In this issue’s ‘exercise of the month’, it’s time to take the plunge – quite literally. As PP regular John Shepherd explains, the depth jump is a plyometric exercise that almost all athletes can benefit from.

Main muscles involved: quadriceps (thigh), hamstrings, glutes (buttocks), calf muscles.

Joint motion: ankle extension, knee extension, hip extension.

Sports applicability: running (sprinting, middle and long distances), all running and jumping based sports such as tennis, football, basketball and high jump etc.
Muscular action

The depth jump is a plyometric exercise. Plyometric exercises work on the principle that a concentric muscular contraction is much stronger if it immediately follows an eccentric contraction of the same muscle. (Eccentric muscular action occurs when a muscle lengthens under load – eg the lowering phase of a biceps curl. Concentric muscular contraction occurs when a muscle shortens under load.)

The effect of a plyometric exercise is a bit like stretching out a coiled spring to its fullest extent (the eccentric contraction), then letting it go (the concentric contraction); large amounts of energy are released in a split second as the spring recoils.
Conditioning benefits

General – The depth jump provides a great base of dynamic power for the majority of sports. This is because it closely matches the sport specific speeds of movement and muscular action. Most standard weight training lifts, even when performed as quickly as possible, take 0.5-0.7 seconds to complete, whereas during a depth jump your feet may only be in contact with the ground for between 0.2 and 0.3 seconds.

Sport specific – Although the basic depth jump is very sports specific in itself, it can be made even more so by adaptation and variation (more later).
Start position

Stand on top of a strong platform 0.5-0.8m high (the greater the height, the greater the strength component, the lower the height the greater the speed component).
Action

   1. Step slightly forward off the platform. Land toward your forefeet;
   2. React as quickly as possible to the ground and spring immediately back up into the air;
   3. Use your arms to add to your speed by drawing them back prior to stepping off the platform and swinging them vigorously upward as your feet hit the ground;
   4. Keep your back in neutral alignment, ie not arched or rounded;
   5. Focus your gaze straight ahead of you.
Training tips

    * Maintain neutral posture and a balanced elevated chest position throughout the exercise. Do not attempt to absorb the landing on impact, rather react as quickly and as fast as you can, even if this sacrifices height gained;
    * The faster a muscle is forced to perform an eccentric contraction, the greater the concentric force it can generate. To help your understanding: think of a rubber ball being thrown against a wall. What happens when the ball is thrown harder? It springs back even faster and further. This is the effect you are looking for when performing plyometric exercises, like the depth jump;
    * Always warm up thoroughly before performing depth jumps;
    * Don’t perform more than two workouts a week and allow at least five days before important competitions;
    * Monitor the number of jumps performed. Depth jump volume is measured in ground contacts; avoid more than 60 in a session. Start with 3 x 6 repetitions;
    * To allow your power-producing fast-twitch muscle fibres to be at their most effective, take 30 seconds recovery between exercises and two minutes between sets;
    * Perform depth jumps on a non-slip flat surface – a sprung gymnasium floor or an all-weather athletics track are ideal surfaces;
    * You need to be in ‘the right frame of mind’ to get the most out of depth jumping. Going through the motions will not turn on sufficient neuromuscular input to optimise their performance.

Sport specific exercise progression

Single-leg depth jump (hop) for distance

This variation will up your leg muscles’ power and is a great exercise for field and racket sports players, sprinters and jumpers (where all movements are performed with an independent leg action). Note the single-leg depth jump places greater potential strain on the legs and back, as such this exercise should only be performed by those with a high degree of prior plyometric training experience.

Assume the same starting position as for the first exercise, but this time drive forward to land about 1m in front of the platform, on the same leg. React as quickly as possible to the ground and hop forward as far as you can. Maintain an upright posture and cycle your hopping leg under your body whilst in the air. Coordinate your arms with your legs, ie in a running, ‘opposite arm to leg’ style. Try 3 x 5 repetitions, alternating left and right leg sets.

