Plyometrics

[BSHC]

Plyometrics

From Wikipedia, the free encyclopedia

 

Plyometrics is a type of exercise training designed to produce fast, powerful movements, and improve the functions of the nervous system, generally for the purposes of improving performance in a specific sport.

Plyometric movements use the strength, elasticity and innervation of muscle and surrounding tissues to jump higher, run faster, throw farther or hit harder, depending on the desired training goal.

 Procedure

Plyometric training involves practicing plyometric movements to toughen tissues and train nerve cells to stimulate a specific pattern of muscle contraction so the muscle generates as strong a contraction as possible in the shortest amount of time.

A plyometric contraction involves first a rapid eccentric movement, followed by a short amortization phase, then an explosive concentric movement, which enables the synergistic muscles to engage in the myotatic-stretch reflex during the stretch-shortening cycle.

Plyometric exercises use explosive movements to develop muscular power, the ability to generate a large amount of force quickly. Plyometric training acts on both the musculotendinous and neurological levels to increase an athlete's power output without necessarily increasing their maximum strength output. Plyometrics are used to increase the speed or force of muscular contractions, often with goals of increasing the height of a jump or speed of a punch or throw.

 Physics of plyometrics

Muscular power is determined by how long it takes for strength to be converted into speed. The ability to convert strength to speed in a very short time allows for athletic movements beyond what raw strength will allow.

Thus an athlete who has strong legs and can perform the freeweight squat with extremely heavy weights over a long duration may get less distance on a standing long jump or height on a vertical leap than a weaker athlete who is able to generate a smaller amount of force in a shorter amount of time. Though the plyometrically trained athlete has a lower maximal force output and may not squat as much, training allows them to compress the time required to reach their maximum force output, allowing them to develop more power with each contraction.

 Musculotendinous component

For a muscle to cause movement, it must shorten; this is known as a concentric contraction. There is a maximum amount of force with which a certain muscle can concentrically contract. However, if the muscle is lengthened (eccentric contraction) just prior to the contraction, it will produce greater force through the storage of elastic energy. This effect requires that the transition time between eccentric contraction and concentric contraction (amortisation phase) be very short. This energy dissipates rapidly, so the following concentric contraction must follow the eccentric stretch before this occurs. The process is frequently referred to as the "stretch shortening cycle", and is one of the underlying mechanisms of plyometric training.

 Neurological component

In addition to the elastic-recoil of the musculotendonous system there is a neurological component. The stretch shortening cycle affects the sensory response of the muscle spindles and golgi tendon organs (GTO). It is believed that during plyometric exercise, the excitatory threshold of the GTO's is increased, meaning they become less likely to send signals to limit force production when the muscle has increased tension. This facilitates greater contraction force than normal strength or power exercise, and thus greater training ability.

The muscle spindles are involved in the stretch reflex and are triggered by rapid lengthening of the muscle as well as absolute length. At the end of the rapid eccentric contraction, the muscle has reached a great length at a high velocity. This may cause the muscle spindle to enact a powerful stretch reflex, further enhancing the power of the following concentric contraction. The muscle spindle's sensitivity to velocity is another reason why the amortisation phase must be brief for a plyometric effect.

A longer term neurological component involves training the muscles to contract more quickly and powerfully by altering the timing and firing rates of the motor units. During a normal contraction, motor units peak in a de-synchronized fashion until tetanus is reached. Plyometric training conditions the neurons to contract with a single powerful surge rather than several disorganized contractions. The result is a stronger, faster contraction allowing a heavy load (such as the body) to be moved quickly and forcefully.

Therefore, a plyometric exercise involves:

1. An eccentric contraction
2. A brief amortisation phase (no change in muscle length)
3. A short concentric contraction delivering maximum force in a short period of time

 Safety considerations

Plyometric exercises carry increased risk of injury due to the powerful forces generated during training and performance, and should only be performed by well-conditioned individuals who are under supervision. Good levels of physical strength, flexibility and proprioception should be achieved before commencement of plyometric training.

The specified minimum strength requirement varies depending on where the information is sourced and the intensity of the plyometrics to be performed. Chu (1998) recommends a participant should able to perform 5 repetitions of the squat exercise at 60% of their bodyweight before doing plyometrics. Core body (trunk) strength is also important.

Flexibility is required both for injury prevention and to enhance the effect of the stretch shortening cycle.

Proprioception is an important component of balance, coordination and agility, which are also required for safe performance of plyometric exercises.

Further safety considerations include:

• Age - low-intensity and low-volume only for athletes under the age of 13 or for athletes who squat less than 1.5 times their bodyweight.

