In an earlier article, I discussed Verkohshansky’s depth jumps and how his research was the starting point for modern-day plyometics. In this article I will describe the mechanisms of plyometrics. I'll also tell you how to do a few relatively simple kettlebell swing exercises to elicit a plyometric response, and explain the benefits of these exercises.



Stretch Shortening Cycle

When you ask someone to jump, you will usually see the person bend down at the hips and then accelerate upward. There are two mechanisms why we take this little down-dip. They are known as the stretch reflex and the mechanical storage of kinetic energy. Both of these mechanisms improve our explosiveness and provide reason why plyometrics work so well.


Stretch Reflex of Plyometrics


When we land from jumping, we are activating the stretch reflex. The stretch reflex is the body’s involuntary response to muscles being stretched. It is elicited in the doctor’s office when the doctor taps on the tendon below the knee. The knee kicks outward involuntarily because of a feedback loop in the spinal cord. When we land from a jump, we activate this reflex (the dip down also activates this response but to a lesser extent).


Mechanical Storage of Kinetic Energy


We also store the kinetic energy when we land from a jump. Anthony Turner and Ian Jeffries described different theories for how we store this energy. There is an active debate about how much is stored in tendons and how much is stored in muscle fibers, and it’s actually an interesting debate. A simple way to think about it is that we are loading a spring when we land from a jump. If we jump again right away, then we can utilize the energy from this spring.


Benefits of Plyometrics

The more we do plyometrics, the more our body responds and builds explosive power. This explosive power can help our absolute strength (e.g., deadlift), speed strength (e.g., clean), and pure speed (e.g., sprinting). Basically, we are learning to load our muscles with potential energy to release it again later.



Depth jumps can be difficult for many athletes because they are complicated movements and increase the risk of injury. Teaching a good squat can be difficult, but a depth jump adds complication as the person has to land in a perfect squat position, absorb shock, and take off quickly. It is recommended that the person can handle squatting at least 1.5 times his or her bodyweight (with good form) before attempting depth jumps.


A Less Risky Method

A less risky method would be to do Russian kettlebell swings with an emphasis on the downward (eccentric) portion. Instead of the weight of our body being absorbed as it is in depth jumps, we absorb the shock of the kettlebell when it switches directions. The more we force the kettlebell to come down, the greater the plyometric effect. In the lab, experienced kettlebell instructors like Pavel Tsatsouline and Brett Jones can make a 24kg kettlebell come back down with the force equivalent to three times their bodyweight.


An analogy often used to compare kettlebell swings and the deadlift is that swings are like a bullet being fired and a deadlift is like a rocket. When a bullet is fired, it receives all of its force from the initial explosion of gunpowder. A rocket receives continual propulsion from the engine. The main point of doing kettlebell swings is to train our explosive strength when we reverse force. The more force we have to reverse, the more strength we will gain.


To continue our analogy, doing overspeed eccentric kettlebell swings is building a hair trigger that we can fire very quickly with a lot of force. There are multiple stories of advanced powerlifters adding strength to their deadlifts by doing these types of kettlebell swings. Kettlebell swing overspeed eccentrics can be accomplished in three ways, which are all demonstrated in the video below:


  1. Accentuate the Eccentric – Generally, we let the kettlebell float into position and let gravity take it back down into our next swing. However, we can actively accelerate it downward by throwing it down and between our legs. 
  2. Partner Assisted Downward Throw – Have a person stand on the side and push down on the kettlebell when it reaches the top.
  3. Band Assisted Eccentric – Wrap a band around the kettlebell and stand on the band. Once the kettlebell hits the top of the swing, the band will accelerate it back down.



Here is some additional reading to familiarize yourself with the concept of overspeed eccentric training:




1.Cook, Christian J., C. Martyn Beaven, and Liam P. Kilduff. 2013. “Three Weeks of Eccentric Training Combined With Overspeed Exercises Enhances Power and Running Speed Performance Gains in Trained Athletes:” Journal of Strength and Conditioning Research 27 (5): 1280–86. doi:10.1519/JSC.0b013e3182679278.

2. Isner-Horobeti, Marie-Eve, Stéphane Pascal Dufour, Philippe Vautravers, Bernard Geny, Emmanuel Coudeyre, and Ruddy Richard. “Eccentric Exercise Training: Modalities, Applications and Perspectives.Sports Medicine (Auckland, N.Z.) 43, no. 6 (June 2013): 483–512. doi:10.1007/s40279-013-0052-y.

3. Turner, Anthony N, and Ian Jeffreys. “The Stretch-Shortening Cycle: Proposed Mechanisms and Methods for Enhancement: Strength and Conditioning Journal 32, no. 4 (August 2010): 87–99. doi:10.1519/SSC.0b013e3181e928f9.


Photo 1 courtesy of CrossFit Empirical.

Photo 2 courtesy of Shutterstock.