John Shepherd MA is a specialist health, sport and fitness writer and a former international long jumper

Illustrations by Viv Mullett

[ 本帖最后由 bing2008 于 2008-4-13 04:20 PM 编辑 ]

- Shock Yourself into high gear

When you hear the phrase "Russian training secrets" what do you think of? Back in the early 1970's you probably would have waited in anticipation to hear the training secrets that allowed the soviet union to so thoroughly dominate competition in the olympics. Fortunately, now it's 30 years later and the old Russian training secrets have long since been revealed, - but even today that phrase will still set many people on the edge of their seats.

The Russian secret I'd like to talk about and the same one that in large part made the soviets such a dominant force on the world competition scene back in the 70's is called the shock method of training. The shock method consists of 2 very simple exercises that really don't even require any equipment, depth jumps and drop jumps.

Both of these exercises are now commonly lumped into the plyometric family of exercises and were developed by Soviet scientist and coach Yuri Verkhoshansky. The original meaning of the word plyometric (originally spelled pliometric) was intended to mean eccentric contraction.

These exercises rely on forceful eccentric contractions and were used by Soviet coaches as a "shock" method to take speed-strength ability to a new level. The neuromuscular effect is similar to hooking your muscles up to a power plant and injecting them with a very brief high current. In fact, these exercises were credited as being the secret weapon in the training of the great Soviet sprinter Valery Borzov who dominated the 100 meter dash.

Plyometrics became popular in America in the 70s. Soviet sprinters were displaying very impressive sprint times so U.S. coaches decided to go to the Soviet Union to figure out what the Russians were doing. The Americans saw the Soviet athletes stepping off of high boxes, hitting the ground, and jumping back up in the air. Upon their return to the United States, they spread the word of the magic training method and the term "Plyometrics" was coined. Soon all types of leaping and bounding drills were thrown into the same category as the original shock plyometric exericises and before long every coach in the world was using some type of supposed plyometric activity. Unfortunately, they never took into consideration the planning and conditioning that existed in addition to this type of magic training. In the Soviet Union the shock method was used in a cyclic nature which involved varying intensity levels and conditioning methods. Even today many coaches prescribe plyometric exercises without much of a thought of how they should be included in a plan.
How They Work

Recall that Force = Mass x Acceleration.

In normal training, the Mass is increased which leads to static strength development and muscular growth.

With the use of shock plyometrics, the Acceleration is increased which leads to target involuntary neuromuscular and central nervous system processes.

The ultimate goal in shock method training is to maximize the benefits of the stretch shortening cycle or plyometric reflex. You need sufficient strength in the musculoskeletal system before adhering to this type of training. A great deal of force is produced in the joints when performing any type of jumping or falling and one should concentrate on quality training.

Since shock methods increase plyometric capacity and the ability to use the stretch-shortening cycle they are beneficial for virtually any lower body explosive power movement including sprinting, jumping, agility, gymnastics etc. An experiment revealed that a group of track and field jumpers executing primarily depth jumps (all of them did 475 jumps) over a 12 week period showed greater improvement in reactive ability then a group which trained with traditional methods and executed 1472 general pushoffs (squats, squat jumps and hops with 90-95%, 70-80%, and 30-40% of 1rm and a total volume of 93 tons.
Execution

To perform a depth jump you stand on a box, step off, hit the ground, and immediately jump up as high as possible at ground contact. You should gain energy from the impact that you absorb, stabilize, and transfer to your muscles and tendons for a more explosive jump.

A drop jump is just the landing portion of a depth jump. You simply step from a box and "stick" the landing.
Differences

Although the 2 exercises both increase plyometric power and are very similar they do have a few differences. Nearly all sports movements rely to some extent on plyometric ability. Before you can put energy out you have to take energy in. After you take energy in from one direction you then have to put it out in the opposite direction. The drop jump trains more of the "taking energy in" aspect and the depth jump trains more of the "putting energy out" aspect. Because of this, drop jumps are more of a strength/force movement and depth jumps are more of a rate of force development and speed movement.

