─Three Phases─
In every resistance training exercise that you perform, there are three phases to the lift. The first phase, generally what folks call the “hard part”, is the concentric phase. This is when the muscle is actually working, or shortening. The opposite of this phase, when the muscle is being stretched out or lengthening, is called the eccentric phase. To portray a better picture of these two phases, imagine yourself performing a squat. As you come down from a standing position, your glutes – the main movers of the squat – are being stretched out. The lower you go, the more your glutes are lengthened. Now, as you start to come back up, these glutes transitioning from a super-stretched position to a shorter and shorter phase. As you come up, the glutes should be contracting to help bring your hips into extension (so that you are standing straight up). On the way down, your glutes were going through an eccentric phase, and as you came up, your glutes were going through the concentric phase of the squat. For many people, these are the only two phases that matter in any kind of lift, mainly because the third phase is not commonly known or discussed. The third phase of any resistance movement is known as the amortization phase. This is the point of the lift in which absolutely nothing is happening. Go back to imagining the squat I just mentioned. You go through the eccentric phase as you come down, and before you start to stand back up, your body goes through a shift or change in direction. For a split second, no work is being done at all because you started traveling the opposite way. The amortization phase is that change in direction, or the phase when your body is in neutral.

─ Amortization Phase ─
This third phase that is rarely mentioned is actually the most important of the three phases when we considering the proper technique of a plyometric movement. When we go for a jump, it is absolutely imperative that our amortization phase be as short as possible. Think about a basketball player jumping up to receive a rebound. As the ball is in the air, you do not notice the player come down into a squat and hang out until it is time to jump. Instead, you see the player quickly bend his hips and knees and explode up as fast as possible to get the ball. This is because he is allowing his body to take advantage of its elastic stretch-reflex properties. Basically, the longer you hang out in the amortization phase, the more energy is lost. As a result, you lose force production, and when talking about plyometric training, you jump lower than your maximum potential.

Now that we understand the important of keeping the amortization phase as short as possible, we can start looking into the proper mechanics of the take-off and landing. For these next two sections, I will use the box jump example.

─ Take-Off ─
The most important aspect to remember of the take-off phase is that your body will only jump as high as your mind will let it. There have been countless times when a client of mine sees a stack of boxes that he or she feels is too high and immediately starts saying “I can’t jump that high”. Guess what? After they say that, I remove a step to make the box lower, because they have already lost the battle by saying those words. With plyometric training, the less you think, the better you perform. With the box jump, remember that your upper and lower body should be working together, not against each other. The human body works most effectively when it is working as a system.
For example, with the box jump, the goal is to jump as high as you can onto the box. For your upper body to be working as a team with your lower body, your arms should swing upward as well. I cannot tell you how many times I have seen someone jump on a box only to see that as they jumped up, their arms flew down by their sides. Not only does this increase the chance of you scraping your shin on the box, it does so by adding the weight of your arms down by your side as you attempt to jump. Again, to jump higher, understand your body works as a unit. The anterior deltoids will help propel you upward as you jump, which will result in far less potential injuries.
─ Landing ─
My biggest pet peeve regarding plyometrics is hearing a THUD every time someone lands on top of the box. If I have my back turned to you and I can still hear every time you land on top of the box, you are not performing the jump the right way. As mentioned in the Plyometric Training article, this type of training utilizes the central nervous system to communicate with the muscles effectively. If your landing on top of the box is hard, this is a sign that your neuromuscular communication is not working up to par. One thing that usually gets this message into a client’s head is telling them to “think like a ninja”. The softer you land, the less impact on your joints. The less impact on your joints, the longer you can perform jumps and lifts without any injuries or setbacks.
My second biggest pet peeve when thinking about plyometrics is seeing people stack boxes extremely high, only to jump onto the box with their knees up their ears. This is not a true plyometric jump. Again, plyometrics take into account how explosively you are coming up. By landing with your knees all the way up by your face in excessive hip flexion, you have not proved how high you can jump but rather how much flexibility you have in your hips. As a general rule, try to land on top of the box in the same position that you took off from. Generally you will drop down about a quarter of the way. Aim to land on top of that box in a quarter squat as well. This will be an effective experiment of how high you can truly jump.

Plyometric Training is a very technique-based training. Many times, I have had folks ask me what they can do to start jumping higher. When they ask me this, I turn back at them and ask them to show me how they jump. Usually, I notice an error in their technique and advise them to correct that error, then to worry about the height of the box. Commonly, within one week, they conquer that box they were attempting to jump onto. Technique. Technique. Technique.

Throughout the Plyometric Articles, I have discussed jumping using only the legs. However, that is only half of the equation of plyometric training. Lower body plyometrics are very common, but what if someone comes to me saying they want to increase their upper body explosiveness? Upper body plyometrics can be worked into a program effectively, and nothing changes as far as technique goes. Make the amortization phase as short as possible, and explode into the concentric phase as fast as possible. Use your body as a system and do not let it counter itself. And please land softly to avoid breaking your wrists!