The development of strength and speed in sports is essential for enhancing athletic potential. Plyometric training is an effective way of increasing the power of athletes for whom sporting success relies on quick, explosive movements. Plyometric training involves exercises that elicits maximal force production in as short duration as possible. Plyometric actions utilize a muscular action known as a stretch-shortening cycle (SSC). The SSC describes the initiation of a rapid pre-stretch movement followed as quickly as possible by a forceful post-stretch contraction. The rapid pre-stretch movement serves to enhance the post-stretch contraction by taking advantage of stored energy in the non-contractile portions of the muscle, tendons and cell membranes. A pre-stretch that is increased either intentionally (through pre-exercise static holds) or due to the nature of the selected exercise (excessive load in the pre-stretch movement) will reduce the beneficial effect of the invoking of the SSC.

The importance of the SSC can be seen clearly in jump sports such as the long jump and in basketball, particularly in dunk competitions where vertical jump ability has a direct influence on success. In both sports, athletes use their running speed to increase the braking force required to stop forward movement prior to jumping upwards. This high braking load places extra eccentric force (i.e. the pre-stretch) through the muscles involved in vertical jumping. By the presence of this eccentric load, the athlete is able to transmit extra force into their jump bringing about a greater performance outcome.

Training intensity

Because of the intensity of plyometric training (i.e. high eccentric loads), it is essential that the frequency of the sessions is not excessive. This will vary depending on the athlete, sport and time of year. The recovery given during an individual session also needs to be sufficient to allow for complete recovery between sets of reps. Incomplete recovery leads to extra fatigue in completing the exercise, this results in an increase in ground contact time, consequently reducing the training effect of the exercise.

The SSC is split into three phases:

Eccentric

  • Stretch of the agonist muscle

Transition

  • Short pause between phases (<250 millisecond)

Concentric

  • Shortening of agonist muscles

Plyometric training typically involves jumping, hopping and bounding-type activities. Depending on the activity, it can be increased in difficulty by adding barriers of varying height to jump over, or boxes to jump on to, and to jump off.

Jumping activities that require an athlete to jump over an obstacle present an increased difficulty in coordination of the jumping movement. This increases the downward speed of the lower limbs prior to ground contact, and increases the muscular demand to complete the jump action.

The addition of a box to jump on to requires further skill and coordination to land, usually in a tucked position, on the box being jumped on to. This requires the athlete to transition rapidly from a jump action (hip, knee and ankle extension) to a tucked position (hip, knee and ankle flexion). Following this rapid transition the athlete must land in a controlled manner while in the tucked position.

Initiating a jump sequence from a box will significantly increase the eccentric control demand of the jump. Increasing the box height for the start of the jump will increase the velocity of the athlete at the point of contact, and will increase further the eccentric demand of the exercise. If the start height is excessively raised, then the transition from eccentric to concentric actions may be delayed excessively due to high braking forces being applied, and thereby reduce the effectiveness of the exercise.

Medicine balls can be added to throwing actions to add resistance. Like many training modalities, it is important to progressively increase the difficulty of plyometric exercises. This will facilitate development of the athlete while also helping to avoid injury that may be brought about by implementing training that is too demanding for the athlete. The progression of an exercise should occur as an athlete becomes more proficient in exercise technique and performance. The advancement of plyometric exercises should follow the progressions outlined below.

Lower Body Plyometric Progression

Jumps in place

  • Single efforts
  • Countermovement jumps, squat jump, tuck jump

Standing jumps

  • Distance jumps, lateral jumps
  • Addition of a barrier

Multiple jumps

  • Multiple standing jumps increases the intensity of the exercise
  • Forwards, backwards and lateral
  • Addition of a barrier

Bounds

  • Movements similar to sporting actions but with an exaggerated form

Box drills

  • Standing jumps onto a box
  • Height of the box will vary depending on the ability of the athlete

Depth Jumps

  • Stepping off a box, landing and immediately jumping maximally
  • Increasing the box height will increase the pre stretch force in the subsequent jump
  • Height of the box will vary depending on the ability of the athlete

Double support – Single support

  • Plyometric training should start with double leg support and progression to single leg support. This increases the difficulty of the exercise as single leg support increases the balance and force generation demands of the support leg.

Safety considerations in plyometric programming

Technique

  • Does the athlete have the correct technique in executing the exercise, in particular landing?

Strength

  • Has the athlete developed a sufficient strength base to avoid injury?
  • A common guideline is that an athlete should be comfortable in squatting in excess of 1.5 times their bodyweight if they are to undertake extensive high intensity plyometric training.

Speed

  • Can the athlete maintain sufficient speed of movement throughout the plyometric training session?

Balance

  • Does the athlete have sufficient balance ability to reduce injury risk in landing?

Physical state

  • Athletes with high body mass should avoid high volume, high intensity plyometric training.
  • Previous injury location and severity should be considered prior to training.

Landing surface

  • The landing surface should be stable, uniform and be able to yield slightly.

Footwear

  • Footwear should provide cushioning to avoid injury and provide good lateral stability.

Athlete Considerations

The ability level of the athlete and their experience in plyometric training will dictate the number of foot contacts per training session that are appropriate for their training level. Every effort should be made to ensure that this level not be exceeded during the session:

  • Beginner: 80-100
  • Intermediate: 100-120
  • Advanced: 120-140
    Based on this, a beginner basketball player may do a session of:
  • Jump with backboard touch 3 x 4
  • Lateral Jumps 3 x 6
  • Low hurdle hops 2 x 7
  • Jump onto box 3 x 5

Summary

Plyometric training is an excellent way to increase the power of athletes involved in speed-strength activities. Plyometric exercises take advantage of initiating the stretch shortening cycle resulting in an increase in the maximum rate of force development during training, which can consequently enhance maximum power during sports activity. There are a number of considerations in devising a plyometric training program, but prescribing exercise with these in mind will allow athletes to effectively increase their plyometric ability.