 With all of the talk concerning vertical jump and plyometrics, it's no wonder so many athletes are tapping into this area of training. Can plyometrics and jump training help you? Are jump training and plyometrics dangerous? What can I expect to gain from these training methods--1 inch increase in my vertical leap? Or can I expect to gain 10 or 12 inches? These are some of the most common questions that are asked about plyometrics and jump training. In the following article, I will answer these questions to the best of my knowledge based on current studies and research.
Let's first talk about vertical jump. Being able to jump high involves many factors. Some of these factors you can control. When we talk about born leapers, we're talking about the percentage of fast-twitch muscle fibers in the important areas (legs) being higher than average. In most people, the difference in the percentage between slow-twitch (great for endurance athletes) and fast-twitch is relatively small. Usually the person's percentages are close to 50%-50% or 60%-40%. How much fast-twitch do you have? Well, there are tests that can be done to approximate this percentage, however, they are very costly. Chances are you already know if you have a huge difference in these percentages. If you were a really fast sprinter in junior high or you ran a 5 minute mile in junior high, you can make an educated guess.
It has been discovered that this fast-twitch/slow-twitch separation is not so simple. Research has uncovered the fact that along with these great fast-twitch and slow-twitch fibers, there are also fibers that have properties  of both of the fibers. Now for the great news. These fibers are influenced in a major way by specific training. Therefore, doing training that focuses on quick movements (jumping, sprinting, etc..) enables these muscles to develop the properties of fast-twitch muscle fibers. In order to train these muscles, we must pay attention to the concept of "specificity." Specificity involves the reaction of muscles or muscle groups to training. If you train a muscle group by moving it at a high speed, then eventually that muscle group will be stronger--but only at that speed. In fact, in recent studies, the concept of specificity has been shown to be even more prevalent in all types of training. If a muscle group is trained at a certain angle, then it will only show strength improvements at that angle. The concept of specificity should be kept in mind in all levels and all types of training.
So, what does this have to do with jump training? Well, many different types of training are used and considered effective, even though some are simply not useful and even dangerous. When a technique produces results, it doesn't necessarily mean that it was that specific technique that produced those results. Sometimes, the positive training effects that occurred, came about in spite of that training technique (because of some other factor). Keep in mind that training should make sense (because of the concept of specificity), so if a technique seems "off the wall" and a friend says it worked for her, don't jump (ha ha) to conclusions.
Let's look at a few concepts we need to keep in mind when jump training:
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