How do basketball players, sprinters, javelin throwers and triple jumpers – amongst many power sport athletes – develop so much speed, jump height, jump distance and throwing power?

The answer lies very much in what’s known as plyometric training. In this feature we look at some of the science behind plyometrics and provide a workout designed specifically for fitness purposes that you can use to power up your fitness.

Plyometric training was systematically developed in the former Eastern Bloc countries from the 1960’s onwards in particular – although its name derives from the adaptation of the methodology by the American coach Fred Wilt in the 70’s. Plyometric training and specifically the drop (or depth) jump (of which more later) development is largely attributed to the work of the former Soviet sports scientist Yuri Verkhoshansky. Verkhoshansky’s methodologies were based on considerable research and practical application.

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Due to the impact involved in plyometrics his methods became known as the ‘shock’ method. Verkhoshansky realised that muscle loadings and crucially outputs were significantly heightened by the use of the stretch/reflex capacity of muscles. This involves an eccentric to concentric pair of muscular actions. These occur rapidly when a jump is performed after a landing from another jump (and when running). The muscular actions can be compared to the action of a bow being pulled (the eccentric contraction) and the arrow’s release through the bow-string contraction at great velocity (the concentric action). It’s the priming eccentric (lengthening) muscular action that literally fires the concentric (shortening) one at a much higher level than otherwise would be possible.

Drop jumps Drop (or depth) jumps are a key part of plyometric training methods.

A drop jump requires an athlete to step, run or leap off a raised platform to land and immediately perform another jump or series of jumps. Jumps from the box and on landing can be made from either one of two feet, with landings alternating left and right (as would be the case with a series of bounds) or from the same side leg to the same side leg (as would be the case with a series of hops). Combinations of bounds and hops can also be performed.

The emphasis of the post landing jumps can be placed on achieving greater vertical or horizontal distance (or combination of). Drop jumps can be performed with added loads such as carrying dumbbells or whilst wearing a weighted vest. The latter method – of which more later – obviously increases the resistance of the exercise. Drop jumps can also be loaded in order to enhance the concentric contraction through the use of elastic bands – again of which more later. Perhaps the key resistance drop jump variable is drop-height.

This variable can have a very significant outcome on the transference of the conditioning activity into actual sports performance. The higher the height the greater the force absorbed through the legs on landing (the greater the shock). At first glance this may appear to be very useful in terms of developing athletic strength. It’s possible for the muscles of the legs and hips to absorb five+ times the athlete’s body weight on landing. These are levels of resistance that would not be possible using other resistance methods i.e. weight training.

However, although this is the case the subsequent concentric contraction’s speed is reduced if the drop-height is too great. This is seen to be negative in terms of directly improving dynamic sports performance and is attributable to the fact that too much time will be spent on the ground absorbing the impact, through the eccentric contraction before energy  is returned through the concentric contraction into the jump. Amoritization is the term used in sports conditioning circles to refer to the “link” in between the stretch/reflex (eccentric-concentric) plyometric action. It refers to the way muscles absorb the impact from the shock of landing from a drop jump (or other plyometric activity) and their transition into the concentric concentration.

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How to get the most from plyometric training

Speed of landing must be focussed on if maximum gains are to ensue. When jumping the athlete must ‘fire’ their muscles to jump as high or as long as possible and with as much speed as possible, failure to do so will not recruit the largest and most powerful motor units (collections of fast twitch muscle fibre and the nerves that fire them). Verkhoshansky experimented and discovered that the optimum height for developing ‘explosive strength and reactive ability’ was about 75cm. This research was based on evaluation of different drop-heights from 0.15m to 1.55m.

The jump performed involved a double foot jump off the platform, followed by a double-footed landing and double-footed jump for height. Top-level, track and field sprinters, jumpers and throwers were the research subjects, which adds credibility to the findings. It’s crucial that athletes and coaches take this fully on board when constructing a plyometric programme. Speed of landing reaction must be emphasised if the athlete is to gain the most from the activity in terms of improved speed and power and the height of the drop must be carefully controlled accordingly. But what about using drop jumps to develop strength? Verkhoshansky then discovered that if this was the desired outcome then the optimum height to drop from would be 1.50m (again using a double footed off, land and double-footed jump for height method).

So by varying the height from which the athlete performs a drop jump (given Verkhoshansky’s parametres) the coach can manipulate the training response. This allows for drop jump training to be periodised, in much the same way as barbell loadings are manipulated in the weights room to achieve different training outcomes. Australian researchers looked at drop jump training on vertical jumping and quadriceps’ strength. Thirty-five males participated in the study and two training groups were established, together with a control group.

Both workout groups performed 72-90 drop jumps a week for 6 weeks. One group emphasised maximum rebound height and the other height and speed of reaction. Various tests were used pre-and post-testing to measure performance – these included, vertical jumps from standing and running and leg strength as measured under concentric and stretch/reflex (plyometric) conditions. The  ‘reactive’ group improved their reactivity by 20% but not vertical jump performance, whilst surprisingly the ‘height’ group did not improve on any measures significantly.

This lead the researchers to conclude that, training for height through slower reaction drop jumps was, “….not specific enough to stimulate gains in strength qualities of the leg extensor or jumping muscles.” Given the findings of Verkhoshansky previously presented it’s possible that had the research used different drop jump methodologies (more specifically those prescribed by Verkhoshansky) and that training had been periodised then a greater positive training response would have been elicited – one that improved both jump height and reactivity.

 

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