Many athletes will train only the takeoff part of a jump, with no concern for building up the capacities needed for a controlled and balanced landing. Athletes should be able to "stick" a landing, absorb the shock, and efficiently transfer that shock into a positive movement immediately.

Testing has revealed that for a shock absorbing landing with a knee bend, athletes use a resistance force 3 to 4 times their body weight. Landing performed with stiff leg joints requires a force of six to 8 times bodyweight. An athlete weighing 132 pounds requires 400 to 500 pounds of force to absorb the shock of landing. The same athlete requires 700 to 1000 lbs to land with the leg joint stiff. When an athlete lands on one leg, as in figure skating, the force at the instant of landing is 3 to 4 times bodyweight for a shock absorbing landing and five to 7 tmes when landing with stiff legs. Dealing with forces like these requires a substantial level of eccentric strength.

Both shock jumps and depth jumps will build up your reactive power which is the ability to generate the force of muscular activity immediately following a landing or the absorption of force. Drop jumps and regular strength training work well to build up plyometric capacity on the max force side of things and build landing strength or the ability to absorb and stabilize force. This trains eccentric strength or the "taking energy in" aspect. Depth jumps work to increase what happens after the force is put into the system, or the "putting energy out" side of things.
Force In vs Force Out

Watch the difference in contact times and the speed at which people change direction from "down" to "up" or from negative contraction to positive contraction when they run, jump, or cut. Depth jumps will shorten ground contact times during the amortization phase (the switch) and improve the rate of force development and velocity that occurs after the transition. Drop jumps will heighten the amount of force we can take in at the transition which will give us more potential to put force out.

So, for someone who's limiting factor is force absorption or strength, drop jumps are a huge benefit. This type of athlete won't be able to change direction quickly because they won't be able to stabilize the negative force to begin with. Think of someone who is the direct opposite of Barry Sanders. For someone who needs speed out of the transition, depth jumps are a better choice. In fact, when it comes to pure speed, a study revealed that the max speed in a sprint correlates best to how much force one can put out in the first .100 (1 tenth of a second) of a depth jump.



If your best vertical jump from a regular standing position is better then your best depth jump from even a very low box height (~ 8 inches) then you should use landings via drop jumps to increase your ability to gather energy and optimize force absorption capabilities. If your depth jumps are higher then your regular standing vertical jump then you are a good candidate for depth jumps. However, nothing is cut and dry here. There is considerable overlap with these training methods so sometimes the drop jump will be used if a person is slow during transition due to inefficiency at absorbing energy.
Strength Recommendations

It has been stated that an athlete should be able to squat 1.5 x times their bodyweight before performing shock plyometrics in order to avoid injury and optimize progress. One thing that must be made clear is that these training methods originally called for box heights of 1 meter or more. When absorbing the force from this type of landing it is necessary to have a high level of strength. Realize you probably won't get much benefit from any plyometric exercises until you have a base level of strength. However, even little kids jump off of playground equipment and furniture all day long without injury. My recommendation is that you should not perform depth jumps from a box height of greater then 18 inches until you can squat 1.5 x or more your bodyweight. However, it is perfectly fine to perform drop jumps from a height equivalent to your best vertical jump regardless of your strength levels. In fact drop jumps combined with general strength training are a great tool to not only increase your eccentric strength and ability to deal with high forces, but also teach basic movement mechanics with force.
Box Height Recommendations

All sorts of box height recommendations are thrown out for depth jumps and the original recommendations called for box heights of .75-1.15 meters. A very simple and effective box height recommendation is to perform your depth jumps from the height of a box that allows you to jump the highest immediately after ground contact. As stated earlier, if you can't perform a depth jump from a box of any height and get up higher then you can in a regular standing jump then you shouldn't be using depth jumps to begin with. One should aim to increase the speed, acceleration, and height of the jump before increasing the drop height. According to the founder of shock method training,Verkhoshansky, you should not spend in excess of 0.2 of a second on the ground after landing.

