Plyometrics

Put the combination of speed and strength as power. Speed and strength are integral components of fitness found in varying degrees in virtually all athletic movements. For many years, coaches and athletes have sought to improve power 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 training method for power or explosiveness has been termed plyometrics. Plyometrics is based on the understanding that a concentric muscular contraction is much stronger if it immediately follows an eccentric contraction of the same muscle.

Plyometric Phases

A plyometric exercise comprises three phases:

The eccentric or landing phase involves the agonist muscle group's pre-loading (energy is stored).
The amortization or transition phase is the time between the concentric and eccentric phases. This time needs to be as short as possible. Otherwise, the energy stored during the eccentric phase dissipates, reducing the plyometric effect.
The concentric phase, or take-off phase, uses the stored energy to increase the force of the movement.

Muscle Mechanism

The maximum force that a muscle can develop is attained during a rapid eccentric contraction. When a concentric contraction occurs (muscle shortens) immediately following an eccentric contraction (muscle lengthening), the force generated can be dramatically increased. However, muscles seldom perform one type of contraction in isolation during athletic movements.

If a muscle is stretched, much of the energy required to stretch it is lost as heat, but its elastic components can store some energy. This stored energy is available to the muscle only during a subsequent contraction. It is essential to realise that this energy boost is lost if the eccentric contraction is not followed immediately by a concentric contraction. The muscle must contract within the shortest time possible to express this more significant force. This 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 a rugby player, practising 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, upper body plyometrics is far more appropriate if you are a javelin thrower aiming for a more explosive launch.

The Klatt Tests

Before starting a plyometrics programme, it is worth conducting the Klatt tests with the athlete. The tests include basic plyometric movements. If they are achieved, it can be assumed the athlete is ready for a plyometrics programme.

Plyometric Pyramid

The following British Athletics diagram shows a jumps progression for track and field athletes.

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 immediately jumping up. The drop-down gives the pre-stretch to the leg muscles (eccentric phase), and the vigorous drive upwards is the second concentric contraction phase. The exercise will be more productive the shorter the time the feet are in contact with the ground. The loading in this exercise is governed by the drop height, which should be 30 to 110 cm (Bompa et al. 2005)^[2]. Drop jumping is a relatively high-impact form of plyometric training. It would typically be introduced after the athlete had become accustomed to lower impact alternatives, such as two-footed jumping on the spot.

The two critical factors in drop jumping are minimal contact time with the ground and the height achieved in the drive upwards. Schmidtbleicher (1992)[3] says that a ground contact time of <0.25 seconds indicates a fast stretch-shortening cycle (SSC) and to adjust the drop height to achieve this contact time. Observe the athlete's feet if contact mats are not available to measure the contact time. On landing, the athlete should stay on the balls of the feet (mid-foot). The drop height must be reduced if the heels come into contact with the ground. Start at a drop height of 30cm and increment the drop height in 15cm steps.

The Reactive Strength Index (RSI) was devised to measure the interaction of the contact time and height jumped to monitor explosive power development. RSI is calculated by dividing the height jumped (metres) by the contact time (seconds).

Comyns (2012)^[4] recommends the key coaching points for the drop jump are:

Minimise ground contact time - imagine the ground is a hot surface
Keep your legs stiff on landing
Minimise the flexion at the knee and hip on landing
Land on the mid-foot under your hips
Maximise the height you jump - jump as high as possible

Focus on: JUMP FAST, JUMP HIGH

Bounding and hurdling

If a forward motion is more the name of your game, try some bounding. It is a form of plyometric training, where giant strides are used in the running action, and extra time is spent in the air. Two-legged bounds reduce the impact to be endured, but to increase the intensity of one-legged bounding, or hopping, can be used. Bounding upstairs is a valuable way to work on the running action's vertical and horizontal aspects. Multiple jumps over obstacles like hurdles are useful drills 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 a low hurdle, double footed jumps up steps
Multiple jumps with a run in (High-intensity) - 11 stride run + 2 hops and a jump into a sandpit, 2 strides run in + bounds
Depth jumping (high-very high-intensity) - jumps down and up off box (40 to 100cm), bounding uphill
Eccentric drop and hold drills (high-very high-intensity) - hop and hold, bound/hop/bound/hop over 30 metres (athletes stop and hold on each landing before springing into the next move), drop and hold from a height greater than one metre

Examples of lower body plyometric exercises are detailed on the Leg Plyometric page.

