مع بعضها البعض اثناء تدريب الرياضي. وتنقسم مراحل plyometric إلى ثلاثة أجزاء ، والتي تتكون من مرحلة التحميل، مرحلة اقتران و مرحلة التفريغ. و أخيرا عند تحديد plyometric خاص بلكرة القدم يجب على أخصائي العلاج الطبيعي أن يضع في اعتباره البداية بالاحماء حتى درجة التعرق الخفيف. وفي وقت لاحق الوصول الى الأنواع معينة من القفزات ، بما في ذلك الأقماع المرورية ذات الارتفاع المحدد و يقفز بعيدا عن المخاريط . اما نوع القفز التى يجب تضمينه ضمن البرنامج يراعى فيه ان يتم القفز بالساقين قفزا لجانبيا ، أوحيد بساق واح، و الدوار حول مخروط الوثب ، والقفز القرفصاء ، والقفز الصواريخ ، الجانبي المربوط والركبة الثنية القفز، يقفز متعددة مع العدو.
Keywords: Cone jump, jump height, stretch reflex
|How to cite this article:|
Anwer U, Nuhmani S. Lower quarter plyometric for soccer players. Saudi J Sports Med 2015;15:20-5
| Introduction|| |
Plyometric training was introduced by Dr. Yuri Verkhoshansky in Russia that was then called as "Shock training."  This led to the creation of the two true plyometric exercises called as depth jumps and depth drops. This principle only stays true for depth jumps and depth drops. It is perfectly safe to perform low to moderate intensity plyometric such as ankle hops or rim jumps even if your squat is not 1.5 times your bodyweight. Plyometric training increases the amount of force an athlete can produce. It leads to improved sports performance, a high vertical leap, and faster sprinting times.
The term "PLYOMETRICS" was coined by American track and field coach, Fred Wilt. A plyometric contraction involves first a rapid muscle lengthening movement (eccentric phase), followed by a short resting phase (amortization phase), then an explosive muscle shortening movement (concentric phase), which enables muscles to work together in doing a particular motion.  The purpose of plyometric is to emphasize speed based power. One activity that requires speed favoured power is high jumping. Ultimately, jump height is determined by how fast one is moving once his legs have left the ground. Basically, plyometric relies on an element of physiology called the stretch-shorten cycle (SSC). The SSC means that the muscle is rapidly stretched and then contracted which increases the force applied on the muscle.
| Prerequisites of plyometric|| |
Before beginning a plyometric training program, a biomechanical examination should be performed to find out any potential contraindications or precaution. Lower quarter biomechanics is helpful in finding out stable base of support and normal force transmission. Lower quarter biomechanical abnormalities are not contraindications for plyometric but may contribute to stress failure. Before starting plyometric training, an adequate amount of strength must be present. Functional tests are very effective to look for adequate strength before initiating plyometric. Poor strength in the lower extremities will give the result to the loss of stress that is absorbed weight bearing tissues with high impact forces, which will reduce performance and increase the risk of injury. The eastern block countries arbitrarily placed one repetition in which the individual had to lift at least 1.5-2 times of his own body weight in squatting before initiating lower quarter plyometrics.  Clinical and practical experience has demonstrated that plyometric can be started without that kind of leg strength. A simple functional parameter to use in determining if an individual is strong enough to initiate a plyometric training program has been advocated by Chu. Plyometric training program designed by Chu in which the athlete is asked to perform five squat repetitions in 5 s and if he fails to do so, he goes for strength-training program in his lower quarter.
| Stability testing|| |
Stability testing before initiating plyometric training can be divided into two subcategories: static stability testing determines the individual's ability to stabilize and control the body. The muscles of postural support must be strong enough to withstand the stress of explosive training. Static stability testing should begin with simple movements of low motor complexity and progress to more difficult high motor skills.  The basis of lower quarter stability centres around single-leg strength. Difficulty can be increased by commanding the individual to perform same with eyes closed. The basic static tests are one-leg standing and single-leg quarter squats that are held for 30 s with eyes open and eyes closed before starting plyometric training. The individual must be checked for shaking or wobbling of the extremity joints. If weakness is determined, the individual's program should be limited and emphasis placed on isolated strengthening of the weak muscles.
- Single-leg stance - 30 s
- Eyes open
- Eyes closed
- Single-leg 25% squat - 30 s
- Eyes open
- Eyes closed
- Single-leg 50% squat - 30 s
- Eyes open
- Eyes closed.
Dynamic movement testing
Dynamic movement testing will assess the individual's ability to produce explosive, coordinated movement. Vertical or single-leg jumping for distance can be used for a lower quarter. The investigation as done by Rus Paine and Dr. David Drez included the twice testing of the involved leg, and the average between the two trials is recorded. The noninvolved leg was tested in the same fashion, and then the scores of the noninvolved leg are divided by the scores of the involved leg and multiplied by 100. This provided the symmetry index score. Another functional test, which is makes an individual ready for plyometric training is to long jump the distance equal the height of the individual.
