This is an excerpt from High-Powered Plyometrics-2nd Edition by James C. Radcliffe & Robert C. Farentinos.
Is serious plyometric training a good option? Before getting too far in planning the specifics of a program, the prudent approach is to look honestly and carefully at factors that could affect safe participation in such intense training.
Prior to starting a progressive 12-week program, participants must have a proper foundation. This includes adequate strength, good fundamental exercise techniques, and an understanding of the risks of injury and how to recuperate from workouts.
Trainers must know participants' ages; genetics factors; and levels of experience, health, fitness, and strength. Those planning their own programs should treat assessment at least as seriously because they are their own trainers! They should look for any limitations that might inhibit progressive development in explosive power training.
Chronological age is an important consideration. Bosco and Komi (1981) demonstrated that the maturity of both the nervous system and the skeletal system affect people's tolerance of plyometric training. Youngsters who have not yet reached puberty, for example, should not participate in plyometrics, especially at intense levels. The continual growth of the skeletal system, cartilage at the epiphyseal plates, joint surfaces, and apophyseal insertions make the extreme forces of some plyometric exercises inappropriate.
The inability of young people to tolerate the high loads of the stretch - shortening cycle can cause confusion because they are exposed to forces during play and sports that may equal or exceed the forces experienced in plyometric training with a proper progressive system. The fact is that kids are vulnerable to excessively hard play, yet not as vulnerable as they are to consistent repetitions of excessive overloads.
We contend that 12- to 14-year-old participants can use plyometric training to prepare for future strength training. This has been corroborated by researchers including Valik (1966) and McFarlane (1982). However, we suggest using moderate jump training with youths. Early progressions of low impact and small dosages, as the guidelines and the continuum in later chapters suggest, are best. Adolescents do not appear to experience any significant response to explosive strength training until after the onset of puberty; therefore, training programs should be prescribed cautiously. Planned progressions are particularly appropriate so that young people receive the many other benefits (e.g., good mechanics, coordination, structural integrity) until maturity and mastery develop.
As age increases, nervous system capability, muscle and joint pliability, and energy production decrease, which makes plyometric training less attractive for older athletes. On the other hand, evidence suggests that decreased explosiveness is only partly due to the natural aging process. Increases in endurance training, a lack of such training, and lifestyle also influence how much explosive power a person maintains at older ages. Continued use of stretch - shortening cycle training in proper progressions and using moderate intensities can be effective for aging athletes, as evidenced by the growing numbers of masters athletes in explosive sporting events (e.g., track and field, weightlifting). As addressed in further chapters, anyone's capabilities can be evaluated and their training adjusted based on maturity.
Physical Capabilities and Health Limitations
Having a good level of overall fitness is helpful in all areas of exercise, and training for explosive power is no different. A doctor's physical exam is helpful. Before undertaking such training, people should have good body weight control and body composition, enough cardiorespiratory fitness to exercise continuously for several minutes or more, the strength to handle their own body weight in movements in all planes, and the mobility to handle movement positions in several ranges of motion.
Several physical areas should be assessed not only when planning training but also to determine limitations. Flexibility is one, especially in the ankle joints and calf muscles, to ensure proper foot mechanics and proper hip set and segmental cushioning. Evaluators should examine posture, noticing especially the use of torso mechanics; pelvic tilt; and the positioning of the cervical, thoracic, and lumbar spine. They should check out balance, torso tilt, and each appendage's joint alignment, as well as the stability of the foot in contact with the ground, stance firmness, joint tension, and coordinated control.
Past injuries may limit a person's ability to perform plyometric exercises. Joint stability and balance should be examined to note any past knee, ankle, or shoulder injuries. As mentioned in chapters 5 through 7, progressive exercises are useful in rehabilitation from injuries. Limitations on explosive training may arise from back or spine problems. Excessive trauma to these or any other areas that cause improper landing capabilities need to be addressed and planning adjusted.
Table 4.1 lists the capabilities and health conditions that indicate a readiness or lack of readiness to participate in plyometric training.
Athletes respond differently to training regimens. Coaches need to be sensitive to these individual differences, and athletes themselves must have some self-awareness. For example, differences between males and females show up both in training and performance. In addition, genetic makeup dictates, to a large extent, a person's ability to improve. Factors such as limb length and muscle fiber type distribution have a direct effect on performance. Both athletes and coaches need to be aware of limitations that can arise in training and development. Although these limitations may affect the rate of an athlete's progress, they should not influence the basic design of the training regimen.
The training age, or level of experience, a participant brings to working with stretch - shortening cycles can be more important than chronological age. Some athletes who have had several years of experience as competitors, for example, have never trained for competition. Some maturing athletes have been extremely skilled in their athletic endeavors and possess enormous talent, yet bring only an infantile level of training as a base. These athletes can be at high risk if they use poor technique and undertake exercise quantities that their body structures are not ready for. Coaches must determine athletes' technical and developmental levels by using quality training assessments (posture, balance, flexibility, and stability) as described in chapters 1 through 3 regarding core strength, postural control, and pretension.
Strength Training Base
Because a strength base is advantageous in plyometric training, a general strength training program should complement, not retard, the development of explosive power. However, establishing a strength base before plyometric training does not have to be a huge endeavor. An often-prescribed recommendation is the once-used Russian suggestion of being able to perform a maximal squat of one and a half to two times one's body weight before attempting depth jumps and similar shock training. This criterion is still useful as a safety protocol for the extreme end of the stress continuum. However, it is not necessary for the other stretch - shortening cycle exercises used in the beginning and intermediate portions of the continuum. In our more recent research (Radcliffe and Osternig 1995), we found that some correlation exists between squat performance and depth jump capabilities. However, the significance was so low that any predictions about how well the amount of weight squatted determined jump stress capabilities are negligible.
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