Plyometric Training : Replicating the Biomechanical Demands

Plyometric training has shown to be an effective power-based training method within sports performance, with previous research investigations demonstrating significant improvements in vertical jump performance (Markovic et al, 2007), ballistic push-off performance (Potdevin et al, 2011), sprint performance (Rimmer et al, 2000) and change of direction performance when applied within a frontal plane of motion (e.g. lateral bounds) (Miller et al, 2006).          

Plyometric training derives from a form of jump-based training firstly formulated by Yuri Verkhoshanky as a means of increasing rate of force development in Soviet track and field athletes and was one of many pioneering training methods derived from Soviet research on athletic development. Verkhoshansky applied a particular form of plyometric training known as accentuated eccentric training, whereby the eccentric portion of a landing is ‘accentuated’ by having the athlete perform a prior landing from a greater height, therefore increasing the eccentric forces upon landing. The greater eccentric forces resulted in a greater magnitude of kinetic energy, therefore resulting in a greater transfer of energy during the ground contact phase and a greater rebound or take-off action.

Plyometric Mechanical Models 

Plyometric exercises can be performed in a variety of ways depending upon the desired training outcome and demands of the sport action being replicated. In particular, it is imperative that the kinetic demands of the sport are matched and not just the kinematics. This translates to the replication of ground contact times (kinematics), RFD magnitudes and power output (kinetics) seen within sports performance, which vary depending the sporting action. The three plyometric mechanical models that can be applied to replicate these varying sport demands are as follows:

Concentric Dominant

By definition a plyometric exercise involves an amortisation phase or ‘prior landing accentuated eccentric’ as previously described. However, many sporting actions require an explosive type ballistic push off without any form of prior accentuated eccentric contraction or landing phase such as a block start in sprint swimming or sprint events, scrumming within Rugby, takedowns within mixed martial arts, etc. Therefore, if an athletes chosen sport requires such explosive ballistic push-off demands, then the implementation of concentric dominant plyometrics is necessary. Furthermore, when taking an athlete through long term plyometric progressions, it is essential that an athlete can firstly land correctly and perform concentric dominant type jumps (in conjunction with strength training) before progressing onto more advance plyometric training forms.    

Tendon Compliance

Tendon compliance based plyometrics involve a prior accentuated eccentric (prior landing) and therefore an amortisation phase. However, upon landing the athlete flexes at the ankles, knees and hips to the degree that they feel necessary before exploding into the next secondary jump. This manifests itself as a ‘absorbing the depth’ type movement pattern when landing before jumping the next jumping action. This allows the musculotendinous unit to lengthen whilst storing kinetic energy, before recoiling and transferring this stored energy into the next planned immediate jump. This ability to store and utilise kinetic energy is vital to many sporting actions and is a key stage within plyometric progressions.       

Tendon Stiffness

Tendon stiffness is the ability to produce rapid RFD within the shortest ground contact time possible, and therefore involves little flexion at the ankles, knees and hips upon landing. As little change in joint angle occurs during the execution of tendon stiffness based plyometrics, most of the mechanical work occurs within the tendon rather than the muscle itself. For example, upon landing from a drop jump plyometric, the muscles that plantar flex the ankle perform a quasi-eccentric-isometric contraction. This means the muscles are being held isometrically within the same position before being eccentrically lengthened under load and can therefore operate at the high-force section of the force-velocity curve whilst the tendon undergoes a rapid stretch-recoil action. The greater the tendon stiffness, the greater the RFD and energy economy of the movement, as less actual muscle work occurs compared to a concentric dominant or tendon compliance-based jump.  

The mechanical differences highlighted between each of the following plyometric models demonstrates the need for coaches to fully understand the biomechanical demands of an athletes chosen sport before implementing plyometric training. Practitioners should also be aware of an athletes current plyometric training status, and where within the plyometric progressive model an athlete is at, before programming plyometric-based training within sports performance.