General and specific flexibility is one of the prerequisite for plyometric training. All plyometric trainings should start with the general warm-up and flexibility exercise program, and it should produce mild sweating. The flexibility exercise program should take care of muscle groups involved in the plyometric program including static and short term dynamic stretching techniques.  when an individual can demonstrate static and dynamic control of their body weight with single-leg squats, low-intensity in-place plyometric can be initiated. Plyometric training should consist of low-frequency drills and progress in a deliberate fashion. Mature athletes with strong weight - training backgrounds can be introduced to ballistic-reactive plyometric exercises of high intensity. Once an individual has been classified into the category of either a beginner, intermediate or advance level, the plyometric program can be planned and initiated. Chu has divided lower quarter plyometric training into six categories. 
Chu's plyometric categories:
- In place jumping
- Standing jumps
- Multiple response jumps and hops
- In-depth jumping and box drills
- High stress sport-specific drills.
| Neurophysiology of plyometric|| |
The proprioceptive stretch reflex is the mechanism by which force can be produced during the stretch-shortening cycle. Mechanoreceptors located within the muscles provide the information about the degree of muscular stretch. This information is transmitted to the central nervous system and becomes capable of influencing muscle tone, motor execution programs, and kinetic awareness. The mechanoreceptors that are primarily responsible for the stretch reflex are the Golgi tendon organs and muscle spindles.  The muscle spindle is the complex reflex receptor that is located in parallel within the muscle fibers.
When the muscle spindle becomes stretched, and afferent sensory response is produced and transmitted to the central nervous system. Neurological impulses are in turn sent back to the muscle, causing the motor response. As the muscle contracts, the stretch on the muscle spindle is relieved, thereby removing the original stimulus. The strength of the muscle spindle response is determined by the rate of stretch. 
The increased force production seen during the stretch-shortening cycle is due to combined effects of storage of elastic energy and the myotatic reflex activation of the muscle.  the increased amount of force production is dependent on the time frame between the eccentric and concentric contractions. 
| Plyometric program design|| |
It is defined as the amount of effort exerted. By the use of plyometric training, intensity can be controlled by the type of exercise that is performed. Double leg jumping is less stressful than the single-leg jumping. With the functional exercise, the plyometric exercise program progresses from simple to complex activities. Intensity can further be increased by altering the exercises, by adding external weight or by increasing the height of the step or box will increase the exercise intensity. 
Volume is the total amount of work performed during single workout session. Volume of plyometric training is measured by counting the total number of foot contacts. Foot contacts vary inversely with the intensity of the exercise in any one session. For a beginner, it starts with low-intensity exercise with the volume of 75-100 foot contacts. As the ability is increased, the volume is increased to 200-250 foot contacts of low-to-moderate intensity.
Frequency is the number of times that an exercise session is performed during a training cycle. It is suggested that 48-72 h of rest are necessary for full recovery before the next training stimulus.  Intensity however plays a major role in determining the frequency of training. If an adequate recovery period does not occur, muscle fatigue will result in a corresponding in neuromuscular reaction times. The beginner should allow at least 48 h between training sessions.
| Recovery|| |
Recovery is the rest time used between the exercise sets. Manipulation of this variable depends on whether to achieve increased power or muscular endurance. Since plyometric is anaerobic in nature, a longer recovery period should be used. In the power training, a work rest ratio of 1:3 or 1:4 should be used.
For endurance training, this work-rest ratio can be shortened to 1:1 or 1:2. Endurance training usually uses circuit training in which the individual moves from one exercise set to another with a minimum amount of rest time in between.
| Phases of plyometric|| |
The first phase of the plyometric movement can be classified as the loading phase. This phase has also been called an eccentric, deceleration, yielding, counter movement or cocking phase.  in this phase of plyometric exercise the muscle-tendon units of the prime movers and synergists, which in the lower extremity are typically the antigravity muscles, are stretched as the result of kinetic energy or loading applied to the joint. The kinetic energy may come from the preceding jump, from an external source, such as an approaching medicine ball, or from the concentric action of the antagonistic muscle group (countermovement).
Stretching of the muscle-tendon unit during the loading phase elicits the stretch-shortening cycle, which results in enhanced force production and performance when compared to the absence of stretch.  The loading phase begins when the muscle-tendon units begin to perform negative work.  Termination of the loading phase has been variably defined. Studies that consider movement of the entire body use the time point in which the centre of mass reaches its lowest position, velocity of the centre of mass reduces to zero, or the ground reaction force (GRF), curve begins to reverse direction.  Because multiple joints are involved in whole body movements, such as jumping, and because the joints are likely to undergo different timing and amplitudes of angular changes, delineation of the loading phase by a combination of GRF and individual joint angular velocity may allow for a more specific application and understanding of the mechanisms involved at a particular joint.
Stretch of active muscle during the loading phase elicits two mechanisms associated with the stretch-shortening cycle: muscle "potentiation" and the stretch reflex.  Muscle potentiation is an alteration of the muscle contractile properties that leads to higher force production. 
Data suggest that stretch reflex may not be elicited in all muscles that are stretched during a plyometric activity. Rather the muscle response is dependent on the number of joints that are crossed and the specific activity.
