Plyometrics – Why?

Plyometric training is very misunderstood old beast. Whilst many seek to reap the proposed benefits of plyo’s, few truly understand the mechanics that underpin them. Appreciating the kinetic and kinematic demands of different movements is integral if you’re to maximise the potential transfer to sporting performance.

Plyometrics – What?

Knowing what defines activities as ‘plyometric’ is probably a good place to start. I’ve written on this previously, so I’ll direct you there for more detail. The CliffNotes version? It needs to exploit the stretch-shortening cycle (SSC) to augment the concentric output.

Plyometric vs Stiffness Training

Semantically, ‘plyometric training’ and ‘stiffness training’ should not be used as interchangeable terms. Activities may be plyometric and not develop stiffness, for example, a countermovement jump.

Conversely, activities may develop stiffness but not be truly plyometric. This is true when the goal of the activity is to minimise ground contact time (thus minimising deformation) such as during pogo hops.

Start with Why

It is integral that any exercise within a programme is implemented with a clear rationale. This process starts with having a thorough understanding of the sport. What characterises the movement(s) you’re trying to improve?

  • Are they sprinting, jumping, hopping or something else entirely?
  • Is it single and explosive or repeated and submaximal?
  • Are they performing on one leg or two?
  • Is the movement in the sagittal, frontal or transverse plane?

The Burning Question

Once you know the movement profile, there’s one key consideration you can’t overlook.

  • How long have they got to produce force?

The time in which you’re in contact with the ground is perhaps the most important factor that will influence how you train.

Fast or Slow SSC

Schmidtbleicher (1992) defined ‘fast’ and ‘slow’ SSCs based upon a threshold of 250 ms. Whilst SSC duration is better considered upon a continuum than on a single threshold value, it does help highlight the independence of these qualities. For example, Flanagan (2007) reported that explained variance between the countermovement and drop jump was only 35%.

What Adaptation Do You Want?

Once you understand what you need, you can plan the adaptations you intend to induce.

  • Are you looking to develop stiffness and minimise ground contact times?
  • Are you purely seeking to maximise the impulse that can be transferred?

The intended adaptations will drive the activities you choose and how they should be performed.

When is a Drop Jump not a Drop Jump?

Think plyometric training and you probably think drop jumps. However, it’s not the exercise that’s plyometric, it’s how the exercise is performed. Bobbert et al. (1987) characterised two basic drop jump techniques: the ‘bounce’ and ‘countermovement’ styles. Whilst the general movement and overall jump height achieved may be the same, the way these two contrasting styles are performed confer distant mechanical demands.

Summary

Before incorporating plyometric training it’s crucial to consider the following:

  1. Understand the mechanisms which underpin them
  2. Understand what demands are imposed on the athlete (needs analysis)
  3. Understand what you need to develop for the individual athlete (testing)
  4. Define what adaptations you’re trying to induce
  5. Choose and perform exercises to match the intended adaptation

 

References
Bobbert MF, Huijing PA, Van Ingen Schenau GJ. Drop jumping. I. The influence of jumping technique on the biomechanics of jumping. Medicine & Science in Sport & Exercise. 1987: 19: 332-338.
Flanagan EP. An examination of the slow and fast stretch shortening cycle in cross country runners and skiers. Proceedings of the XXV International Symposium of Biomechanics in Sports. 2007: 51-54.
Schmidtbleicher D. Training for power events. In: Komi PV, ed. Strength and Power in Sport. Oxford: Blackwell Scientific Publications, 1992:381-395.

 

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