Chapter 14 Plyometrics in Rehabilitation

After studying this chapter, the reader will be able to do the following:

1. Understand the physiology of plyometric exercises

2. Design a functional progression of plyometric exercises

3. Determine the physiological requirements before starting a plyometric exercise program

4. Determine the importance of posture and jumping techniques in plyometric exercises

5. Identify the landing strategies in plyometric exercises

6. Design a plyometric training program

7. Integrate foot work into speed development programs

8. Give objectives for jumping patterns

9. Understand how to progress an athlete in work, intensity, and volume

Plyometric exercises are often included in rehabilitation programs to prepare athletes for the demands of their sport and a safe return to play. In a clinical setting, care plans are often developed on the basis of sound principles, such as functional progressions; SAID (s pecific a daptations to i mposed d emands); and manipulating routine variables ([FITTR] f requency, i ntensity, t ime/duration, t ype/mode, and r ate of progression). Progression from rehabilitation to performance conditioning for the injured athlete should be no different. The effectiveness of a plyometric workout should not be measured by “how tired” an athlete feels. It should focus on the “quality” of the movements. The “exercise-to-fatigue approach” may lead to overtraining, exercise-related pain, and even overuse injuries. Structure and accountability are necessary when including plyometric exercises in rehabilitation and strength and conditioning programs including progression in work volume and intensity.

FUNCTIONAL PROGRESSION

In Review

Functional progression is a series of basic movement patterns graduated according to the difficulty of the skill and an athlete’s tolerance.¹ The primary objective of functional progression in rehabilitation is an athlete’s timely and safe return to competition. From a prevention standpoint, it is the optimal preparation for the specific demands of a sport. At the heart of functional progression is the SAID principle (specific adaptations to imposed demands), which simply means that physical activities should be appropriate and strategic in preparing an athlete for the demands of his or her sport including such components as acceleration/deceleration of movement, specific velocities of movement, planes and ranges of motion, varied degrees of dynamic trunk stabilization, and coordinated whole body patterns of movement.

Tippett and Voight ¹ provided guidelines governing the advancement of a functional progression program:

• Begin with static positions and progress to movement.

• Initiate skills at a slow speed and progress to faster speeds.

• Initiate skills that are simple and progress to more difficult skills.

• Initiate skills unloaded (bodyweight only) and progress to loaded (resisted) skills.

In this chapter, emphasis is placed on cardinal plane maneuvers performed in one place or covering short distances, or both, including 2- and 1-leg squatting, step-ups, and various jumping exercises, such as the four-square and staggered-ladder patterns. In these exercises the athlete moves within a cardinal plane or planes when traveling forward/backward. Movements in a sagittal or frontal plane occur with exercises, such as left-to-right jumps over a barrier. For the purposes of this chapter, these exercises are examples of simple skills that are building blocks in preparing an athlete for more difficult skills, such as running with quick starts and stops, changes of direction within varied sport-specific distances, and simulation of gamelike activities.

Following is an example of how to apply functional progression guidelines and graduate an athlete from one basic skill to the next. Two points on the exercise progressions are important to note:

1. The athlete learns to attain alignment and postural control before advancing to the next phase (i.e., static control in a squat position, followed by adding a dynamic movement).

2. The athlete develops strength to maintain proper alignment, which builds a stronger base for dynamic actions (i.e., landing strategies before jump patterns).

The exercises should progress in the order listed:

1. Strength phase: Static squat-to-adding movement, two-leg squat to one-leg squat on bench, and forward/back (FW/BK) step-ups to lateral step-ups.

2. Plyo-support^* phase: Landing strategies with simulated jump patterns.

3. Performance phase: Jump patterns as follows:

FW/BK jumps and left/right jumps

Add diagonals in four-square formations

Staggered-ladder formation—progressive locomotive patterns

Two-leg to one-leg jumps in patterns mentioned previously

In Figure 14-1, B a dowel is used as a cue for proper alignment from the head/neck, trunk, and low back/pelvis. In a squatting posture the spinal curves should change and adjust to the anterior tilt of the pelvis. As the pelvis tilts forward, the lumbar vertebrae are forced anteriorly, thereby increasing lumbar concavity (lordotic curve). The line of gravity (LOG) therefore is at a greater distance from the joint axes of the spinal segments, and the extension moment is increased at both the cervical and lumbar regions. The posterior convexity of the thoracic curve increases slightly and becomes kyphotic in order to balance the greater-than-normal lordotic lumbar curve. Referring to the dowel, the contact points of the body along the dowel are at the head, a midpoint along the thoracic spine, and base of the lumbar spine-pelvis, which assists the athlete in maintaining the three adjusted spinal positions—increased cervical, thoracic, and lumbar curves that accompany an increased anterior pelvic tilt. Figure 14-1, C also demonstrates the correct posture for the “freeze” positions, which are discussed later in the section on landing strategies. Therefore as an athlete jumps forward/back and “freezes,” he or she needs to land while maintaining this posture. By maintaining the anterior pelvic tilt and proper curves of the spine and not flexing at the head/neck and trunk or losing lumbar lordosis, the athlete will be in the most effective position for subsequent takeoff. This is an example of dynamic postural control training, which is part of the plyo-support phase following the development of an adequate strength base.