Signals generated by muscle stretch are called length feedback and those generated by muscle force are called force feedback. Length feedback, which occurs around the same timeframe as the stretch reflex, links muscles that are synergists through excitatory feedback and those with opposite actions by reciprocal inhibition.  Length feedback also links monoarticular muscles, like the vastus lateralis and soleus, with excitatory feedback. Force feedback, which is provided by stimulation of the golgi tendon organ, connects muscles that cross different joints and exert torque in different directions through inhibitory feedback. 
The time between the loading and unloading phase of a plyometric exercise is the coupling phase. This phase is commonly known as the amortization phase and also called as transmission phase.  The coupling phase is generally a period of quasi-isometric muscle action, and movement variables are often used to define the beginning and end of the coupling phase.  For the most part, muscle fascicle length does not change at the time when the joint angle, vertical GRF, or center of mass of the body is about to change the direction. Studies of the medial gastrocnemius muscle during sagittal plane ankle movements in standing or supine confirm that the muscle fascicle length is relatively stable, or reaches a transition between lengthening and shortening, at the time when the joint angle and the vertical GRF changes direction.  Similarly, during drop jumps performed on a sledge apparatus, the vastus lateralis muscle fascicle length is relatively stable or reaches a transition between lengthening and shortening, at the time when the joint angle and the vertical GRF change direction. 
The unloading phase of a plyometric exercise occurs immediately after the coupling phase and involves shortening of the muscle-tendon unit.  This phase has also been called the rebound, shortening, push-off or propulsion phase. For a single lower extremity joint, the unloading phase has been defined as beginning when the joint angle curve reverses direction and ending when the GRF goes to zero, or beginning when the muscle-tendon unit begins to shorten and to end at toe-off.  The unloading phase is considered the payoff or resultant phase, as this portion of the plyometric activity is when the mechanisms elicited during the loading phase contribute to increased efficiency of force production. Data suggest that improved efficiency isolated mechanism; rather, performance enhancement from plyometric activity is acquired from the summation of storage and reutilization of elastic energy,  muscle potentiation,  and the contribution of the myotatic stretch reflex.
| Soccer specific plyometrics|| |
To get your soccer player ready for plyometric, a normal soccer warm-up (running, stretching, etc.) should be done. 
Soccer requires a tremendous amount of explosive lateral movements. Cone jumps are a way of incorporating explosive jumping with lateral movement. Plastic traffic cones of various sizes are perfect for these drills. Plastic cones provide a safe obstacle over which your athlete can jump.
Double-leg side jumps
The athlete simply performs side to side jumps over a cone. The cone forces the athlete to jump up while moving laterally. Use cones of different heights. If you want to emphasize speed, use smaller cones. For the power, use taller cones. In any case the athlete should be able to clear the height of the cone. 
Single-leg side jumps
These jumps are similar to double leg jumps, except that the athlete jumps from one foot to the other. When teaching this drill, make sure that a player drives the knee of the free leg up while jumping. This keeps the athlete from merely falling from one foot to another. 
Turning cone jumps
Have the athlete jump from side to side while making half turns (180°). This helps develop the ability to make explosive reversals of direction. Now have your athlete jump from side to side over the cones while moving forward. The drill can be done as a double leg or single-leg drill. 
From a relaxed upright stance, feet shoulder width apart. Place the hands at the back of the head. Begin by flexing downwards to a half squat-position; immediately stop the downward movement and explode upward as much as possible, extending (straightening out) hip, knee and ankle joints, to full length, as quickly as u can. On landing, your hip, knee and ankle should already be flexed. During multiple jumps, the jump phase exercise should be started before reaching the semi squat-position. 
A relaxed upright stance, feet shoulder width apart. Slightly flex the arms and hold them close to the body. Begin by flexing downwards to a half-squat-position; immediately stop the downward movement and explode upward as high as possible, extending (straightening out) the whole body. On landing the hip, knee, and ankle joints should already be flexed. During multiple jumps, try not to move too far from the original take-off area. 
Knee tuck jump
Assume a relaxed upright stance, feet shoulder apart. Place the hand in front of the chest, with palms facing down. Drive the knees toward the chest and try to touch the palms of the hands, while tucking the feet under the body. 
Assume a semi-squat-position. Squat downwards, shifting your weight to the outside leg, for an immediate push-off. The inner knee and shoulder will dip, as the athlete push off his outside leg. Jump inward/across, driving the inner leg across and extending his arms and body. The inner foot will land first with the push off foot following, to balance the landing. 
Assume a relaxed upright stance. Lead into the skipping by jogging first. Perform power skipping by using a short skipping step and then with the opposite leg, thrusting the knees and toe up. Try and get as much height and power as possible, after each short step. Drive the knee up hard and fast and concentrate on lift and hang time in the air, as much as possible, while minimizing the ground contact time. 
| Conclusion|| |
Plyometric training can be a very useful tool in developing the power of your soccer player. It trains soccer players and helps prevents future injuries to their knees. Plyometric should be used with caution in this type of training. Thus we should give them a quality training than quantity training.
| Acknowledgments|| |
We express our sincere thanks to Dr. Zoheb A Siddiqui and Dr. Nayeem U Zia for helping in the review process.
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