Concepts of Plyometric Exercise
Plyometric exercise is an essential component to any athlete's
training program. Plyometric training is utilized to increase
explosiveness, vertical jumping, horizontal jumping, speed, and
body awareness. Athletes, regardless of the sport they participate
in will benefit from plyometric training since it increases the
amount of power an athlete produces during athletic performance.
Power is defined as strength x speed. Therefore, an athlete who
trains plyometrics will have an increase production of speed and
strength, resulting in an overall increase in power. Additionally,
plyometric exercises will have a positive affect on athletic
success since the athlete will be trained to create muscular forces
in the quickest amount of time as possible. Whatever the sport,
plyometric training will increase the athlete's production of power
resulting in an increase of over-all athletic performance that
transforms into an increase of athletic success on the playing
field.
How does plyometric training increase the amount of power produced
by an individual? There are two accepted models that explain how
plyometric exercise has a positive correlation with the production
of power. The first model is the stretch reflex response. This
model suggests by applying a rapid stretch during exercise there
will be increase activity in the muscle fibers. The increase
activity in the muscle fibers results in an increase of muscular
force produced by the fibers. For example, a bungee jumper
preparing to leap off a bridge has the ability to create a great
deal of force once a stretch is applied to the bungee rope. The
stretch increases the activity of the cord's fibers, producing
large amounts of force that propels the jumper high into the
air.
Another theory that attempts to explain how plyometric training
increases power is the mechanical model. The mechanical model
simply states that energy is stored in the muscle tendon. Once a
stretch is applied to the muscle tendons and then rapidly released
during a muscle contraction an increase of muscular force
production occurs. The increase in force production is contributed
to the muscles and tendons elastic response to return to their
natural length prior to the stretch. The mechanical model is
similar to a rubber band. Once a stretch is applied to a rubber
band, it creates tension or stored energy, which is utilized to
create a rapid contraction so it may return to its original length.
Even though experts agree that both models have significant
contributions to plyometric training, it is unclear to what
proportions each model has on the effect of power.
While performing plyometric exercise there are three phases that
must be executed that are essential for the production of power.
The first phase consist of a rapid stretch that stimulates muscle
spindles for the purpose of generating additional muscle
contractions, which is called eccentric loading. The eccentric
loading phase is an important component of plyometric training
since both models require a stretch in order for increased muscle
production to occur. The second and most critical phase is
amortization. The amortization phase is the time from ground
contact to the reversal of movement. This phase is the most
important link to the production of power due to the correlation of
duration and power. The shorter the duration of the amortization
phase the greater the increase in power. Likewise, the longer the
duration of the amortization phase, the greater the decrease in
power. The concentric phase is the last phase during plyometric
exercise. During this phase, the stored energy from the eccentric
phase is either used to increase the amount of force produced by
the muscle fibers or released as heat depending on the length of
the amortization phase. Consider the rubber band example used to
describe the mechanical model and apply it to the phases of
plyometric exercise. The application of a stretch to the rubber
band is considered eccentric loading. The amount of time it takes
to stretch the rubber band and the speed, which the rubber band is
released, describe the amortization phase. The concentric phase
consists of the amount of force produced while the rubber band
contracts in order to return to its original length.
Now that there is a basic understanding of the physiology of
plyometric exercise, there are several guidelines that need to be
addressed before an athlete begins training. Firstly, the athlete
must be able to squat a minimum of fifty percent of their body
weight and at least 200 percent for more intense exercises. If the
athlete does not have enough strength to meet the squat
requirement, then emphasis should be placed on a strengthening
program rather than plyometric exercise in order to prevent
injuries. Always utilize non-slip surfaces to avoid falling or
slipping accidents. Provide an appropriate warm-up that increases
the heart rate and prepares the body for high impact exercise. For
example, ladder agility drills, skipping, bounding and hopping
adequately warms up the body while preparing the body for
plyometric training. Never perform plyometric exercises on heavy
lifting days since muscle fatigue may increase the potential for
injuries to occur. Box jumps should not be performed if they
displace the center of gravity more than eighteen inches for a two
hundred pound athlete for safety concerns. Following these
guidelines will ensure a safe environment for the athlete while
performing plyometric exercises and assist in preventing
injuries.
Another important concept to understand is the progression of
plyometric training. The proper progression of plyometric exercise
will maintain proper body mechanics, increase body awareness and
prevent injuries. Plyometric training utilizes foot strikes (fs) to
measure the amount volume per exercise. Generally three sets of
foot strikes are performed for each exercise. The typical volume of
exercises is generally recommended: beginners 50-100 fs,
intermediate athletes 100-200 fs and advanced athletes 200-400 fs.
On the other hand, the intensity level of the exercise inversely
affects the level volume; the greater the intensity signifies a
decrease in volume. Allowing adequate rest cycles between sets is
necessary for the athlete to perform plyometric exercises at
maximal intensities; however, this is a subjective measurement and
usually ranges between thirty seconds and three minutes. Plyometric
training should always begin with low intensity exercises while
gradually increasing to high intensity exercises so proper body
mechanics are maintained to avoid injuries. The recommended
progression for plyometric exercise is as follows: standing
vertical jumps, standing horizontal jumps, standing lateral jumps,
multiple jumps, bounding, box jumps and depth jumps. Lastly,
provide appropriate recovery time, generally forty-eight to
seventy-two hours or merely perform plyometric training once a
week.
In conclusion, plyometric exercise is an effective tool to increase
power, resulting in enhanced athletic performance. The stretch
reflex model and the mechanical model explain the physiology of
plyometric exercise and demonstrates how the athlete achieves
increased power production during training. The three phases of
plyometric training provide the essential components necessary
during plyometric exercise in order to experience increased power,
resulting in enhanced performance levels. By adhering to the safety
guidelines while performing plyometric exercises the athlete will
be in a safe environment that will decrease the chance of injury.
Progressing the athlete through pylometric training is an essential
aspect that will further increase sport enhancement if conducted in
a safe and logical manner. Plyometric exercise provides the results
that athletes are searching for in order to be successful during
competition.
Article Contributed by
Shawn Garlock, ATC