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Plyometrics, also known as "jump training" or "plyos", are exercises in which muscles exert maximum force in short intervals of time, with the goal of increasing power (speed-strength). This training focuses on learning to move from a muscle extension to a contraction in a rapid or "explosive" manner, such as in specialized repeated jumping. Plyometrics are primarily used by athletes, especially martial artists, sprinters and high jumpers, to improve performance, and are used in the fitness field to a much lesser degree. ==Introduction== The term "plyometrics" was coined by Fred Wilt after watching Soviet athletes prepare for their events in track and field; he felt this was a key to their success.〔Wilt, Fred & Yessis, Michael. ''Soviet Theory, Technique and Training for Running and Hurdling.'' Vol 1. Championship Books, 1984.〕 It is a poor term to describe what happens, but it has since been accepted and is now well established. When Wilt learned of the work being done by Michael Yessis on Soviet (Russia) training methods, they quickly collaborated to help disseminate information on plyometrics. Since its introduction in the early 1980s, two forms of plyometrics have evolved. In the original version of plyometrics, created by Russian scientist Yuri Verkhoshansky, it was defined as the shock method. In this, the athlete would drop down from a height and experience a "shock" upon landing. This in turn would bring about a forced eccentric contraction which was then immediately switched to a concentric contraction as the athlete jumped upward. The landing and takeoff are executed in an extremely short period of time, in the range of 0.1- 0.2 seconds. The shock method is the most effective method used by athletes to improve their speed, quickness, and power after development of a strong strength base.〔 Rather than using the term plyometrics to indicate exercises utilizing the shock method, it may be preferable to use the term explosive or true plyometrics which can be considered the same as the plyometrics originally created by Verkhoshansky.〔 The shock method that he created was the result of studying the actions that occur in running and jumping. He found that the landings and takeoffs in these two skills involved high ground reaction forces that were executed in an extremely quick and explosive manner. For example, time of execution of the landing and takeoff in jumping was close to 0.20 seconds and in sprinting it was approximately 0.10 seconds.〔 Since one of the main objectives of the Soviet research was to develop practical methods of training to improve athletic performance, Verkhoshansky tackled the task of how these forces in explosive execution could be duplicated in an exercise. By doing exercises such as the depth jump, that he created, the athlete would enhance his ability in the takeoff and his resultant performance in the running or jumping event.〔 He experimented with many different exercises, but the depth jump appeared to be the best for duplicating the forces in the landing and takeoff. The second version of plyometrics, seen to a very great extent in the United States, relates to doing any form of jump regardless of execution time. Such jumps cannot be considered truly plyometric (as described by Verkhoshansky) since the intensity of execution is much lower and the time required for transitioning from the eccentric to the concentric contraction is much greater. The term plyometrics became very popular with the publication of many books on the subject matter. It now appears impossible to go back to its original meaning and method of execution. As a result, it is important to distinguish which type of "plyometric" exercise is used in order to determine its effectiveness and potential to receive the stated benefits. Though the name plyometrics is given to all jumps, not all jumps are plyometric. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Plyometrics」の詳細全文を読む スポンサード リンク
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