Speed and strength are integral components of
fitness found in varying degrees in virtually all athletic movements.
Simply put the combination of speed and strength is power. For many years
coaches and athletes have sought to improve power in order to enhance
performance. Throughout this century and no doubt long before, jumping,
bounding and hopping exercises have been used in various ways to enhance
athletic performance. In recent years this distinct method of training for
power or explosiveness has been termed plyometrics. Whatever the origins
of the word the term is used to describe the method of training which
seeks to enhance the explosive reaction of the individual through powerful
muscular contractions as a result of rapid eccentric contractions.
Muscle Mechanism
The maximum
force that a muscle can develop is attained during a rapid eccentric
contraction. However, it should be realized that muscles seldom perform
one type of contraction in isolation during athletic movements. When a
concentric contraction occurs (muscle shortens) immediately following an
eccentric contraction (muscle lengthens) then the force generated can be
dramatically increased. If a muscle is stretched, much of the energy
required to stretch it is lost as heat, but some of this energy can be
stored by the elastic components of the muscle. This stored energy is
available to the muscle only during a subsequent contraction. It is
important to realize that this energy boost is lost if the eccentric
contraction is not followed immediately by a concentric effort. To express
this greater force the muscle must contract within the shortest time
possible. This whole process is frequently called the stretch shortening
cycle and is the underlying mechanism of plyometric training.
Choose the method to fit the sport
The golden rule of any conditioning program
is specificity. This means that the movement you perform in training
should match, as closely as possible, the movements encountered during
competition. If you are rugby player practicing for the line-out or a
volleyball player interested in increasing vertical jump height, then drop
jumping or box jumping may be the right exercise. However if you are a
javelin thrower aiming for a more explosive launch, then upper body
plyometrics is far more appropriate.
Plyometric Exercises
The following are examples of lower body
and upper body plyometric exercises.
Lower Body
Drop Jumping: - This exercise
involves the athlete dropping (not jumping) to the ground from a raised
platform or box, and then immediately jumping up. The drop down gives the
pre-stretch to the leg muscles and the vigorous drive upwards the
secondary concentric contraction The exercise will be more effective the
shorter the time the feet are in contact with the ground. The loading in
this exercise is governed by the height of the drop which should be in the
region of 30 to 80 cm. Drop jumping is a relatively high impact form of
plyometric training and would normally be introduced after the athlete had
become accustomed to lower impact alternatives, such as two-footed jumping
on the spot.
Bounding and hurdling: If
forward motion is more the name of your game, try some bounding. This is a
form of plyometric training, where over sized strides are used in the
running action and extra time spent in the air. Two-legged bounds reduces
the impact to be endured, but to increase the intensity one legged
bounding, or hopping, can be used. Bounding upstairs is a useful way to
work on both the vertical and horizontal aspects of the running action.
Multiple jumps over a series of obstacles like hurdles is a valuable drill
for athletes training for sprinting or jumping events.
Examples of lower body plyometric exercises
with intensity level:
- Standing based jumps performed on the
spot (low intensity) - Tuck Jumps, Split Jumps
- Jumps from standing (low-medium
intensity) - Standing long jump, Standing hop, standing jump for height
- Multiple jumps from standing (medium
intensity) - bounds, bunny hops, double footed jumps over low hurdle,
double footed jumps up steps
- Multiple jumps with run in (High
intensity) - 11 stride run + 2 hops and a jump into sandpit, 2 stride
run in + bounds
- Depth jumping (high-very high intensity)
- jumps down and up off box (40 to 100cm), bounding up hill
- Eccentric drop and hold drills
(high-very high intensity) - hop and hold, bound/hop/bound/hop over 30
meters (athletes stops and holds on each landing before springing into
the next move), drop and hold from a height greater than one meter
Upper Body
A variety of drills can be used to make the
upper body more explosive:
Press ups & hand clap:
Press-ups with a hand clap in between is a particularly vigorous way to
condition the arms and chest. The pre-stretch takes place as the hands
arrive back on the ground and the chest sinks, and this is followed
quickly by the explosive upwards action. Once again, to get the best
training effect keep the time in contact with the ground to a minimum.
Medicine Ball: Another means
of increasing upper body strength popular with throwers is to lie on the
ground face up. A partner then drops a medicine ball down towards the
chest of the athlete, who catches the ball (pre-stretch) and immediately
throws it back. This is another high-intensity exercise and should only be
used after some basic conditioning.
Planning a Plyometric
Session
The choice of exercises within a session
and their order should be planned. A session could :
- begin with exercises that are fast,
explosive and designed for developing elastic strength (low hurdle
jumps; low drop jumps)
- work through exercises that develop
concentric strength (standing long jump; high hurdle jumps)
- finish with training for eccentric
strength (higher drop jumps).
An alternative session could be:
- begin with low hurdle jumps
- progress to bounding and hopping,
- continue with steps or box work
- finish with medicine ball work out for
abdominals and upper body.
Example plyometric sessions for the arms
and legs are detailed on the
Leg Plyometric page and the
Arm Plyometric
page.
Warm up
A thorough warm up is essential prior to
plyometric training. Attention should be given to jogging, stretching
(static and ballistic), striding and general mobility especially about the
joints involved in the planned plyometric session. A cool down should
follow each session.
How many ?
It is wise not to perform too many
repetitions in any one session and since it is a quality session, with the
emphasis on speed and power rather than endurance, split the work into
sets with ample recovery in between.
Where to do it and what to wear
For bounding exercises use surfaces such as
grass or resilient surfaces. Avoid cement floors because there is no
cushioning. Choose well-cushioned shoes that are stable and can absorb
some of the inevitable impact. All athletes should undergo general
orthopedic screening before engaging in plyometric training. Particular
attention should be given to structural or postural problems that are
likely to predispose the athlete to injury.
Conditioning for
plyometrics
Higher than normal forces are put on the
musculoskeletal system during plyometric exercises so it is important for
the athlete to have a good sound base of general strength and endurance.
Most experts state that a thorough grounding in weight-training is
essential before you start plyometrics. It has been suggested that an
athlete be able to squat twice his body weight before attempting depth
jumps. However, less intensive plyometric exercises can be incorporated
into general circuit and weight training during the early stages of
training so as to progressively condition the athlete. Simple plyometric
drills such as skipping hopping and bounding should be introduced first.
More demanding exercises such as flying start single-leg hops and depth
jumps should be limited to thoroughly conditioned athletes.
Young athletes
Some authors suggest that moderate jumps
can be included in the athletic training of very young children (Lohman,
1989). However, great care needs to be exerted when prescribing any
training procedures for preadolescent children. Because of the relatively
immature bone structure in preadolescent and adolescent children the very
great forces exerted during intensive depth jumps should be avoided
(Smith, 1975).
Summary
Plyometric type exercises have been used
successfully by many athletes as a method of training to enhance power. In
order to realize the potential benefits of plyometric training the
stretch-shortening cycle must be invoked. This requires careful attention
to the technique used during the drill or exercise. The rate of stretch
rather than the magnitude of stretch is of primary importance in
plyometric training. In addition, the coupling time or ground contact time
must be as short as possible. The challenge to you as coach or athlete is
to select or create an exercise that is specific to the event and involves
the correct muscular action. As long as you remember specificity and to
ensure there is a pre stretch first then the only limit is your
imagination.
Plyometric exercise and weight training can
be combined in complex training sessions to further develop explosive
power.
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