• Surface - some degree of softness is needed. Gymnastics mats are ideal, grass is suitable. Hard surfaces such as concrete should never be used.

• Footwear - must have adequate cushioning and be well fitting.

• Bodyweight - athletes who are over 240 pounds (109 kg) should be very careful and low-intensity plyometric exercises should be selected.

• Technique - most importantly, a participant must be instructed on proper technique before commencing any plyometric exercise. They should be well rested and free of injury in any of the limbs to be exercised.

Plyometrics is not dangerous, but the potential for high intensity and stress on joints and musculo-tendonous units makes safety a strong prerequisite to this particular method of exercise. Low-intensity variations of plyometrics are frequently performed in various stages of injury rehabilitation, indicating that correct performance is valuable and safe for increasing muscular power in all populations.

 Additional Information

Most exercises involve a muscular contraction that starts off rapidly, but decelerates suddenly before the end of the repetition. For example, lifting a barbell involves jerking the weight quickly into the air, then bringing this motion to a sudden halt. Plyometric exercises are characterized by the lack of such a decelerative phase. They are open-ended movements into free space. Other animals take advantage of this effect; one is the kangaroo. If a kangaroo needed to use 100% new energy to contract its leg muscles every time it jumped, it would not be able to jump very far consistently. However, because of the muscles' ability to store energy from its previous jump before like a spring, the kangaroo only needs to use a fraction of the total energy in the jump.

Physical educators have long used various plyometric apparatus—including medicine balls, and Indian clubs. One plyometric exercise involves catching and tossing a medicine ball to an assistant while the exerciser lies on his back. The triceps and chest muscles work both while they are lengthening (catch phase) and while contracting (toss phase). The clap press up is another example of a plyometric exercise.

isometrics

concentric

eccentric

plyometrics

Definition of plyometrics ( dictionary)

Exercise without weights or machines: a free body movement exercise system using no weights or machines, but emphasizing calisthenics and repeated movements such as jumping high off the ground ( takes a singular verb )

Exercise involving repeated rapid stretching and contracting of muscles (as by jumping and rebounding) to increase muscle power.

A type of exercise using explosive movements to develop muscular power, esp. bounding, hopping, and jumping.

A type of fast exercise in which the muscles are not allowed to fully contract after being extended, typically involving jumping and bouncing.

Any exercise in which muscles are repeatedly and rapidly stretched ("loaded") and then contracted (as in jumping high off the ground or in push-ups with a clap between them). The aim of plyometrics is to improve muscle power.

플라이오 메트릭스의 정의

구소련의 운동선수들을 위해 개발되었던 플라이오메트릭스는 1975년 육상계의 전설적인 지도자 프레드 윌트를 통해 소개되었습니다.

웨이트 트레이닝이 근육을 더 우람하게 만드는 반면,

플라이오메트릭스는 근육의 신전 반사를 향상시켜서 또는 에너지를 운동으로 전환시키는 스피드를 향상시켜서 근육반응을

더 빠르게 만들어 줍니다.

* 플라이오 메트릭스의 종류

1. 목표 : 더 빨리 뛰기

플라이오 : 박스 점프

쪼그려 앉았다가 벤치로 점프해 올라간다. 항상 앞꿈치 부분으로 착지하도록 한다. 가급적 빨리 벤치에서 뛰어내려 지면을 밟는다.

두 동작을 합쳐서 10회 실시한다.

2. 목표 : 더 높이 점프하기

플라이오 : 뎁스(Depth) 점프

오른발을 벤치에서 내딛는다. 착지하자마자 그 즉시 온힘을 다해 수직방향으로 점프하라. 다리를 바꿔가면서 반복한다.

3. 목표:더 빨리 움직이기

플라이오 : 스피드 스케이터(Speed Skater)

막대 두 개를 1.2m 간격으로 설치한다. 오른발을 앞으로 내밀고 왼발을 뒤에 두는 것으로 시작한다.

왼쪽으로 몸을 날리면서 왼발로 착지한다. 착지하는 충격을 줄이기 위해 왼쪽 무릎을 굽힌다.

그 즉시 점프해서는 스피드 스케이터가 하는 것처럼 오른발로 착지하도록 한다. 두 동작을 합쳐서 10회 실시한다.

4. 목표 : 강하게 때리기

플라이오 : 메디신볼 슬램(Medicine-ball Slam)

양쪽 무릎을 약간 굽히고 메디신볼을 가슴 높이로 잡는다. 볼을 올려서 머리 뒤로 가져간다.

