The Joint Ventures' Blog

An Introduction To Plyometrics

Monday, May 21, 2018

Do you want to be more explosive so you can jump higher, run faster, be more agile, improve overall fitness, and help decrease your risk of injury? If you do, you may benefit from plyometric exercises. Plyometric training is a very specific mode of exercise, but it has a broad applicability to any activity that requires deceleration or acceleration of the body or the exertion of forces against the ground or an object. This is true with many athletic activities including running, jumping, throwing, and changing directions, but also with many daily activities.

Plyometric exercises use the inherent elasticity of muscles and the muscles’ stretch reflex to produce an explosive movement. This acts similarly to how a rubber band or spring responds when stretched. The stretch reflex is a link between the muscle and the spinal cord, which is one of the fastest reflexes in the body. Within the muscle is the "muscle spindle" which is a sensory organ that provides the body with information about the rate and intensity of stretch in a muscle. The mechanism of how plyometrics work is based on the stretch shortening cycle. Essentially, stored elastic energy from a rapid stretch in the muscle can be used to increase the force or power of subsequent movements.


There are three phases of the stretch shortening cycle: eccentric, amortization, and concentric. The eccentric phase involves pre-loading of the muscle with a rapid deceleration movement like during an "eccentric" or lengthening type of contraction of the muscles. Think of lowering into a partial squat before trying to jump. The muscles are contracting, but lengthening. This allows for energy to be stored within the muscle. The muscle spindle is stretched which sends a signal to the spinal cord followed by a return signal back to the muscle. The higher the rate of stretch, the better the ability to use the stretch reflex to generate more explosive movement. The amortization phase is the time between the eccentric contraction and the subsequent shortening or concentric contraction. It is important to keep this phase as short as possible to get the greatest response from plyometric movements. The concentric phase is the body’s response to the eccentric and amortization phase and the stored energy can be used to increase force production. Think of the explosive take off when jumping. If the body is not able to efficiently transition between the phases, the stored energy is lost as heat and the final product is a movement that is not as powerful.

Plyometric training has benefits beyond improved athletic performance. It can improve neuromuscular control and coordination. This is due to the synchronization of movements across multiple joints and muscles that occurs during plyometric training in order to accomplish a skill or task. These exercises also combine strength and speed to produce power. Being able to move explosively, or powerfully, not only relates to sport activities, but also day-to-day activities. Consider the need to suddenly increase your speed to cross the street as a car is approaching or if you suddenly lose your balance and need to move quickly to regain it. Plyometric training can help improve your ability to perform these tasks.


Plyometric exercises can range from low intensity to fairly high intensity in terms of demands and difficulty. The type of plyometric exercise depends upon the specific needs of the individual, as well as their ability and training level. Regardless, there is likely potential benefit to some type or intensity of plyometric training across all ages and fitness levels.

While plyometric exercises have many potential benefits, there is also an increased injury risk if not properly performed. These exercises generally require the body to manage higher levels of dynamic forces that can put increased stress on joints and muscles if there are errors in form or technique. It is important to have a good foundation of strength and basic movement skills so your body can manage these forces safely. Many injuries occur during the landing phase of jumping, so eccentric strengthening (or lengthening types of muscle contractions) are particularly important to help the body be prepared to absorb the forces upon landing. The concept of "triple flexion" refers to the eccentric activity of the muscles and joint of the ankle, knee, and hip to flex in unison with control during the landing process to absorb the forces of impact. Some exercises to address eccentric strengthening for the lower body are squats, deadlifts, and lunges.


It is also important to land with good posture and body alignment. This requires that your ankles, knees, hips, spine, and torso to all work together to disperse the forces on your body. Ideally, you want to land with your ankles, hips, and knees aligned - both from the front and side view. Your hips and shoulders should be square and facing forwards and your trunk upright. Some of the most common movement errors include landing too stiff with limited shock absorption; letting the knees become knock kneed; or letting the knees drive over the toes. This may be tough to picture in your head, but there is a video on or our blog site that can be referenced that provides a visualization on "triple flexion", as well as the desired alignment when landing and some examples of common landing errors.

There are certainly many additional aspects to consider when performing plyometric exercise training. These include proper warm up, specific exercise selection or intensity, volume, frequency, work to rest ratio, and recovery time. Covering all of these is beyond the intent of this blog post, but hopefully the information here is helpful and it gives you an introduction to, and basic understanding of, this mode of training in terms of what it is, its potential applications, and some form and technique considerations. If you have questions or would like more information, you can call our office at 617-536-1161 or email Dave Carleton at Dave.Carleton@JointVenturesPT.com.

 

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