SINGLE POSTCelebrating our 10th Anniversary!

March 21, 2013

By: Michael Everts
 

Enhancing Strength and Performance Training with Plyometrics

In more than ten years of personal training, I have come across many clients with the same “I’ve always done it this way and have seen great results?syndrome. More often than not, this client is explaining that the workouts they performed in college and during their twenties are the correct exercise prescription, but due to plateaus, injury, work, and or lifestyle have not been able to focus and apply themselves as they once did.

Most of these people have in common the same type of general strength training ?slowly lifting heavy weights with moderate rest periods between each set. Because of the high efficiency at which our body breaks down and repairs muscle, peak metabolism, and advantageous hormonal ratios, In our late teens to mid twenties, this style of training produces pleasing strength and cosmetic results. With such gratifying results, people will spend years repeating these routines, developing predictable patterns leading to developmental plateaus, confusion, frustration and injury. The most significant factors, in terms of variety, lacking in these routines are speed, coordination, agility, and power.

There are many appropriate methods and techniques to incorporate such variety. Plyometric training is one such valuable tool in the personal trainer’s arsenal.

Plyometrics is a style of training incorporating quick and explosive movements, designed to improve speed, power, and neuromuscular and motor function (agility and coordination). Plyometric training is generally most often found in athletic training programs for the purpose of improving performance in sports.

For the athlete, plyometric movements, where the muscle is loaded and then contracted rapidly, recruit elasticity and strength of muscles and tissues in order to move or change direction quicker, throw harder or further, or jump higher depending on the sport. Plyometric training can improve the speed or force of muscular contractions, usually with these athletic goals in mind. Plyometrics, however, need not be limited to just the athlete. A common nuisance for the fitness novice is the inability to recognize or feel the involvement or recruitment of the targeted primary muscle during a particular exercise. Unless there is a significant attention or focus deficit, this is likely a result of a poorly functioning neuromuscular system, or a deficiency in the link between the mind and the muscles.

This type of deficiency can result in lack of motivation, improper form when exercising, and injury. The long term practice of proper plyometric training is proven to build efficiency in neuromuscular connections between the nervous system and muscle.

Plyometrics, used correctly can be a very useful part of a comprehensive personal training plan. Whether the goal is improved strength and speed for functional or athletic use or to improve coordination and efficiency in your workouts or daily activity, incorporating plyometric training is a great enhancement to a stale workout program.
Priciples of Plyometrics ?The Stretch-Shortening Cycle

Plyometric training works by teaching the muscles to work to near maximum capability. The total amount of force that a muscle can create is achieved during the lengthening of a particular muscle (eccentric contraction).

When a muscle is shortened (concentric contraction) immediately following the eccentric contraction, energy usually lost during the set, can be utilized. This process where a muscle lengthens while it contracts, producing elastic energy used to increase the force of the immediate following shortening, defines plyometrics. This process is called the stretch-shortening cycle.

For the purpose of full understanding, necessary definitions of contractions are as follows:

1. Concentric Contractions ?Form of muscle contraction occurring when the muscle fibers shorten as tension develops in opposing resistance.
2. Eccentric Contractions- Form of muscle contraction occurring when activated muscles are forcibly lengthened.
3. Isometric Contractions ?A contraction of a muscle without changing the length of the muscle.

An example of a concentric contraction would be the pushing straight up phase of the pushup when the extensors in the elbow contract concentrically to enable to elbow to be straightened in opposition to the weight of the body. When the weight of the body is then lowered, the muscle contracts eccentrically.

Adding plyometrics to your current training program is easy, as it requires minimal equipment and can be done almost anywhere. Plyometric exercises involve movements like hopping on one foot, jumping up and down, throwing, sprinting, and even skipping. These movements are especially effective when used variably in the forward, side, and rotational planes of movement.

In all of these movements, the same cycle is performed ?Increased stretch loads are taxed to the targeted muscles. The muscles become more capable of handling the increased loads and the muscle can store more elastic energy. The transition from the shortening phase to lengthening phase occurs faster. A muscle stretched before it contracts will contract more forcefully. The result is enhanced power.
Plyometrics Improve Strength, Speed and Neuromuscular Performance

Adding plyometric exercises to your training program can improve your speed and power, as well as help you gain more neuromuscular coordination, agility, and balance.

Consider the act of jumping from the floor on to a stack of blocks and quickly jumping back to the floor. When you jump from the floor up to the step, the muscles in your legs contract eccentrically working as a powerful breaking effect to safely slow down your momentum and stop the forward progress of your body (this is realized as a partial knee bend). This creates the potential for a powerful concentric muscle action.

When you quickly spring back to the floor your muscles contract concentrically to spring you off the step, taking full advantage of the activity in the muscles undergoing the eccentric muscle action (stretch reflex). This ability to create a more forceful and explosive muscular action, is the basic principle of plyometric training.