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 are a particularly vigorous way to condition the arms and chest. The pre-stretch occurs as the hands arrive back on the ground and the chest sinks, 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 way to increase upper body strength, popular with throwers, is to lie face up on the ground. A partner then drops a medicine ball down towards the athlete's chest, who catches the ball (eccentric phase) and immediately throws it back (concentric phase).

It is another high-intensity exercise and should only be used after necessary conditioning.

Examples of upper body plyometric exercises are detailed on the Arm Plyometric page.

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 a medicine ball workout for abdominals and upper body

Some examples and explanations of plyometric exercises for the arms and legs are detailed on the Leg Plyometric and Arm Plyometric pages.

Plyometric drills and their intensity

Type of exercise	Examples	Intensity
Standing based jumps performed on the spot	Tuck Jumps Split Jumps Squat Jumps	Low
Forward jumps from standing	Bounds and hops over 10 to 20 metres	Low to Medium
Multiple double legs hop from standing	5 bounds 6 bunny hops Double-footed jumps over hurdles Double-footed jumps up steps	Medium
Multiple single legs jump from standing start	Single leg hops up stadium steps	High
Drop Jumps	2 x 6 jumps for height or distance	High
Speed bounds	4 x 20 metres	High
Multiple jumps with run-up	3 x 2 hops and jump into a sandpit with a 5-stride approach 2 x 10 bounds with a 5-stride approach	Very High

Warm-Up

A thorough warm-up is essential before plyometric training. Attention should be given to jogging, stretching (dynamic), striding and general mobility, especially to 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. With the emphasis on speed rather than endurance, it is a quality session, split the work into sets with ample recovery in between. An experienced athlete conducting lower body plyometrics may conduct up to 150-200 contacts in a session. In essence, athletes new to plyometric work should start with moderate to medium intensity exercise with around 40 contacts per session, e.g. 2 sets of 6 bunny hops is 12 contacts. A similar approach should be taken with upper-body plyometrics.

The focus must always be on quality and not quantity.

Recovery

Allow at least one minute of rest between each exercise repetition to allow the neuromuscular system to recover. Allow three days between plyometrics sessions when planning.

Where to do it and what to wear

Bounding exercises use surfaces such as grass or resilient surfaces. Avoid cement floors because there is no cushioning. Choose well-cushioned, stable shoes that can absorb some of the inevitable impacts. All athletes should undergo general orthopaedic screening before engaging in plyometric training. 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 the athlete needs to have a good sound base of general strength and endurance. Most experts state that a thorough grounding in weight training is essential before starting plyometrics. It has been suggested that an athlete be able to squat twice their body weight before attempting depth jumps. However, less intensive plyometric exercises can be incorporated into a general circuit and weight training during the early stages of training to condition the athlete progressively. 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.

Conditioning programs to develop leg strength are detailed on the Lower Leg Conditioning page and the Leg Conditioning page.

Young athletes

Some authors suggest that moderate jumps (low intensity) can be included in the athletic training of very young children (Lohman, 1989)^[1]. 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 high forces used during intensive depth jumps (high-intensity) should be avoided (Smith, 1975).

Summary

Plyometric-type exercises have been used successfully by many athletes as a method of training to enhance power. The stretch rate rather than the magnitude is of primary importance in plyometric training. To realize the potential benefits of plyometric training, the stretch-shortening cycle (SSC) must be invoked. It requires careful attention to the technique used during the drill or exercise. Also, the coupling or ground contact time must be as short as possible. As a coach or athlete, the challenge is selecting or creating an exercise specific to the event involving the correct muscular action. If you remember specificity and ensure there is a pre-stretch first, then your imagination is the only limit.

Plyometric exercise and weight training can be combined in complex training sessions to develop explosive power.

References

LOHMAN, T.G. (1989): Assessment of body composition in children. Pediatr. Exerc. Sci. 1, p. 19−30.
BOMPA, T. et al. (2005) Periodisation Training for Sports. 2nd ed. USA: Human Kinetics
SCHMIDTBLEICHER, D. (1992) Training for power event. In: Komi PV (ed) Strength and power in sport. Blackwell Scientific, London, pp 381-395
COMYNS, T. (2012) Exploding into action, Athletics Weekly, December 6 2012, p. 58-59

Page Reference

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MACKENZIE, B. (1997) Plyometrics [WWW] Available from: https://www.brianmac.co.uk/plymo.htm [Accessed