If you think this is just another article about plyometrics, think again. In fact, we might argue that much of what you have previously read about plyometrics is, at the very least, not about “true” plyometrics. For most CrossFitters, plyometric training is synonymous with jump training, the primary purpose of which is to improve box jumps.
Oh, far from it.
The Russian Influence
The technique of plyometrics was originally developed by Russian scientist Yuri Verkhoshansky as early as 1966. Verkhoshansky referred to plyometrics as a “shock method” of training. He primarily described how an improvement in performance can occur following a drop from height and subsequent immediate jump. The focus for Ver-khoshansky was the very short period between landing and takeoff, as short as 0.1 to 0.2 seconds.
However, what has developed since then is a more generalized version of plyometrics. This application of plyometrics specifically applies to improved performance in box jumps and is best termed “jump training.” Hops, bounds, split jumps, skips, squat jumps and depth jumps make up this broad-based approach to improving power. We often see this in use in American sports training today and frequently in CrossFit boxes. But there’s a big difference between what Verkhoshansky described and what we are now calling plyometrics. So let’s look at the science of the “plyo.”
Plyometrics is a system of training based on the effects of three different physiological factors and one neurophysiological factor, all of which result in what’s known as the three-phase stretch-shortening cycle (SSC).
Increased muscle force in a plyometric exercise stems from the following three physiological components. First, elastic energy in muscle tissue and tendons is stored during a rapid stretch and can be released if a contraction immediately follows that rapid stretch. Second, when a muscle is stretched, the microfilaments that cause muscle contraction may be at the best length to bind and produce force during a subsequent contraction. Third, there is resistance from muscle tissue itself (a kind of “rubbery” quality of muscle) during an unstimulated stretch; this “passive” resistance adds to the subsequent force generated.
Muscle spindles are specialized sensors located near where the muscle belly ties in to the tendon. Their job is to protect the muscle from damage caused by a stretch that is either too rapid or too lengthy (at the limit of the range of motion). Therefore, when a stretch occurs rapidly, the muscle spindle senses such a stretch as potentially dangerous and sends a signal to the central nervous system. The nervous system responds reflexively, immediately contracting the muscle in order to protect it. Plyometrics uses this reflex by adding the force of the spindle-initiated contraction to the muscle’s subsequent contraction during an explosive movement.
Now that you have a grasp of the forces involved in plyometrics, here’s how it all comes together in a real-life situation.
Three Phases of Plyometrics
In the first phase of the stretch-shortening cycle, the muscle is stretched when a force is exerted upon it. That force could occur upon landing or when the muscle encounters a resistance (such as a medicine ball). The muscle lengthens in this phase, called the eccentric phase, and the muscles involved in resisting that lengthening movement are being “pre-loaded.” In the simple case of running, when your foot strikes the ground, your gastrocnemius (calf muscle) lengthens under the load. Now, in the eccentric phase of a plyometric movement, your gastroc has stored energy by virtue of the factors cited above.
Let’s skip to the third phase. In this phase, known as the concentric phase, the stored energy is used to increase the force of the subsequent contraction. Because power is the product of force and velocity, the more force you provide to any contraction, the more power the muscles involved develop. In the case of running, more force is available upon a rapid stretch, and therefore the ensuing explosion coming off the toes on the next stride is greater.
But the phase we skipped is the critical one. The middle phase, which encompasses the time between the eccentric and concentric phases, is called the amortization phase. And the term “amortization” makes perfect sense. When something is amortized, its cost is distributed over a time frame. In the case of plyometrics, the stored energy is distributed as heat over the time frame of the amortization phase — the period after the muscle’s lengthening ends and before the shortening (concentric contraction) begins. The longer that phase, the more energy is distributed and lost, leaving less to be added to the subsequent contraction.
In other words, the shorter the amortization period, the better. In running, the longer your foot stays on the ground (“foot-strike time”), the less explosive you are.
Getting Back to “True Plyometrics”
So do you see the difference between what Verkhoshansky prescribed and what we normally do in the box? There are two main differences.
We do not properly apply or seem to appreciate Verkhoshansky’s “shock” method. Let’s face it, most CrossFitters know that plyometrics are to be done with some degree of speed, but that’s a far cry from the explosive shock that has been found to improve power.
Think of a typical plyometric movement in a box — a box jump. How often would you guess that the time period a typical athlete performing them has a foot-contact time less than 0.2 seconds? Not often. The degree of explosiveness that is needed for a true plyometric effect is simply not taught. But — and this is important — that doesn’t mean you can’t train that way.
The difference is a mental approach. Explosive and true plyometric training begins in your head. As an athlete, you determine, by your mental focus, how quickly you respond to any stimulus. When performing plyometrics, keep the idea of amortization foremost in your mind. Always concentrate your efforts on minimizing the time you engage the resistance. The effectiveness of plyometrics truly does start in your mind.