그런 후에 온 힘을 다해 볼을 땅바닥에 내려 꽂는다. 공이 튀어 오르면 공을 붙잡는다. 두 동작을 합쳐서 5회 실시한다.

5. 더블-레그 바운딩 (Double-Leg Bounding)
다리를 어깨 너비로 벌리고 선 채로 양발로 두 계단씩(총계단수 22~25개)뛰어 오른다.

처음부터 두 계단씩 하는 것이 힘들면 한 계단씩 한다. 계단을 다 오르면 1세트가 끝난다. 1세트가 끝나면 다시 내려가서 반복 훈련한다.

6. 점프 & 스프린트 (Jump & Sprint)
3~4 보 폭의 거리로 계단이 시작되는 지점까지 뛰어가서 두발로 첫 계단을 뛰어오 른다. (균형을 잘 잡고 안전하게 착지한다.)

그런 다음 나머지 계단을 두 개씩 뛰어서 올라간다. 그렇게 22-25 회 실시하면 1세트가 끝난다. 걸어 내려가서 다시 반복 훈련한다.

7. 더블-레그 지그재그 (Double-Leg Zigzag)

더블-레그 바운딩과 같은 방법으로 하되, 똑바로 뛰지 않고 지그재그로 점프한 다. 한번에 한 계단씩 오르고 두 발은 모은다.

8. 스테어 스프린트 (Stair Sprint)
두 계단 씩 22~25회를 큰 보폭으로 뛰어 올라간다. 1세트가 끝나면 걸어 내려가서 반복한다.

조금 쉽게 이야기 하자면

플라이오메트릭 운동이란

① 근육을 급격히 (컨센트릭)수축한 후

② 즉각적으로 (익센트릭)신장 해주는 운동을 뜻합니다.

한마디로 근육을 확 접은 다음, 확하고 다시 펴주는 동작을 반복하는 운동을 뜻합니다.

이러한 훈련은 최단시간에 급격한 움직임을 지구력 있게 컨트롤된 자세에서 만들어 주기 때문이며,

결국 운동시 순발력 향상으로 나타납니다.(순간적인 파워를 낼 수 있는 역도, 농구 등에 적합한 운동법이죠)

Background

Plyometric exercises are specialized and very intense training techniques, which are used to develop muscular power, referring to the relationship between strength and speed. Plyometrics include any exercise where the muscle is contracted eccentrically (stretched) then immediately moved concentrically (contracted). The ability to generate a force in a short time allows for athletic movements beyond what strength alone will allow. For a muscle to cause movement, it contracts concentrically. Various muscles have different maximum amounts of power with which they can contract. However, if the muscle is lengthened (eccentric contraction) just prior to the contraction, it will actually produce more power. In order to produce this effect, the time between the eccentric contraction and the concentric contraction must be very short.

An example of a plyometric exercise is push-ups with a clap in between each push-up. In this case, the pectoral muscles are elongated and loaded by the downward force of your body, stretching eccentrically, then immediately contracted to push the body back up, stretching concentrically. The clap push-up, as opposed to a normal push-up, ensures that there is only a short amount of time between the eccentric and concentric contractions of the muscle. Examples of lower body plyometrics include depth jumps, multiple jumps, marches and lateral jumps, often involving boxes or platforms, and weight vests. Mid-section plyometrics include the broomstick twist, and twists, side-throws and sit-ups using a medicine ball. Upper body plyometrics involve medicine ball exercises and different types of push-ups.

The word "plyometrics" has been around since the 1960s but athletes were using the technique many years before the term was coined. Some of the exercises commonly used today include jumping off a box and rebounding off the floor onto another, higher box while either carrying weights, or more often wearing a weight vest.

While plyometrics have been shown to increase power, experts' opinions vary regarding the safety of these exercises. Many well-respected fitness experts argue the benefits and effectiveness of plyometric exercise. However, there are others who strongly deny these benefits and argue that plyometric exercises are extremely unsafe and the risk of injury far outweighs any potential benefits. Most experts state that a thorough grounding in weight-training is essential before starting plyometrics.

Technique

A thorough warm up is recommended prior to plyometric training. This typically includes jogging, stretching, striding and general mobility especially about the joints involved in the planned plyometric session. A cool down usually follows each session.

For bounding exercises, surfaces such as grass or resilient surfaces are used. Cement floors are usually avoided due to lack of cushioning. Individuals use well-cushioned shoes that are stable and can absorb some of the inevitable impact. All athletes should undergo general orthopedic screening before engaging in plyometric training.

Physical educators have long used various plyometric apparatus-including medicine balls, jump ropes, and Indian clubs. One plyometric exercise involves catching and tossing a medicine ball to an assistant while the exerciser lies on his back. The triceps and chest muscles work both while they are lengthening (catch phase) and while contracting (toss phase).