Figure 14-1 A,“Forward head” and “rounded shoulders” posture, which can increase ground contact time during landing due to the time needed to extend the spine before changing directions.B, A dowel is used as a cue for proper alignment from the head/neck, trunk, and low back/pelvis. C, The correct posture for the “freeze” positions described in the Landing Strategies section.

PLYOMETRIC IN NATURE

The practical definition of plyometrics is a quick, powerful movement involving prestretching or countermovement that activates the stretch shortening cycle (SSC) of muscle.² Within this powerful movement is an eccentric phase or force reduction phase; amortization phase or transition moment involving dynamic stabilization; and concentric phase or force production phase.³ Although it is common to view plyometrics as a by-product of muscle activity alone, the nervous system must be considered as well. Ultimately, the purpose of plyometric conditioning is to heighten the excitability of the nervous system for improved reactive ability of the neuromuscular system as a whole.² If one considers the parameters that go into describing a plyometric exercise including the use of the stretch reflex and taking advantage of the elastic rebound tendency of muscle tissue, then the definition can be broadened to include many exercises that are “plyometric in nature.”⁴

The term plyometrics has been broadened to mean many different activities, from depth-jumps using a 48-inch box to aerobic dance exercise. Some aquatic programs even refer to certain exercises as being plyometric. Plyometrics, in its purist form, is meant to encompass maximal, all-out, quality efforts with gravity and body weight being the constants for each repetition of an exercise. This said, certain populations benefit from lower-intensity exercises that are plyometric in nature and performed with submaximal efforts. These include younger (prepubescent and adolescent) athletes and those recovering from injury. Younger athletes may lack the strength base or physical maturity to undergo the rigors of a maximal effort plyometric workout and would benefit by performing lower-intensity exercises designed to improve movement (kinesthetic awareness and body control). Athletes recovering from injury are involved in reestablishing the neural patterns and muscular reactivity that will allow them to perform at a higher level without the risk of reinjury or additional trauma. The nature of these exercises can definitely qualify under the heading of “plyometric in nature.”

INTENSITY AND WORK VOLUME

Strategic and Appropriate: More Is Not Better!

The term plyometric is from the Latin plyo + metrics and is interpreted to mean “measurable increases.” Inappropriate applications of plyometric exercises can happen if not monitored correctly. Part of the proper practice of using plyometrics is to simply measure performance and have a plan. In other words, if a scheduled workout has assigned 80 total foot contacts (2 exercises, 2 sets × 20R each exercise), the athlete is finished with the plyometrics portion of the session once that work is completed. An increased risk of overtraining and exercise-related injuries occurs when plyometric work is not measured and progressed appropriately, especially if a therapist, coach, or athlete uses a “feel-the-burn” approach and measures success by “how tired” he or she feels following the workout. When considering the workloads for those athletes who are rehabilitating from a lower extremity injury, the therapist must understand that, no matter their skill level, they are to be considered “beginners” at the high-end (final stages) of their rehabilitation. Their progress is merely on a longer continuum as compared with the noninjured athlete.

Table 14-1 adjusts work volume (total foot contacts) and intensity on the basis of seasonal periods and an individual’s “readiness for plyometrics.” The recommended volume of specific jumps in any one session will vary with intensity and each workout’s objectives. Table 14-1 shows how work volume should vary for beginning, intermediate, and advanced workouts.⁴ For example, a beginner in one workout during the off season could complete 60 to 100 foot contacts of low-intensity exercises, while the advanced exerciser might be able to do 120 to 200 foot contacts in one off-season workout. With low-intensity jump training, the work volume accumulates quickly. Note that an athlete performing two sets of each of the following exercises will complete 280 foot contacts in one workout using the four-square formation (Figure 14-2).

Table 14-1 Total Foot Contacts Based on an Athlete’s Level and Seasonal Periods

Figure 14-2 Four-square pattern. Sample “triangle” pattern (1, 2, 3). Count 1R each time the athlete hits “1.” Following 20R, the athlete will then perform the opposite triangle pattern (4, 3, 2) for 20 R.