Second, as CrossFitters, we have perhaps failed to appreciate that true plyometrics can be performed with virtually any muscle group. The vast majority of CrossFitters only employ this technique when working on box jumps, and the exercises themselves typically include only boxes. Yet plyometrics is a muscle-oriented phenomenon, not a movement-oriented phenomenon. Therefore, to apply this principle in your training regimen, you should expand your plyometric training to include upper-body drills and not simply those that include foot strikes. With this in mind, here we orient you to some upper-body plyometric drills that can improve your overall body power. There are many, but these can get you started.
True plyometric exercises can be high intensity. Therefore, they are not to be performed for multiple sets or more than once per week until the athlete has become properly conditioned. While volume for lower-body plyometrics is based on foot contact, in upper-body plyometrics, we measure throws or catches. In general, when starting out, keep total plyometric volume to fewer than 100 per session.
In addition, we generally recommend avoiding high-intensity drops or throws for adolescents, senior athletes and those who have orthopedic injuries in the associated joints or muscles.
The 45-Degree Sit-Up
With a medicine ball weighing no more than 10 pounds (typical weights are 4 pounds for women and 6 for men), grab a partner and spot for sit-ups. Sit with your trunk at a 45-degree angle. Your partner should be in front of you with the medicine ball.
While you hold your hands outstretched, your partner throws you the medicine ball. Catch the ball with both hands, immediately propelling the ball back to your partner with your trunk remaining at 45 degrees. The key here is threefold. First, try to minimize any trunk extension upon receiving the ball. Second, your return throw should be as immediate and explosive as possible. Third, the force used to absorb the impact of the ball and return it to your partner should come from your abdominal muscles. You can increase the intensity of this exercise by simply using heavier medicine balls.
The Plyometric Push-Up
With a small medicine ball, like those weighing between 6 and 10 pounds, move into a push-up position. Remaining in that plank, place both hands on the ball directly under your upper chest. Of course, there is a degree of balance necessary here.
Now, as quickly as you can, remove your hands from the medicine ball and move them to the side of the ball in a push-up position. As you descend, allow your chest to barely touch the ball before you explode back up. At the top of the explosive push-up, move your hands back onto the ball. Make sure that your chest doesn’t rebound off the ball and that your hands hit the floor and explode into a push-up as quickly and forcefully as possible. In addition, keep your hands on the top of the ball, not the sides of it. You can add to the intensity of this exercise by increasing the size of the medicine ball.
With a staggered stance (one foot in front) and knees slightly bent, hold a medicine ball in both hands and stand 5 to 8 feet away from a wall. Pull the ball back behind your head and forcefully throw it forward as hard as possible against the wall. Catch the ball as it returns to you, and keep this action going. Remembering the amortization phase, minimize the time between pulling the ball back and initiating the throw. This drill can be performed with a partner instead of a wall. It also can be done with one arm, but we prefer the two-arm technique to minimize the potential of developing imbalances.
Stand with your feet shoulder-width apart and knees slightly bent. Pull a medicine ball back behind your head and forcefully throw it down toward the floor as hard as possible. Catch the ball on the bounce. The focus should be on minimizing the time the ball is in your hands. Think about cocking your arms and exploding downward as soon as you receive the ball. This exercise is done on occasion in CrossFit boxes but typically with “sausage”-type heavy tubes. Such weights do not allow as much of an eccentric phase because there is little pre-loading involved.
For this one, you need a medicine ball weighing no more than 10 pounds, a partner and a box (start with 20 inches) for him or her to stand on. Lie on your back on the floor with the top of your head against the base of the box. Your partner stands on the box with outstretched arms, holding the ball over your chest.
Extend your arms upward. On a signal, have your partner drop the ball directly down. Catch it using both hands, bending at the elbows to absorb the weight and then immediately propel the ball back to your partner. The intensity of this drill can be increased by either increasing the height of the box or by increasing the weight of the ball.
Stand with your feet slightly wider than hip-width apart. Lower your body into a semi-squat position (as in the bottom of a kettlebell swing). Have a partner throw you a medicine ball and catch it in the bottom position, letting your arms bring the medicine ball backward through your legs. Explode up, extending your entire body, and throw the medicine ball up and back over your body.
The goal is to throw the ball behind you as far as possible, generating as much power as you can from your hips and lower body. But again, the key is to explode upward as quickly as possible once you receive the ball.
Stand with your feet hip-width apart. Place one foot about 12 inches in front of the other. Hold a medicine ball with both hands and with your arms only slightly bent. Swing the ball over your hip on the side of your back foot. Then forcefully throw the ball underhand to a partner or toward a wall. Maintain tension in your trunk and abdominal muscles during the movement. Catch the ball from your partner or the wall and continue. As usual, concentrate on minimizing the time the ball is in your hands. Be sure to switch the order of your feet and train the other side, as well.