From the Trainer
By Ryan Unverzagt
Plyometrics Part Deau!!
This article is the second of a two-part series about Plyometrics. In last month’s issue, I explained what plyometrics are and some important things to consider before trying this type of exercise such as age, strength, body weight, previous injuries, and training experience. Exercise safety is a top priority of mine because if you get hurt, that means you can not exercise! Where is the benefit in that?
Before jumping right into the plyometric exercises, I would like to explain how it works. The body is an extremely complex machine, especially during exercise. There are thousands of chemical reactions going on that allow our bodies to even move. These reactions work in harmony with our nervous system, which essentially dictates how the body responds to stimuli. The nervous system is integrated within our muscles to help detect body position changes. This phenomenon is called proprioception. These proprioceptors are sensitive to tension and stretch of the muscles. Plyometrics work
because of the body’s stretch reflex.
The stretch reflex is an involuntary response (contraction) to any stretching of the muscle. When the muscle is stretched out quickly, this reflex will kick in to tell the muscle to shorten in order to protect it from ultimately tearing. This leads me to mention the stretch-shortening cycle. The basis of this cycle is that a stretched muscle will store potential energy which contributes to a more powerful muscle contraction when combined with voluntary contraction (in this case, jumping).
Now that you know the physiology behind plyometrics, let’s talk about the actual exercises and program design basics. The most common plyometric exercise is jumping rope. You probably have at least tried this activity without even knowing that you were doing plyometrics! Jumping rope takes some skill and concentration as do all jumping exercises, so practice makes perfect.
If you are just starting a plyometric program, you should have a soft surface to jump and land onto (such as a wood or carpeted floor, or grass; not concrete) and a comfortable pair of sneakers. The number of jumps or foot contacts depends mostly on training experience. The beginner should aim for about 50 jumps total during a workout. This number should be slowly increased by about 10-15 jumps per week. The total number can reach as high as 200 in one workout! The intensity of each jump should be max effort and the goal is not to jump until fatigue because this will lead to injury. Rest is another important thing to remember. Never perform plyometrics two days in a row. You should aim for two workouts per week with at least 48 hours of rest in between.
The most basic plyometric exercise is called the counter-movement jump. This is done by standing with your feet about shoulder-width apart. Start by bending your hips and knees to a half squat position (45 degree knee angle) while extending your arms behind you, then immediately jump up quickly by extending your hips, knees, and ankles forcefully while also swinging your arms forward and up. Arm action will help your muscles take advantage of the stretch-shortening cycle that I explained earlier. You want to achieve as much “air time” as possible before landing softly by re-bending your hips, knees, and ankles. To start, you should rest a few seconds between jumps then progress to multiple jumps without rest.
Another plyometric exercise is called the box jump. This is done in the same manner as the counter-movement jump, except you will land on top of a plyometric “box” or an elevated surface such as a park bench or steps if you are outside. You should start out at a comfortable height (maybe 6-8 inches, about the same height as a step) and progress to higher surfaces such as a park bench. It’s a good idea to step down after landing a jump initially before jumping back down to start the next jump.
The final plyometric exercise I will mention is the lateral cone (or line) hop. Again, this is performed in the same way as the counter-movement jump with powerful arm action, except that you will jump laterally over a cone or line. Land softly before jumping back toward the same spot in which you started. This exercise requires a little more balance than the first two, so start out slowly before trying faster, multiple jumps.
I strongly urge you to consider all the safety precautions that I wrote about in the last issue and also check with your doctor before giving plyometrics a try.