The following are examples of plyometric exercises:

Bounding and hurdling: This is a form of plyometric training, where over sized strides are used in the running action and extra time spent in the air. Two-legged bounds reduce the impact to be endured, but to increase the intensity one legged bounding, or hopping, can be used. Bounding upstairs is a useful way to work on both the vertical and horizontal aspects of the running action. Multiple jumps over a series of obstacles like hurdles may be valuable drills for athletes training for sprinting or jumping events.

Drop jumping: This exercise involves the athlete dropping (not jumping) to the ground from a raised platform or box, and then immediately jumping back onto the platform. The drop down gives the pre-stretch to the leg muscles and the vigorous drive upwards the secondary concentric contraction. The exercise will be more effective the shorter the time the feet are in contact with the ground. The height of the drop is usually in the region of 30 to 80 cm. Drop jumping is a relatively high impact form of plyometric training and would normally be introduced after the athlete had become accustomed to lower impact alternatives, such as two-footed jumping on the spot.

Medicine ball: This involves a person lying on the ground face up. A partner then drops a medicine ball down towards the chest of the athlete, who catches the ball (pre-stretch) and immediately throws it back.

Press ups & hand clap: Press-ups with a hand clap in between is a particularly vigorous way to condition the arms and chest. The pre-stretch takes place as the hands arrive back on the ground and the chest sinks, and this is followed quickly by the explosive upwards action. The time in contact with the ground should be kept to a minimum.

Theory/Evidence

The underlying principle of plyometric training is the stretch-shortening cycle. As a muscle stretches and contracts eccentrically, it lengthens while it contracts and produces storable elastic energy. If the muscle then contracts concentrically, shortening while it contracts, this stored elastic energy can be used to increase the force of the contraction. Therefore, a muscle stretched before it contracts will contract much more forcefully. Plyometric training places increased stretch loads on the working muscles. As the muscles become more tolerant to the increased loads the stretch-shortening cycle becomes more efficient, meaning the muscle stores more elastic energy. It can transfer from the eccentric or stretching phase to the concentric or lengthening phase more rapidly, thus generating peak power. These types of exercises can be used in many different sports training, for example, to improve a boxer's punch, or increase a basketball player's vertical jump.

While many well respected fitness experts argue the benefits and effectiveness of plyometric exercise, others strongly deny these benefits and dispute that plyometric exercises are exceedingly unsafe and the risk of injury far outweighs any potential benefits.

Based on one study, plyometric exercises may increase peak bone mass in adolescent girls as compared to girls who are not undergoing plyometric training after a period of nine months. The plyometric exercises used in this study include squats, lunges and calf raises using weighted vests, and hopping, bounding and box depth jumps. More high-quality studies are needed to draw any firm conclusions.

Safety

Plyometrics has received much blame for overtraining and is thought to cause an increased risk of injury. Plyometrics, like other forms of fitness training, carries risks when used incorrectly and recklessly. The safety of plyometric exercises may depend on the frequency, length, and intensity of the exercises preformed. Consult with a qualified healthcare professional before making decisions about new exercise routines.

Most experts believe that a solid strength base is required before starting a plyometrics program, meaning an individual should have the ability to squat at least twice their bodyweight or leg press at least 2.5 times their bodyweight. These basic requirements may help avoid injuries when starting a plyometrics program.

It is not recommended that anyone under the age of 16 use plyometrics, particularly the more intense plyometric exercises, unless a fully qualified coach or physical trainer recommends otherwise. Because of the relatively immature bone structure in preadolescent and adolescent children the very great forces exerted during intensive depth jumps should be avoided.

Particular injuries that may be associated with the high impact involved in plyometric training include but are not limited to back pain and injury, spinal shrinkage, heel-pad bruising, and patellar tendonitis (jumper's knee).

Plyometric exercises should be performed on a soft surface such as grass or a synthetic running track.

Two sessions of plyometrics per week is viewed as more than enough. A maximum of three sessions of plyometric exercises in a week should not be exceeded. It is important not to perform too many repetitions in any one session. The amount of repetitions performed should be based on a person's physical conditions and abilities.

As with other exercises warming up is a crucial deterrent of injuries. It is recommended to spend 10 minutes of jogging or skipping followed by 5 to 10 minutes of stretching the muscles involved before the beginning of each plyometrics program. It is also important to remember to stretch the lower back.

Read more: http://www.righthealth.com/topic/Eccentric_Exercise/overview/NaturalStandard20_s#ixzz1SCAnLPiv