• 1,2 × 10 reps (2 foot contacts each repetition [rep], or 20 foot contacts per set)

• 2,3 × 10 reps (20 foot contacts per set)

• 1,2,3 × 10 reps (1 rep = 3 foot contacts, or 30 foot contacts per set)

• 4,3,2 × 10 reps (1 rep = 3 foot contacts, or 30 foot contacts per set)

• 2,1,3,4 × 10 reps (1 rep = 4 foot contacts, or 40 foot contacts per set)

Consider: 1 set of each exercise above = 140 foot contacts, 2 sets = 280 foot contacts.

Considering the cumulative effect on work volume when combining low- and high-intensity exercises during “preseason” workouts for both intermediate- and advanced-level athletes is important. If an athlete at either level has a scheduled plyometric workout that includes 300 total foot contacts, the previous example of 280 foot contacts of low-intensity jumps using a four-square formation would only allow room for 2 sets of 10 reps of a high-intensity exercise, such as depth jumps. The proportion among low-, moderate-, and high-intensity work would depend on the objectives of the program and objectives of each session within a periodized (cycled training) model. Periodization is a method that divides the training year into specific phases, such as preparation, precompetition, competition, and transition phases. A schedule of periodization allows athletes to prepare for peak performance when they need it most, such as a qualifying event, competition, or competitive season. Once again, reiterating the importance of “measurement” and accountability, a therapist or strength and conditioning coach who carefully monitors work volume within his or her athletes’ programs will be able to make more objective decisions regarding progression or even tapering work when necessary, following a periodized model. In addition to work volume, the frequency of plyometric work and recovery between sets are factors to measure and monitor as part of an objective-based strategic plan.

FREQUENCY AND RECOVERY

Allowing 48 to 72 hours between low-intensity plyometric sessions will ensure that adequate rest occurs and the athlete is ready for the next plyometric workout. For example, a common weekly schedule could include the submaximal jump patterns on lower-body strength days, such as Tuesday and Fridays, with upper-body sessions on Monday and Thursdays. An athlete might use a higher frequency (three to four times per week) of plyometric sessions if the exercises used are low in intensity (submaximal) efforts and volume (i.e., three to four exercises of low-intensity, “plyometric in nature” drills employed as part of a warm-up routine).

Adequate recovery between each set in a workout is equally as important as adequate rest between workouts. A common work-to-rest ratio is 1:5 (e.g., an exercise that takes 10 seconds to perform would have 50 seconds rest between sets). An important point to consider with low-intensity plyometric exercises, particularly the footwork patterns presented in this chapter, is that they are “submaximal” in nature. With this in mind, fatigue should not be a factor with this type of work. As stated earlier and also later in this chapter, proprioception, postural control, and dynamic stabilization are points of emphasis with this mode of exercise. Again, fatigue should not be an issue if an athlete follows a course of progression including development of an adequate strength base (i.e., squats and step-ups) and practices landing strategies with adequate body control before performing actual working sets of low-intensity jump training. An athlete will not reach a fatigue state given the submaximal intensity, short duration of activities, and appropriate work-to-rest ratios. As mentioned earlier, submaximal footwork patterns/jumps are often used as part of a warm-up in preparation for moderate- and high-intensity plyometrics.⁴ Otherwise, they can be placed toward the end of a workout, following the primary work of the day (weight training, sprinting, and agility drills).

SAFETY CONSIDERATIONS

Low-intensity plyometrics should be performed in areas that allow both adequate space and a yielding training surface. Multipurpose rooms (e.g., group fitness classrooms), gymnasium floors, and outdoor fields are common places for performing footwork patterns. As in moderate- and high-intensity plyometrics, submaximal jump patterns should not be performed on cement or slippery surfaces.

Although it is common to use athletic or duct tape to set up the four-square and staggered ladder patterns discussed in this chapter, ladders may be preferable for the following reason. Ladders are portable and easy to set up, and they allow for consistency in the dimensions of the patterns. The foam ladders shown in this chapter are “foam ladders,” which adds to performance safety should an athlete not clear the lines and land on the ladder. Another safety point is to use foam barriers, which are less likely to cause injury if landed on. In this chapter, 2-, 4-, and 6-inch foam blocks are used in the four-square and staggered ladder patterns shown.

Allowing time for an adequate warm-up is another important safety consideration in preparing for low-intensity jump training. “Jump rope” is one simple way to prepare for the low-intensity jump patterns, for example:

1. Jump rope 2 minutes. Perform 2 3 bouts with 60 seconds of dynamic stretching between bouts.

2. Dynamic stretching can include multidirectional lunging and standing quadriceps/hip, hamstring, and lower leg stretches.

