Plyometric Training and Athletic Performance
When we think of a robust and complete training program, we think of a program that includes exercises that cover the entire force velocity curve. In other words, we want to include drills and exercises that are performed at low velocities with high loads, such as a heavy back squat, as well as ones that are performed at high velocities with low load, such as sprinting. Plyometric training, otherwise known as jump training, provides us with a great opportunity to link optimal strength training with optimal speed training. This is because plyometric training involves movements that are performed at moderate velocities that involve varying levels of forces, depending on the movement being performed.
Another benefit to plyometric training is kinetic linking. Kinetic linking occurs when the larger muscles that are more proximal in the body begin to fire to create energy. The proximal muscles then begin to transfer this energy to the more distal, smaller muscles as they begin to fire. The energy that is able to be saved from the proximal muscles and transferred distally results in maximal velocity at the distal segment. In plyometrics, the glutes represent the larger, proximal muscles. The glutes are able to transfer the energy they generate to the distal muscles in order to create powerful movement. Imagine trying to jump using only your calf muscles! Training plyometrics is a great way to teach athletes how to produce force both quickly and efficiently, which is essential for sport.
Athletes come to us because they want to get back to playing the sport they love and, in order to do so, they need to train movements that look similar to what they will see on the court or field. Plyometric training puts the athletes into some of the same shapes and positions that we see in sport and teaches them how to move efficiently while in those positions.
Plyometric Training and Injury Prevention
Not only do plyometrics help athletes to improve their performance in sport, but they have also been shown to reduce the risk of injury. One of the most debilitating lower body injuries field and court sport athletes suffer from is an ACL tear. A study conducted by Baldon and colleagues found that females who participated in plyometric training were able to improve physical qualities that have been identified as risk factors for ACL injury, such as eccentric hip strength, which is crucial for landing mechanics (2014). In a meta-analysis performed by Sadoghi and colleagues, it was discovered that athletes who participated in ACL prevention programs, which included plyometrics, reduced the risk of injury by as much as 85% in males and 52% in females (2012). It’s great having these studies to justify the implementation of plyometric training, but why is it that plyometric training may help to reduce the risk of injury?
Lower body, non-contact injuries frequently occur when an athlete is decelerating prior to changing directions. A big reason for this is that these movements require a high degree of eccentric strength to control the joint positions athletes must maintain to decelerate and change directions safely. When an athlete is unable to control these positions, we start to see movement faults, such as knee valgus, that place excessive stress on the ligaments and tendons. Loren Landow, Head Strength and Conditioning Coach for the Denver Broncos, has a wonderful analogy for this concept. Think of ligaments as guard rails on the side of a road. Our cars don’t rely on these guard rails to stay on the road, rather, they are a last resort when we lose control of our car. Plyometric training provides us with an opportunity to put athletes into positions similar to those they will be exposed to in their sport while teaching them how to absorb and produce force without putting unnecessary stress on their ligaments and tendons.
The Naming of Plyometric Exercises
It is important for us to understand how to name plyometrics in a consistent manner in order to limit confusion. If we are all able to speak a common language it becomes easier to discuss progressions and ensure the proper exercises are being implemented. When it comes to the naming of plyometric exercises, there are three components we must include. Those three components are movement, direction, and initiation.
Movement
· Jump – two foot take-off to two foot landing
· Bound – single foot take-off to opposite foot landing
· Hop – single foot take-off to same foot landing
As we progress from two foot to single foot plyometrics, we decrease the amount of stability the athlete has and there becomes a greater demand for eccentric strength. For this reason, we would begin with jumps during the return-to-play process and progress into single limb exercises.
Direction
· Vertical (Rotational)
· Lateral (Rotational)
· Linear
Vertical jumps are what we typically think of when we think of plyometric training. The force vectors that athletes produce during these types of jumps are very similar to those experienced during sprinting. Therefore, teaching athletes to be efficient at vertical jumping has the potential to make them more efficient when they reach top-end speed. One of the benefits of vertical jumps is that they limit the amount of rotary and shear forces that occur at the knee. For this reason, vertical jumps would be initiated first during return-to-play programming. A rotational element can be added as a progression when the athlete has demonstrated competency in the sagittal plane.
Lateral jumps occur in the frontal plane and provide us with an opportunity to begin teaching our athletes how to control rotary forces at the knee. Using a hurdle to add a more vertical component while performing these jumps can be a great way to limit these forces initially. As the athlete becomes more comfortable, we can remove the hurdle and even begin to add a rotary component as a progression when the athlete is ready. The force vectors present during lateral jumps are similar to those we see during change-of-direction movements.
Linear jumps begin to expose the athlete to more shear forces at the knee. Because anterior translation of the tibia is one of the mechanisms of ACL injury, linear jumping is typically the last plyometric progression that will be added into a return-to-play program. Just like lateral jumps, adding a hurdle can be a great way to limit these forces initially. The force vectors present during linear jumps are similar to those seen during acceleration and incorporating linear jumping into an athletic performance program can be a great way to improve starting strength.
I will be covering initiations in future blogs when I go into more detail on plyometric progressions during the return-to-play process (click here).
References:
· Baldon Rde M, Moreira Lobato DF, Yoshimatsu AP, dos Santos AF, Francisco AL, Pereira Santiago PR, Serrão FV. (2014). Effect of plyometric training on lower limb biomechanics in females. Clin J Sport Med, 24(1), 44-50.
· Sadoghi, Patrick MD; von Keudell, Arvind MD; Vavken, Partick MD, MSc. (2012). Effectiveness of anterior cruciate ligament injury prevention training programs. The Journal of Bone & Joint Surgery, 94(9), 769-776.