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Plyometrics: Developing Power in Everyday Athletes

National Academy of Sports Medicine
National Academy of Sports Medicine
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Power is the ability to quickly produce large amounts of force. Are there any athletes that would not want to improve their ability to generate power?

Conditioning Coaches who want to give their athletes some added explosiveness? What about clients seeking to improve general fitness? Power is essential for all three groups. By incorporating plyometric exercises into training programs, the speed and force of movement can be harnessed for improved performance and daily activities.

What are plyometrics?

Power training is synonymous with the explosive movements of plyometric training. Plyometrics is built upon various scientific principles (stretch-shortening cycle; optimizing sarcomere length, and stretch reflexes to a lesser degree) that can help individuals tremendously boost their power output (1, 2).

Although plyometric training can add a fun and challenging component to training programs, like most, it must be introduced, coached, and progressed systematically in order to avoid injuries.

Although jumps in place (e.g., jumping jacks) and box jumps are relatively easy to perform (just avoid catching your shins on the boxes).

It is bounding (single-leg take-off, opposite leg-landing), hops (single-leg take-off, same leg-landing), and depth jumps (e.g., dropping off elevated platforms, absorbing impact forces eccentrically, then exploding concentrically) that demand a solid foundation of joint integrity, strength, flexibility, and technique to avoid injury.

The 3 Phases of Plyometric Exercises

Plyometric exercises have three distinct phases, an eccentric phase, an amortization phase, and a concentric phase that releases the explosive force. These three phases make up a stretch-shortening cycle.

Eccentric Phase

During the eccentric phase, the muscle is prestretched, storing potential energy in the elastic components of the muscle (1-3). The eccentric phase has also been referred to as deceleration, loading, yielding, or the cocking phase (1-2).

When basketball players bend their knees and lower their arms before a rebound shot or when a baseball player pulls his arm back before a throw to first base are both examples of the eccentric phase.

Amortization phase

The amortization phase is a time of dynamic stabilization during which the muscle transitions from loading the energy to releasing it. If this phase lasts too long, the potential elastic energy can be lost. The shorter the amortization phase, the more powerful the results.

Concentric Phase

Unloading the energy occurs next in the concentric phase, adding to the tension generated in a concentric muscle contraction. This is where the athlete releases the stored and redirected energy, jumping for the basket or slinging the ball to first base.

Using the OPT Model for Plyometrics

Before incorporating plyometric exercises, athletes and clients alike must have the ability to balance efficiently, and possess adequate core strength, joint stability and range of motion. Plyometric drills may not be suitable for those with chronic or limiting conditions (1,2).

Following the NASM Optimum Performance Training ™ (OPT™) model, plyometric exercises progress from stabilization (e.g., squat jump with a 3-5 second stabilization hold on landing), to strength (e.g., tuck jump), then to power (integrated, functional movements performed at a quick tempo such as ice skaters) (1,2).

Plyometric exercises aren’t limited to the lower body. There are upper-body activities, including plyometric push-ups, wall throws, overhead throws, or combination moves such as a jump squat with a chest pass.

The benefits of plyometrics

Of the many benefits of plyometric training, some of the more recognized are:

  • increased vertical jump height
  • long jump
  • strength
  • improved running speed
  • injury prevention

It’s probably easier to see how plyometric training can be used to improve athletic performance, but perhaps more difficult to see why plyometric exercises would benefit the non-athlete.

Plyometrics is interchangeably termed reactive training. From this perspective, it is essentially about how the body interacts with ground surfaces. Being able to quickly respond to an unexpected change in surface when stepping off a curb, or to rapidly change direction when walking a dog on leash are possible examples clients may encounter (1,5).

Begin with activities that focus on plyometric stabilization exercises, even using regressions such as step-up/step-down or step-up/step-down to the front on a low box or bench.

Reminder about the 3 phases

Recall that plyometric exercises are based on three phases, an eccentric phase that stretches the muscle, the amortization phase focusing on dynamic stabilization, and the concentric phase that concentrically contracts the muscle.

Many exercises are secretly plyometric exercises if they incorporate explosive moves. Progress plyometric exercises safely by going from easy to hard, simple to complex, known to unknown, stable to unstable, body weight to loaded, or activity specific (1,2).

Plyometric Programs 101

Plyometric programs are generally developed and progressed consistent with skill-level or mastery, exercise choice, but most importantly volume. Volume is determined by the number of foot contacts (e.g., each time you land = 1 foot contact), or upper-extremity contacts completed (e.g., each time you throw a ball = contact) (Table 1-1).

catching more air1

Regardless, training good form with inexperienced individuals or allowing adequate dynamic warm-up with more experienced individuals to reinforce good mechanics, are critical to success and avoiding injury.

