Introduction 

Plyometric training is an important element of the training programme of most top-level jumpers, including high jumpers. Although it has developed over more than half a century and been reported in the literature, its proper utilisation is still not fully understood by
many coaches. Some apply plyometrics incorrectly, which can reduce the positive training effects or even lead to injuries, while others avoid
the means, and thus compromise the potential performances of their athletes.

The aim of this article is to address this situation by providing a summary of the main aspects of plyometric training, drawn from the
current literature, as a general guide and as a starting point for further study and discussion.Special emphasis is given to the use of plyometrics in training for the high jump.

The main points to be covered are:
• The history of plyometric training,
• The scientific basis of plyometric training,
• Plyometric training compared to traditional
   resistance training and ballistic training,
• Integration of plyometric training in the
   athlete’s training programme,
• Practical aspects of plyometric training,
• Plyometrics and resistance training,
• Plyometrics and circuit training,
• Plyometric drills,
• Plyometrics and the high jump.

The History of Plyometric Training
Although western training scientists became aware of plyometrics in the mid-1970s,this form of training was developed in the Soviet
Union in the 1950s and early 1960s (DUKE,1990). The term was initially synonymous with triple jumpers and triple jump training (see, for
example, YOUNG & MARINO, 1985). To develop the type of loads that the plant leg had to withstand in the hop and step phases, athletes
trained by jumping down from one box onto the plant leg and instantly jumping up onto another box. The terms “stretch-shortening”
training, “depth jump” training, “reactive” training, “drop jump” training and “eccentricconcentric” training started appearing in the
literature more and more in the 1960s. A particularly important piece of literature at the time was a study by Verhoshanski (1967),
where he advocated depth-jump heights between 0.75 and 1.15m. According to REID
(1989), many coaches took this to mean athletes could develop the stretch reflex by jumping down from boxes higher and higher, land
on pre-stretched plant leg and bound back up onto another box. Such training was not substantiated
by scientific research and the injury score increased. However, over-zealous coaches often rationalised that athletes who could not
complete the drill were simply too weak.

Valeriy Borzov’s (URS) double victory in the sprints at the 1972 Olympic Games in Munich 1972 made everyone aware of how plyometrics
can be incorporated into a sprint training programme. Borzov made extensive use of various jumping exercises in his training but was by
no means the first sprinter to utilise plyometrictraining. Armin Hary (FRG), the 100m gold medallist in the 1960 Olympics, made use of various
jumping exercises throughout his training programme.Many sprinters have also participated in the long jump, the training for which serves a
similar purpose. A good example is Irena Szewinska (POL), the multiple Olympic medallist, who incorporated extensive jump training into
her programme (GAMBETTA, 1987).

However, plyometric training has by no means been the exclusive domain of the sprinters/ jumpers. Throwers, too, have used plyometrics,
both for the upper and lower body. Upper body plyometrics has mainly taken the form of medicine ball exercises using 3-6kg
balls. Janis Lusis (URS), former javelin world record holder and Olympic champion, made extensive use of jump training in the form of
hurdle jumps, hopping, and bounding to develop the explosive power in his legs. Plyometric type training has also been utilised
in the realm of middle distance and distance training. Hill bounding, advocated by Arthur Lydiard in the late 1950s, was designed to yield a
powerful stride but is nothing more than bounding with the added resistance of the hill. Pekka Vasala (FIN), the 1972 Olympic champion over
1500m, used a six-week period of a ‘bounding endurance phase’ in his training. This was performed up a 400m slope of 5-15° gradient.
All these examples show that plyometric training in itself is not new, but the proper application as a training method needs further clarification
and guidelines (GAMBETTA, 1987).

The Scientific Basis of PlyometricTraining

During plyometric, or stretch-shortening, exercises the muscle is rapidly stretched (eccentric contraction) and then shortened to
accelerate the body upward, as in a countermovement jump.
This stretch-shortening cycle has been demonstrated to enhance power performance to a greater extent than concentric training only (e.g. by performing squat jumps) (Bosco , Vii - tasalo , Komi & Luhtanen , 1982). The improved performance seen in the countermovement
jump is attributed to a greater amount of stored elastic energy acquired during the eccentric phase that is able to be recruited during
the upward movement of the jump (Bosco & Komi , 1979). In addition, the pre-stretch during
the countermovement results in a greater neural stimulation (Schmidtbleicher , Gollhofer
& Frick , 1988) as well as an increase in the joint moment (a turning effect of an eccentric force, also referred to as torque at the start of
the upward movement (Kraemer & Newton ,2000)). The greater joint moment results in a greater force exerted against the ground with a
subsequent increase in impulse (greater force applied over time) and acceleration of the body upward. BOBBERT et al. (1996) have suggested
that this latter mechanism may be the primary.

1. The primary training method has used traditional resistance training programmes with a relatively high intensity of training
(4-6 RM) performed at a relatively slow velocity of movement.

2. Plyometric training is another training method that is used to enhance power performance. Most plyometric exercises
require the athletes to rapidly accelerate and decelerate their body weight during a dynamic movement. The athletes’ body
weight is most often used as the overload, but the use of external objects such as medicine balls also provides a good training
stimulus for certain plyometric exercises.
3. The final method of training to enhance muscular power and explosive sports performance is a combination of traditional resistance
training and plyometric training.This form of resistance training is referred to as ballistic training. Ballistic movements
(see Figure 2) are forced movements initiated by muscle actions but continued by the momentum of the limbs (KENT, 2006).
Ballistic movements are performed at a much lower intensity of training (approximately 30% of 1 RM) using a much higher
velocity of movement (Wilson , Newton ,Murphy & Humphries , 1993).
The have three main phases:
1) an initial phase of concentric action that starts the movement,
2) a coasting phase that relies on the momentum generated in the initial phase, and
3) a deceleration phase accompanied by eccentric actions (KENT, 2006).