A good trainer or coach will have a range of techniques designed to get the best out of his trainee or athlete. For sports people in particular, it is important to be able to develop speed and force – without necessarily needing to increase strength.

Plyometrics, sometimes referred to as explosive jump training, or high velocity ballistic training, is the exercise technique designed with this in mind. This article looks at the science and techniques of plyometrics.

The ability of a muscle or muscle group to generate force varies throughout its full range of movement. Where that maximum force is required will vary depending on the sport. Plyometric training will develop the ability of the athlete to produce the maximum force where it is required for his sport.

Warning: The examples given below are by way of explanation, not genuine exercises. Don’t try them!

knowledgeable instruction on correct technique is important before attempting plyometrics.

Visualise a gym bench press using a barbell. Now visualise a bench press which requires the barbell to be thrown high in the air! The same muscles are involved, but the power requirements are different. Who needs that technique? Well, a footballer who takes a powerful throw-in, or a rugby player who has to forcefully throw an opponent out of his way as he heads for a try.

Visualise a barbell squat. Now visualise a barbell squat which requires you to jump in the air at the end. A volleyball player, high jumper or footballer needs a powerful jumping technique.

Finally, visualise a standing triceps extension using a dumbbell. Now visualise throwing the dumbbell across the gym at the end of the move. A javelin thrower or shot putter needs this power at the end of the triceps extension. A strength trainer has a different power requirement than that of a javelin thrower.

Once again, it is stressed that the examples given above are descriptive only, and should not be attempted!

Plyometric training involves repeated practising of the moves not only to toughen the muscle tissue, but also to train the nerve cells to perform a specific movement. This will eventually alter the firing and timing of the motor units involved in the muscle action, to give maximum power where the athlete requires it. Movement is a combination of muscle and nerve action which needs to be learned and trained.

Muscular power is defined as how long it takes for strength to convert to power. Someone who can squat with heavy weights will not necessarily make a good high jumper. The jumper has been specifically trained using plyometric techniques, to get more explosive power from each muscle contraction.

Plyometric exercise overloads the muscle, producing a rapid and forcible stretch (eccentric phase) immediately before the shortening (concentric) phase of the action. This produces a more powerful movement due to both the nervous action and the greater potential energy of the stretched muscle.

Safety considerations:

It is estimated that a drop jump generates a skeletal load up to ten times that generated by body mass alone – plyometrics are not for everyone, and certainly not for overweight or deconditioned people.

As a guide, someone who cannot manage five barbell squats at 60% of their bodyweight should not be doing plyometric training, and athletes who weigh over 100kg should select low intensity exercises, as should athletes not yet in their teens. The latter could be very important where younger children often participate in a number of sports, with a number of different coaches who do not communicate at all with each other.

The exercises should be carried out on a surface with a degree of spring – a sprung gym floor, rubberised multisports surface or grass is ideal, certainly not concrete. Good quality, supportive footwear is also essential.

There is plenty of material offering the benefits of plyometric training, but there are significant risks if the above safety points are not considered.

Plyometric exercises are demanding on the muscles and joints, and should only be performed by individuals who are already well conditioned in terms of flexibility, strength and proprioceptive reflex. As with any form of exercise, a good warm up, some gentle flexibility stretches and knowledgeable instruction on correct technique is important before attempting plyometrics.

The exercises themselves can sound like child’s play: standing jumps, multiple jump, alternate leg jumps, jumps from height, single leg jumps, box jumps / hops, hurdle hops, skipping, tyres / ladders and a multitude of variations. For advanced trainees only, a weighted squat jump, but only jumping a few centimetres off the floor.

For the athlete who needs to develop throwing power, a medicine ball is often used. The ball is thrown at them (or dropped on them!), and they immediately throw it back.

A typical plyometrics session could be approaching 100 impacts.

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