Drop jumps should be done from a box height that enables you to absorb the most energy without faltering. Aim to "stick" the landing soft and silent on the balls of your feet just like a gymnast doing a dismount. If the heels hit the ground the box is too high and if there is a thud at impact the box is too high. When the box is the correct height the jump should be silent and soft with a reflexive gathering of energy and often a reflexive bounce at impact. When your body is gathering energy efficiently you will feel your system want to reflexively use that energy to advance out of the landing. Generally a good starting point for drop jumps is from a box 20% higher then the best vertical jump and eventually on up to 1.15-1.25 meters.
Performance Recommendations

Both variations of shock training should be performed on a surface that has some give to it to avoid injury. Grass works well as does the use of solid rubber mats. You should land as far away from the box as the box is high. So, if you're standing on a 30-inch box you should land approximately 30 inches away.

When executing depth jumps you should use a simple athletic stance position just as you would whenever you jump.

Drop jump performance can vary. You can land in a regular athletic stance for general carryover, in a stiff-legged stance to emphasize lower leg force production ability, in a 1/2 squat to emphasize the hips and hamstrings, in a split squat stance to emphasize all around balance, and in a 1-legged stance to heighten the magnitude of force absorbed.
Volume Recommendations

The optimal dosage of depth jumps or drop jumps should not exceed 40 combined ground contacts per session for well conditioned athletes and 20 ground contacts per session for lesser conditioned athletes. As a guideline, the dosage of shock plyometrics should not exceed 5-8 repetitions in 1 set and sets of 3-5 work well with up to 30 seconds between reps and up to 10 minutes between sets. Remember that these are a speed-strength tool not an endurance tool. Maximum muscular recruitment requires that you stay fresh. High volumes of consecutive repetitions are not possible or advisable.

Using the above volume shock jumps should be performed once or twice per week in training sessions devoted to specialized speed-strength or strength training.

For best results use the above recommended volumes of shock jumps in short 3-4 week blocks preceeded by a block of higher volume strength training. Another option for someone who already has a great deal of strength is to perform a block of drop jumps in conjunction with strength training, followed by a block of depth jumps and power training, followed by another block of shock jumps with general explosive exercises. The set-up would be performed twice per week and look like this:

Week 1-3 Low level drop jumps/Strength (squat)

Week 4-6 Depth Jumps/Power training (speed squat)

Week 5-7 Drop jumps/General explosive bodyweight exercises



Depth jumping variations give quick results but the gains are just as quick to plateau. Low level variations of drop jumps can be used throughout the year but it's best to really focus on shock training 2-3 times through the year when you need to bring your level of speed-strength to a peak.

-Kelly

请看
http://www.youtube.com/watch?v=hb4JwBNY56s

超等长练习机制与跳深训练法研究述评
A Review on the Studies of Ploymetric Exercise Principle and Jump Drop Training
<<天津体育学院学报 >>2005年02期
罗炯 , LUO Jiong

通过对国内外有关超等长(Ploymetric)收缩机制的研究回顾,提出了训练对象的力量基础、训练水平、体重、训练负荷等差异决定了超等长训练方式的特殊性.跳深作为发展运动员下肢爆发力的一种超等长练习的代表,其高度选择、动作的变化、负荷强度等可变因素必须与具体运动专项相结合,遵循区别对待原理, 才能有效地发展运动员的专项力量素质.

跳深练习对增加运动员腿部爆发力作用的研究
The Research about the Effect of Depth Jumping Exercise for Increasing Athlete's Legs Power
<<体育与科学 >>2002年05期
郑彩壮

跳深练习是力量练习中的一种肌肉的超等长练习,很多教练员认为这种练习能够有效地提高运动员腿部爆发力和弹跳能力,因此将其作为在训练中经常采用的手段.但是也有很多研究表明,这种练习的效果并不优于其它一些发展腿部力量的练习,而且跳深练习还容易造成运动员的肌肉损伤,建议教练员在选择这种练习时要慎重, 特别是面对训练水平较低的青少年运动员.