Because this style of training takes advantage of natural elasticity in your muscles, you can compare it to firing a slingshot. The harder you pull or stretch the elastic bands on the slingshot, the faster it fires and the more powerful the shot.

Consider again, the jumps on and off of the stacked blocks. The partial knee bend before each jump and return jump will create more force the quicker the transition between the bend and the jump. This is because the more rapidly the muscle is stretched, the more rapidly it will “snap?back. The exercise can be performed different ways, depending on different goals. For example, taking a longer jump to reach the blocks or stacking the blocks higher will result in generating more power allowing you to gain more distance or height in your jump.

A study by Western Michigan University published in the Journal of Sports Science and Medicine in 2006 studied the effects of plyometric training on agility and motor performance. The report was based on a six week program consisting of exercises similar to these block jumps, such as side to side ankle hops, double leg hops, and standing long jumps (I will post a link to the full article in the research section of this website and at ww.fit-dc.com).

Results of the training based on their testing measures indicated that the plyometric training improved because of either better motor recruitment or neural adaptations. The report speculates that “improvements were a result of enhanced motor unit recruitment patterns. Neural adaptations usually occur when athletes respond or react as a result of improved coordination between the CNS (central nervous system) signal and proprioceptive feedback.?The report continues: “However, we could not determine if neural adaptations occurred via synchronous firing of the motor neurons or better facilitation of neural impulses to the spinal cord…Therefore, more studies are needed to determine neural adaptations as a result of plyometric training and how it affects agility.?/p>

While the study is inconclusive about the precise neural adaptations and how exactly they affect agility and proprioception (awareness and sensitivity of body orientation, balance, posture, and movement), it is clear motor performance is shown to improve. Also significant in this study, is the fact that these improvements to the neuromuscular system occurred in as little as six weeks.

This study compliments many other research findings with similar conclusions.

There are also a slew of various other training studies showing that plyometrics can improve performance in sprinting speed, vertical and long jumping, long jumping, and balance and coordination. These studies also support the notion that a relatively brief trial of plyometric training is required to improve performance in these areas.

Adding only a few plyometrics (one to three exercises ?two or three sets of 8-10 repetitions) a couple times a week can improve motor performance, speed, agility, power in as little as six to ten weeks. This benefit is also applicable to upper body training. Several types of explosive pushups can enhance upper body power in throws and other movements. Plyometrics and Athletic Performance

I am just one of many trainers, coaches, and other fitness professionals that believe plyometric training is a necessary component of athletic training.

Most sports share the requirement of a significant amount of explosive power, whether in throwing, kicking, running, or jumping. These movements in soccer, football, basketball, track and field, and other sports require intense training techniques that produce extremely fit individuals. The quickness at which an athlete can convert strength to speed is more significant to athletic movement than just brute strength. For example, a basketball player who can leg press extremely heavy weights at a slow pace, may be out jumped vertically by an athlete with a weaker leg press who has the ability to generate less force but in less time.

Excellence in athletic performance in sports, in general, is not the result of maximum strength (the ability to generate force), but of power ?how rapidly the athlete can generate strength. The ability to increase leg press weight from seven hundred to eight hundred pounds is less significant than improving the speed at which the athlete can move near-maximum weight.

Plyometric training can translate for the athlete into a faster bat speed and more powerful swing for the baseball player, a more effective take-down move for the wrestler, or the ability for an offensive lineman in football to get off the line quicker.
Plyometrics in Injury Prevention and Rehabilitation

Plyometric training is most often discussed in topics of performance enhancement, and less often recognized for its significant role in injury prevention and rehabilitation.

Due to the muscles rapid transition from the fully stretched position to the concentric contraction, the muscle is conditioned at its most vulnerable point during plyometric exercises. Additionally, rehabilitation programs that focus only on concentric muscle contractions and neglect the much more force capable eccentric muscle contractions can lead to repeat injury.

In the prevention and rehabilitation stages of training, this conditioning prepares the athlete/training client for the strain of increased intensity in workout programs and in competitive sporting events. Training solely with the narrow focus of concentric muscle contraction does little to prepare for the force of future eccentric contractions.

Even with these benefits, plyometrics are intense and are not for those completely new to exercise. Plyometric training applies great force to ligaments and tendons and can be very stressful to un-conditioned muscles and joints. This training should be performed with appropriate precautions and preferably with initial consultation with a personal trainer or fitness professional that can make sure the movements are executed at the proper level with correct form.
Plyometrics Applied

To get the most benefit from plyometrics, it is best to consult a personal trainer who can initiate an overall fitness program with the eventual addition of plyometric training. A trainer or coach can properly asses you current abilities and deficiencies in strength, core stability, proprioception, and flexibility.

The fitness novice or new athlete would not begin with plyometrics, but would build up to it. The risk of injury from these exercises is greatly reduced when performed with qualified supervision present. The stretch-shortening cycle can place much force on the musculoskeletal system, especially on the tendons and ligaments, and those with serious knee or back injuries should avoid this type of training.