Using the lower extremity as an example, when designing plyometric programs, plan to train no more than two to three times per week, with only one day being devoted to high-intensity drills like bounding, hopping or depth jumps.

Use lower-intensity drills (e.g., jumps-in-place, single linear jumps like one plyo box jump) and moderate intensity-drills (multi-directional jumps or multiple linear jumps like a continuous set of plyo box jumps for 10 seconds) as part of your warm-up, or as exercises more frequently throughout the week.

How to teach good plyometrics form

The coaching fundamentals used in teaching good form begin with first instructing jump-landing mechanics and progressing the program only when form mastery is exhibited. Some coaching tips to improve jump-landing mechanics include:

Stage One

Instructing individuals how to properly hip-hinge from a standing position using a dowel or light bar and maintaining good spinal orientation as the body hinges and lowers (i.e., 3 points of contact with the bar – sacrum, thoracic spine and back of the head).

  • This movement, versus a more quad-dominant lowering position reduces knee and hip shearing forces, while also loading (eccentrically) the gluteus maximus to facilitate a more powerful unloading (concentric contraction) during the triple extension phase (ankle, knee, and hip).

Stage Two

Introduce more dynamic movement from standing with a hip-hinge to triple-extension (end point on toes) movements and introduce arm swings (i.e., shoulder flexion and extension).

This helps cue the mid-foot strike, rolling backwards into the heels and absorbing impact forces into the soft (elastic) structures rather than the bony structures.

  • Progress by gradually lowering the body further towards the ground while cuing knee alignment over the toes and under the anterior superior iliac spine (ASIS). During periods of greatest instability in jumping (i.e., the landing instant and the instant of initiating the concentric phase), monitor knee alignment as these two times represent the greatest likelihood for valgus movement (i.e., knees collapsing inward).
  • When ready, begin coaching your athletes to reduce the amortization phase or transition between the lowering and rising phases in order to harness elastic energy into motion (minimizing potential energy leaks).
  • Emphasize upper extremity alignment and head position (eyes-ups, head aligned with spine) using cues like nose-over-toes or chest-over-knees at the bottom of eccentric loading phase.

Stage Three

Progress to in-place single squat jumps emphasizing small vertical take-offs and good landing mechanics.

  • Land softly with mid-foot, rolling backwards smoothly.
  • Cue knee alignment during periods of greatest instability.
  • Cue upper extremity alignment throughout this more dynamic movement.
    • Visual feedback (e.g., mirrors or video) and self-evaluation are excellent tools to utilize to increase awareness of misalignments. For example, facing a mirror and freezing just before, and just after, the amortization phases allows the individual to examine their knee alignment. Likewise, from a side view, freezing at those same instants allows the individual to examine their spinal and head alignment.

Stage Four: Introduce multiple jumps using agility ladders.

  • Cue individuals to perform sequences of repeated jumps through the agility ladder squares, emphasizing technique while moving forward.
  • The individual squares within one ladder or using ladders orientated in different directions provide excellent spatially-defined targets for coaching sagittal, lateral, rotational and even multi-directional jumps, bounds and hops.
  • However, it is important to keep in mind that the ladders do not challenge vertical explosiveness, therefore your goal should be progress out of the ladders to clearing taller obstacles or landing on boxes. Furthermore, sports and life rarely offer such clearly-defined landing targets, so move away from them when possible.

In closing, while plyometrics can be fun, take the needed time to first prepare the body physiologically. Develop your systematic plan to advance individuals towards higher-intensity drills once they demonstrate technique mastery and can adequately tolerate jump-landing forces.

Before long, they might just be on their way to achieving impressive feats like what JJ Watts makes look so easy.

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Sources

  1. Clark, MA, Lucett, SC, Sutton, BG. NASM Essentials of Personal Fitness Training 4th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2012.
  2. Clark, MA, Lucett, SC. NASM Essentials of Sports Performance Training. Baltimore, MD: Lippincott Williams & Wilkins; 2010.
  3. Chu, DA. Jumping Into Plyometrics 2nd ed. Champaign, IL: Human Kinetics; 1998.
  4. Fleck, SJ, Kraemer, WJ. Desgining Resistance Training Programs 2nd ed. Champaign, IL: Human Kinetics; 1997.
  5. Rose, DJ. Fall Proof! A Comprehensive Balance and Mobility Training Program. Champaign, IL: Human Kinetics; 2003.
  6. Chu, D and Myers, GD. Plyometrics: Dynamic Strength and Explosive Power. Champaign, IL. Human Kinetics (2013).
  7. Yessis, M. Explosive Running: Using the Science of Kinesiology to Improve Your Performance (1st Edition). Columbus, OH. McGraw-Hill Companies. (2000).
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National Academy of Sports Medicine

National Academy of Sports Medicine

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