Antagonistically Facilitated Shock Training

By Cal Dietz with Kevin Kocos

Antagonistically facilitated shock (AFS) training describes a novel manner in which to perform shock training or, as it’s more commonly known, plyometrics. AFS is an advanced method of training that requires an athlete to have previous experience in plyometrics.

Plyometric training is a term that was popularized when the training system made its way to western countries. Originally known as “shock training,” plyometrics were developed in the 1960s by Soviet sports scientists such as Yuri Verkhoshansky, often referred to as the “father of plyometrics.” For the purposes of this article, I will refer to the system as 'shock training.'

Shock training takes advantage of the body’s potentially powerful stretch shortening cycle (SSC). The SSC is optimally employed when the muscles and tendons, arranged in series, are subjected to a powerful stretching or eccentric contraction. The result is an incredible amount of potential energy. As has often been noted, a stronger and faster eccentric contraction will yield a more powerful concentric action. According to the late Dr. Verkhoshansky, true shock training is performed when the amortization phase (point at which the load makes contact during shock training before it is reversed in the opposite direction) and take off are performed in 0.15 seconds or less.

AFS training differs from conventional shock training because the powerful eccentric action placed on the muscle tendon series is initiated by a strong contraction of the antagonist musculature. For this to happen, there must be a simultaneous relaxation of the agonist muscle group while the antagonists are being recruited. The relaxation between opposing muscles becomes very significant, as L. Matveyev posited that athletes who increased this “relaxation” ability ultimately would distinguish themselves from their lesser qualified peers. This was most dramatically evident with the highest level athletes, Masters of Sport, who showed a relaxation time nearly 200 percent faster than novice level athletes.

This sounds a bit confusing, so let's look at one common example—the counter movement jump. An athlete normally squats down rapidly, thereby improving the ability of his body’s elastic qualities. This, however, wouldn't be true shock training, as the ground contact lasts much longer, ultimately limiting the potential for force output.

Regular Box Jump


Now, compare that with an AFS counter movement jump. The athlete pulls his hips down with the large hip flexors and hamstrings. The result seems to be that the feet and legs lift off the floor. In reality, the athlete is pulling into a position with such force that this “drop” occurs as a byproduct of the movement. The anterior knee extensors (the agonists of the jump) will relax while the downward descent is facilitated by the antagonists (hip flexors and hamstrings) pulling the athlete down. This brings the athlete into a very advantageous power position (a knee joint angle of approximately 45–60 degrees). As soon as the athlete strikes the ground, there must be an all out effort by the athlete to reverse the action as fast and explosively as possible, achieving maximum height in the vertical portion of the jump.

Squat Drop Jump

When performed correctly, AFS training creates a higher amount of eccentric force, thus creating a greater amount of stretch within the muscle tendon series which in turn will enhance force output on the concentric action.

To create optimal conditions for power output, loads should be approximately 20–30 percent of the athlete’s one rep maximum. This ensures that the athlete will be able to withstand the impact of weight and maintain a high velocity. This is absolutely crucial as in the development of power. Too often, people focus on the force component of the power equation and neglect the velocity aspect. For almost every sport I work with as a strength and conditioning coach, the goal for your athletes should be to produce a high amount of force at a high velocity.

Here's an example of AFS upper body training. The athlete pulls his hands away from the bar (a spotter has a hold of the bar the entire time). As the load reaches his chest, the athlete abruptly stops the load and simultaneously reverses the direction of the bar, throwing it as high as he possibly can through the air. By throwing the bar as high and fast as he can without any deceleration at the top, power production is maximized.

Bench Press Reactive Toss

AFS training, though similar in appearance to conventional jump training, is very taxing on the central nervous system. It’s imperative that only advanced athletes with experience performing plyometrics do them. A lower level athlete, when performing high intensity shock methods, might become overtrained with only twenty contacts, thus diminishing his training capabilities for too long a period of time. A higher level athlete who has been trained to handle high amounts of stress might need 30–50 contacts in order to create a training stress sufficient to elicit adaptation. The key with this style of training is quality, so keep at least 6–10 seconds in between efforts to ensure highly productive shock contractions and maintain joint stiffness. If you notice that the athlete spends too long on the ground or tends to dampen or deform in joint angle upon landing, he probably isn't ready yet for AFS and should return to general strength training with an emphasis on eccentric and isometric qualities.

Plan this method accordingly. Understand that in-season may be too stressful for some athletes whereas others can get by with less intensive means. Be aware of the inherent risks, program wisely, and you’ll find out for yourself how this method of training can create an explosive, reactive athlete!


  • Siff MC (2003) Supertraining. Denver, CO: Supertraining Institute.
  • Yessis M (2008) Secrets of Russian Sports Fitness and Training. Michigan: Ultimate Athlete Concepts.
  • Zatsiorsky V (2006) Science and Practice of Strength Training. Second edition. Human Kinetics.

This article is a small excerpt from Cal Dietz's soon to be released book, Triphasic Training: A Systematic Approach to Elite Speed and Explosive Strength Performance.

Kevin Kocos has directed the strength and conditioning program for men’s basketball at Minnesota since 2010. He also assists with the training of men’s and women’s hockey, men’s track and field, men’s swimming, and men’s and women’s golf programs. In Kevin’s time at the University of Minnesota, he’s been a part of five Big Ten Championship teams as well as two WCHA Championship teams. His athletes at Minnesota have earned over fifty All-American honors and have collectively won 29 individual Big Ten Championships as well as three world championships.