READINESS FOR PLYOMETRICS

Medical and Orthopedic Considerations

Preexisting medical conditions need to be considered before beginning a plyometric program, particularly with adult and pediatric populations. For the collegiate and professional athlete, certain conditions, such as diabetes or a current viral illness, can have a significant detrimental effect on performance and recovery. With this in mind, it is important to keep an athlete’s relevant-past medical history on file and current health status because it may be necessary in some cases to obtain formal medical clearance before starting the program.

Important orthopedic factors to consider when designing a specific conditioning program using plyometrics include age, gender, and physical maturity and experience level. What is appropriate for one 15-year-old may not be for another. For example, structural and physiological factors may predispose adolescent females to exercise-related pain or injury.

Any preexisting injury would have an important influence on the appropriateness of a plyometric program. For example, deep squats and resisted knee extension may be contraindicated in patients with significant patellofemoral symptoms. For some patients, specific strength training may be necessary before beginning a specific plyometric program, such as hamstring and triceps surae (gastrocnemius-soleus complex) strengthening and co-contraction strategies for patients with a history of anterior cruciate ligament insufficiency. Likewise, athletes who have undergone previous surgery may have specific contraindications or require special areas of emphasis.

At this point, emphasizing a crucial piece of the puzzle in successful plyometric training is necessary. Eccentric strength, or the ability to control the lengthening of a muscle under tension, is vital to becoming faster and jumping higher.⁵ When the force exerted on a muscle exceeds the force developed by the muscle, work is done on the stretching muscle and in the process the muscle absorbs mechanical energy. If this energy is dissipated as heat, the muscle is acting as a shock absorber. If the temporarily stored energy is recovered as elastic recoil energy, it results in a muscle that then shortens in a concentric muscle contraction. This is known as the stretch-shortening cycle (SSC), and it results in improved economy of movement through a significant enhancement of the power output of subsequent contractions. In this way the muscles of the lower extremities are behaving as springs that cyclically absorb and recover elastic recoil energy. The other fundamental facts surrounding eccentric contractions are that the energy costs are unusually low and the magnitude of the force produced is unusually high. Therefore resistance training to improve eccentric strength is important to prepare the muscles and tendons for the stress and strains encountered in plyometric training.⁶ The better prepared the muscles are in this area, the bigger the shock absorbers. Eccentric exercise performed as a regular part of the preparation of the athlete or as part of his or her rehabilitation program requires minimal energy/oxygen support and will increase strength and power in all individuals. The conclusion to be reached is that eccentric strength training should be part of all rehabilitation programs, as well as all performance-enhancement programs.

Body weight and strength ratios are also important factors to consider when initiating plyometric training. For instance, it is suggested for an athlete to be able to perform a back squat with 1.5 times his or her bodyweight (1RM) before beginning high-intensity plyometrics, such as depth jumps.⁴ This can be a dilemma for a high school athlete who could otherwise benefit from a plyometric program but lacks this type of strength due to a lack of maturity or training background. When an athlete is running, he or she is already imposing up to three times his or her body weight in forces through the knees. Without the time, maturity, and preparation to obtain these types of strength levels, what alternatives might exist? As stated earlier, low-intensity plyometrics, such as submaximal footwork patterns, are a healthy alternative for young athletes who lack an adequate strength base to perform high-intensity plyometrics.⁴ Continuing with the adolescent or prepubescent athlete as an example, the submaximal footwork patterns will teach a young athlete to control his or her center of gravity, land softly, change direction quickly, and spend as little time on the ground as possible. Low-intensity plyometrics can then be viewed as support work for healthier training in young athletes when combined with body weight resistance strength work and landing strategies, as well as development of eccentric strength.

Low-intensity plyometrics are also a healthy choice for larger athletes, such as those weighing more than 220 lb. For a tall, 260-lb basketball player, the four-square drill can be viewed as a dynamic ankle stabilization exercise and combined in a lower-leg circuit including wobble-board, “Bosu ball,” or “Dyna-disk” exercises along with resisted dorsiflexion, eversion, and inversion of the ankle movements with a resistance band. In this case submaximal footwork patterns that are plyometric in nature are a healthy alternative for a heavier athlete, in whom high-intensity plyometrics may be contraindicated due to body weight and sport demands (e.g., basketball, a sport that innately includes high-volume/high-frequency jumping through a long season).

The concept of developing the base of strength within an athlete must never be lost during the training process. The types of strength necessary to improve or maintain performance can only be developed through adequate, monitored, and challenging resistance training programs. The fact that free weight lifting provides the exerciser with the resistance necessary to create greater force production, potential for power development, and faster speed of movement is a well-established concept. These movements are integral to the “functional training” or “sport-specific” philosophies followed by therapists and strength and conditioning coaches today. The following strength training exercises are examples of the progressive sequence that should be typically followed as one prepares to undergo the rigors of plyometric training.

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