跳深练习对提高爆发力训练效果的实验研究
Experimental Research on the Training Effect of Practicing Longitudinal Springing on the Improvement of Explosive Force
<<沈阳体育学院学报 >>2004年05期
贾桂云 , 张芝贤

通过采用有反向引导动作和无反向引导动作伸展跳跃的练习以及新式跳深练习方法的试验,结果表明运动员弹跳能力都提高了20％～30％.相反采用传统训练方法的对照组成员的弹跳力却没有明显的变化,认为新式跳深练习能使弹跳力提高.

不同高度间距组合跳深练习与起跳效果的非线性关系分析
The Nonlinear Analysis Between Drop-Jump of Different Depth and Distance Combination and the Effect of Jump
<<天津体育学院学报 >>2006年06期
部义峰 , 李世明 , 韩静 , 熊安竹

跳深练习是一种发展肌肉爆发力的有效形式,在理论和实践上的应用不断深入,特别是对跳深高度的研究颇多,而对跳深间距的研究却很少,不同高度、间距组合跳深练习的研究国内未见报道.因此,在通过实验条件下获得不同高度、间距组合跳深练习对踏跳效果的影响程度,以及不同组合跳深练习与踏跳效果间的非线性关系, 进一步丰富跳深练习的方法,更为深入了解二者关系,为跳深练习更加广泛的应用提供方法、理论上的依据.

不同高度间距组合跳深练习与起跳效果的非线性关系分析
The Nonlinear Analysis Between Drop-Jump of Different Depth and Distance Combination and the Effect of Jump
<<天津体育学院学报 >>2006年06期
部义峰 , 李世明 , 韩静 , 熊安竹

跳深练习是一种发展肌肉爆发力的有效形式,在理论和实践上的应用不断深入,特别是对跳深高度的研究颇多,而对跳深间距的研究却很少,不同高度、间距组合跳深练习的研究国内未见报道.因此,在通过实验条件下获得不同高度、间距组合跳深练习对踏跳效果的影响程度,以及不同组合跳深练习与踏跳效果间的非线性关系, 进一步丰富跳深练习的方法,更为深入了解二者关系,为跳深练习更加广泛的应用提供方法、理论上的依据.

跳深跳远与三级跳远跨步跳起跳的动力学比较研究
Kinetic Comparative Study on Taking-off of Depth-long-jump and Long Jump
<<北京体育大学学报 >>2005年07期
王薇薇 , WANG Wei-wei

采用文献研究及在实验条件下的动力学测试,对两步助跑跳深跳远练习与三级跳远跨步跳起跳力量在形式及内容上的相似程度和差异点进行对比分析.结果显示,两步助跑跳深跳远练习可以作为发展三级跳远跨步跳起跳力量的专门训练手段.

跳深纵跳练习对跳高运动员起跳腿"承受能力"的测定与分析
Measurement and Analysis on Enduring Ability of Jump Leg as Adopting Deep-jump and Vertical-jump by High Jumpers
<<沈阳体育学院学报 >>2006年01期
刘建 , 李世远 , LIU Jian , LI Shi-yuan

采用运动学和动力学相结合的生物力学研究方法对跳高运动员下肢肌的承受能力进行研究,得出如下主要结论:①跳深纵跳练习可以作为提高跳高运动员起跳能力的专项练习;②跳高运动员起跳腿的承受能力直接影响缓冲和蹬伸过程,并最终影响起跳效果;③膝关节和踝关节,尤其是踝关节是二级跳高运动员下肢承受能力的薄弱环节.同时膝关节是最大缓冲时刻的"关键性环节";④二级跳高运动员产生最大反跳高度的适宜高度为(35.0±4.56)cm,最大反跳高度为 (48.00±3.78)cm;⑤适宜高度跳深的冲击载荷与摸高成绩、适宜高度跳深纵跳的反跳高度与助跑摸高成绩均呈高度相关,两者均是评价运动员起跳能力的重要指标.