The great demand and variety of explosive movements in plyometrics requires a solid base of strength, endurance, proprioception, core stability, alignment, and flexibility. An initial conditioning program would develop this base, incorporating stretching, aerobic training, and resistance training as the foundation.
In addition to proper supervision, the following guidelines should be observed:

1. Avoid performing plyometrics on hard surfaces. They are best performed on grass, rubber gym flooring, dirt, or any surface with shock absorbing qualities such as artificial turf or a rubberized running track.
2. Prepubescent children should avoid repetitive and intense plyometric training.
3. It is important to warm up before a plyometric workout. The workout should include aerobic activity and dynamic stretching, with special attention paid to the hamstrings and lower back.
4. To prevent lower back strain, keep the back erect and avoid bending or leaning over during jumps.
5. Do not rush rest periods. Recovery is important, and the focus of the exercises should be speed and proper form and technique, not just to run out of breath. If your form is compromised during the exercise, it is time to rest.
6. If training for a specific sport, match exercises to typical planes of movement. For example, basketball players will benefit more from vertical plane plyometric movements, where as a runner will benefit more from exercising in forward planes of movement.

Examples of Plyometric Exercises

By making use of the stretch reflex in your muscles, movements can be made more explosive and with more power. Plyometrics is simply a set of drills designed to repetitively stimulate this elastic component over and over again. Remember that if the concentric muscle action does not immediately follow the “pre-stretch,?the potential energy produced by the stretch reflex response is lost. By using a variety of different plyometric exercises, motor performance can be greatly improved.

When first incorporating this explosive style of training in a fitness routine, low intensity exercises should be practiced first before moving onto more intense plyometrics.

Low Intensity Plyometric Exercises:

1. Jumping Lunges ?Stand in a split stance, right leg in front and left leg in back. Bend knees into a lunge (keeping front knee behind toe) and, in an explosive movement, jump up, switch legs in the air and land in a lunge with the left foot forward. Go as slow as you need to to keep your balance. Go faster, jump higher and/or lunge lower for more of a challenge.
2. Leg Raise Throw-Downs ?Lie on your back with your legs mostly straight but with a slight bend, almost perpendicular to the ground. Have a partner push your legs downward while you apply resistance to normalize the speed of descent. Bring your legs quickly back to the original position.
3. Jump Squat ?Stand with your feet shoulder-width apart. Sit back into a squat. Thrust your body up above the starting position. Land with your knees bent to absorb the impact. Reset your body and repeat. Do not hold a squat position before jumping up ?keep the time between dipping down and jumping up to a minimum.
4. Medicine Ball Throws ?This exercise focuses mostly on the core. Tossing a medicine ball to a partner in front of you, to the side, or overhead can help develop the core stabilizing muscles in a way more specific to most sports than basic crunches.

Moderate and High Intensity Plyometric Exercises:

1. Lateral Hurdle Jumps ?Stand beside stacked plyo-blocks. Pull knees upward and jump vertically and laterally off the floor and over the blocks. Land softly on both feet and immediately jump the reverse direction over the blocks to the original starting point. Do not to pause between jumps or bend the knees too deeply. Also maintain an erect torso to prevent lower back strain.
2. Depth Jumps ?Stand on top of stacked plyo-blocks with a slight knee bend and erect torso, with your feet shoulder width apart. Hop off the box into the air in front of the blocks and land on the ground softly with both feet. The goal is not to gain elevation on this initial hop, rather get your body in motion and let gravity take care of the rest. Jump high in the air straight up reaching your arms as high as possible. Spring off the floor backwards onto the box as soon as your feet hit the floor. Regain your balance on the blocks and hop off again.
3. Plyometric Dips ?Stand facing parallel bars or a dip rack. Mount the apparatus by placing your hands on each bar. Push up from the bars until your body weight is supported with your arms straight and shoulders over your hands. Then lower your body until your arms are bent to a 90 degree angle, and then lift your body up with enough force to let your hands come off above the bars briefly. Quickly Re-grab the bar and lower yourself into the next dip.
4. Bounding ?Bounding is basically running with exaggerated strides. The goal is to maximize time spent in the air while minimizing the time that either foot stays in contact with the ground. Bounding can be done on flat terrain, going uphill, up a flight of steps, or even laterally (to the side).

Michael Everts?references for this article include:

1. Essentials of Strength and Conditioning. Human Kinetics ?Baechle, Thomas. Champaign, IL. 1994.
2. Journal of Biomechanics, Volume 33, Issue 10, Pages 1197-1206. Stretch-shortening Cycle: a Powerful Model to Study Normal and Fatigued Muscle. P.Komi.
3. Journal of Sports Science and Medicine (2006) 5, 459-465. The Effects of a 6-Week Plyometric Training Program on Agility.