IMPROVE YOUR SPORTS PERFORMANCE WITH PLYOMETRIC TRAINING

In athletic performance, when muscles are stretched immediately prior to contraction, they are capable of producing greater forces.

• Throwers move in a way that stretches the chest muscles just prior to the throw. This stretching of the chest muscles increases their ability to speed up the implement.
• In the jumpers, when the foot contacts the ground, allow the leg to flex slightly, allowing the extensor muscles to stretch and the leg to operate like a spring.

Muscles and the associated connective tissues are at their best when they are allowed to stretch and snap back like rubber bands. We call the body's reaction to this stretching with these increases in force production, a stretch reflex. The physiological response associated with it is called an elastic response. This response is also commonly called a stretch-shortening cycle (SSC) in the literature. The additional performance boost gained when muscles operate this way is called elastic energy, and the production of elastic energy is the key to high levels of performance in nearly all sports endeavors. Sports training that uses and improves elastic energy production is called plyometric training.

Many persons think of plyometric training as jump training. However, many other forms of training are plyometric in nature as well. For this reason, to clarify our terminology, in this post we'll use the term multijump training to define jump training designed to improve the elastic response, and we'll consider multijump training as a subset of plyometric training.

Key plyometric training terms:

• Stretch reflex
• Elastic response
• Stretch-shortening cycle (SSC)
• Elastic energy
• Plyometric and multijump training

We do multijump training for two purposes:

1. First of all, this training of the elastic response improves an athlete's power and elastic strength capabilities. This results in a stronger athlete who can jump better and move faster. 
2. Secondly, multijump training develops an athlete's ability to apply force as well in specific plains and directions. This results in improved running mechanics, improved jumping mechanics, improved throwing mechanics, and generally improved quality of movement.

Competitions are intense and explosive, so multijump training is very specific and improvements here show great skill transfer into the sports themselves.

Purposes of multijump training:

• Development of power and elastic strength
• Improved mechanics and skill transfer

While certain forms of multijump training can be done even by athletes of the earliest developmental stages, high level multijump training is a high risk and high reward type of activity. For this reason, we'll define these key rules governing multijump training:

• First of all, multijump training should be well planned.
  • Volumes and intensity should be appropriate to the athlete's age, experience level, and the time of the training year.
  • Multijump training should progress properly throughout the entire training calendar in a way that increases intensities in a safe, progressive manner. Long-term and short-term planning are a must.
• Secondly, multijump training must be purposeful. Each type of multijump exercise has a certain purpose and role in the training program, and it should be used for that purpose only and only at times of the year when that purpose is appropriate. Many injuries result because coaches mindlessly repeat multijump routines throughout the year without considerations of their training effects.
• Finally, to minimize the risk of injury, multijump exercises must be taught correctly and executed with correct technique at all times. Some forms of multijump training are far more difficult and technical than others.

Rules governing multijump training:

• Must be well planned
• Must be purposeful
• Must employ correct techniques

There are three distinct phases that the jumping leg goes through in any multijump exercise:

1. Just prior to the foot contacting the ground, the muscles of the leg contract isometrically, stiffening the leg in anticipation of impact and improving the quality of the elastic response yet to come. We call this the preparation phase.
2. Upon impact, the leg flexes and gives a bit allowing elastic responses to occur in the extensor muscles. This is called the amortization phase.
3. Finally, the leg extends using the concentric contraction to propel the body into flight.

Phases of the elastic response:

• The preparation phase - Leg muscles contract isometrically to brace legs in anticipation of impact.
• The amortization phase - Upon impact, the legs flex, stretching the leg extensor muscles and creating a stretch.
• The extension phase - The legs extend, propelling the body into flight.

The takeoff leg goes through these three distinct phases in a fraction of a second in all jumping activities, and good plyometric teaching addresses all of these phases.

In particular, the isometric preparation prior to impact should be emphasized in teaching, by teaching correct positions of the leg, particularly the positions of the ankle.

Also, the ground contact time used to convert from the amortization phase to the extension phase is unique to each athlete in each exercise. In most cases, athletes will tend to spend too much time on the ground, and their training must center about improving the preparation phase and lessening the ground contact time. However, a small amount of time to convert from eccentric to concentric is necessary, and occasionally you'll find an athlete who is actually too stiff and generailly needs to spend a little more time on the ground. Ground contact time is not to be minimized or maximized, but optimized, and teaching good technique will result in proper ground contact times.

• Teaching body positions prior to impact is especially important, since it assures a good preparation phase.
• Ground contact times are unique to each situation and should be optimized.

Generally speaking, multi-jump technique concerns fall into three categories:

1. First of all are the ground contact skills: the proper execution of the preparation, amortization, and extension phases.
2. Secondly, we must be concerned with posture: proper stabilization and alignment of the body's core in order to maximize performance and minimize injury risk.
3. Finally, most multijump exercises show swinging movements of the arms. In single leg jumping the free leg swings as well. These swinging movements must be executed correctly in order to maximize force production and in some cases to maintain good posture.

Multijump technical concerns:

• Ground contact skills - Ground contact skills must be taught.
• Posture - Postural skills must be taught.
• Swinging movements - Swinging segment skills must be taught.

Next, we will analyze hurdle hops as an example of a plyometric exercise.

Hurdle Hops

Like vertical bounds, hurdle hops are vertically directed jumps that are technically specific. Being technically specific means that forces are applied in these bounds in a way that greatly resembles the way vertical forces are applied in sports performance. For instance, during maximal velocity sprinting, forces applied to the ground are aligned in a predominantly vertical direction, so these exercises help to improve sprint mechanics and other forms of movement quality. The foot contact patterns are similar to sprinting as well. They are of moderate to high intensity and almost always use double leg takeoffs.

Hurdle hops:

• Vertical, repetitive jumps
• Technically specific
• Moderate to high intensity
• Double legged

Because of these characteristics, hurdle hops should be used when we want to develop power and elastic strength in a moderate to advanced way, and improve technique and movement quality in a vertical sense.

The purpose of hurdle hops:

• Moderate to advanced level power and elastic strength development
• Technical improvements in vertically based skills

Good hurdle hop series can use a single or multiple forms of hurdle hopping. Use only 4 to 6 hurdles. This ensures fatigue won't set in during the set and that technique won't break down at the end of the set as a result. Hurdle spacings will vary depending upon the athlete and the type of exercise they're doing. You'll have to experiment, but be cautious and keep it safe. Compensate for the small number of hurdles with large numbers of sets. Do enough sets to get 24 to 48 total takeoffs. This might not sound like much, but hurdle hop routines should be based on quality, not quantity.

Hurdle hop session design guidelines:

• Single or multiple forms of hurdle hopping
• 4-6 hurdles
• Spacings vary depending on the athlete and the exercise - Experiment cautiously
• 24-48 total takeoffs

The content of this article is based on the introduction of the plyometric training program designed by Boo Schexnayder, applicable to any sport. Within it you will find the following information: how to implement it with correct set/rep schemes, how to teach it with technical teaching cues, writing plyometric workouts, injury prevention, and much more.

Bibliographic references:

• CompleteTrack. (2016). Plyometric Training for Sports Performance [Video file]. YouTube. https://youtu.be/fqI_eWMjB8M?si=_sswia2IEWgSY-3T
• CompleteTrack. (2017). Hurdle Hops: Purpose and Programming [Video file]. YouTube. https://youtu.be/s3V7B2EwwM4?si=XMFtYiMpUT3TQaah