Plyometrics: Kangaroo vs Gorilla

“What are you talking about, a gorilla would totally beat up a kangaroo?” Not quite what we are talking about. Let’s compare and contrast a kangaroo and gorilla and see what different qualities they possess and how they can help our athletic development. 

When you think about a kangaroo, what do you think of? Probably that they are springy, hop quickly, and spend little time on the ground when they are moving. 

When you think about a gorilla, what do you think of? Probably that they are muscular, can produce high amounts of force, and do not bounce around everywhere they go. 

A kangaroo is not (relatively) strong and a gorilla is not (relatively) fast. 

Remembering back to our previous blog about plyometrics, a plyometric is defined as a quick stretch (eccentric) followed immediately by a rapid contraction (concentric). The rate at which the muscle-tendon unit stretches and contracts matters. If it is not fast enough, we do not get to utilize the middle phase, the amortization phase, and subsequently the stretch-shortening cycle (SSC) of the tendon; it is no longer considered a plyometric movement. This matters because of the viscoelastic nature of the tendon. The faster we transition from the eccentric phase into the concentric phase, the more elastic potential energy gets converted into kinetic energy, and therefore more power into our plyometric movement. If we spend a long amount of time on the ground, our tendons do not help us and we are solely utilizing the force that our muscles produce.

If all of the above is satisfied, the movement should feel like a reflexive action, as opposed to a conscious “push” by the athlete. Good cues for this may be to “tap the ground,” to “bounce,” to “land stiff,” and to “not sink.” Poor cues may be to “load and explode,” “sit into it,” or “push through the floor.” 

Thinking about the kangaroo and gorilla, there is a continuum of plyometrics from fast to slow. A fast plyometric is generally considered under 250ms and a slow plyometric can be up to around 700ms of ground contact time (GCT). If an athlete spends any longer on the ground, the movement is mostly muscular, as opposed to tendinous, and you lose the plyometric nature of the movement. These are better known as short-coupled and long-coupled plyometrics, respectively. 

There is also another category of plyometrics that relate back to the kangaroo and gorilla and that is whether the movement is extensive or intensive. An extensive movement is a movement that you can perform for an extended period of time. An intensive movement is done with high intensity and is unable to be performed for long periods of time. Think about a kangaroo hopping around all day versus a gorilla winding up to take his first swing at 100 men trying to attack him (the gorilla would win, by the way). 

It is important to understand these different types of plyometrics in order to appropriately rehab an athlete back to their sport. All of these categories matter, they just matter more for some sports than others. A therapist also has to be able to test each of these categories to assess whether the athlete needs more of one versus the other.

So remember, in order to be training plyometrics, you need to satisfy all of these criteria: 

• The movement has to have an eccentric phase and concentric phase

• The ground contact time must be short - less than 700ms but ideally less than 250ms

  • This allows the tendon to be involved (SSC) 

• The movement should be reflexive. The athlete should focus on producing as much force as possible muscularly, but if there is no reflexive nature to the movement, the tendon contribution will be minimal 

As an athlete, are you more like a kangaroo or a gorilla? Does that matter for your sport? Has an injury caused this change on the plyometric continuum? If so, schedule with a provider that can assess these qualities and help guide your rehab and training.