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The parameters used to determine if an athlete is strong enough

to begin a plyometric program may center more on testing of functional strength (including power) than on the traditional one- repetition maximum (1RM) squat that measures pure strength. One such test has been used by a number of practitioners in plyometric training programs. As a test of power more than strength, it may have more direct applicability. For the test, weight equal to 60 percent of the athlete’s body weight is placed on a squat bar, and the athlete is asked to perform five repetitions in five seconds, tested against a stopwatch. If the athlete cannot do so, the emphasis of the athlete’s training should be on a resistance training program, and the intensity of the plyometric training program should remain low to moderate. Poor strength in the lower extremities results in loss of stability

when landing, and high-impact forces are excessively absorbed by the soft tissues of the body. Early fatigue also becomes a problem for athletes without adequate leg strength. Together, these factors will result in the deterioration of performance during exercise and an increased chance for injury (as in any overuse situation).

Anaerobic, Sprint, and Interval Training Plyometrics trains two anaerobic energy systems—the creatine

phosphate system and the lactic acid system. The creatine phosphate system depends on energy stores that already exist in the muscles. Plyometric exercises that last a mere four to 15 seconds deplete the energy stores. In a program designed to train the creatine phosphate system, a considerable amount of rest or recovery should be allotted between exercises; the emphasis is on quality of work, not quantity. The lactic acid threshold is reached when the muscles’ energy stores have been exhausted by the creatine phosphate system. Exercise that proceeds past the point of using the energy stores will tax the lactic acid threshold. Exercise bouts at near-maximal effort that last around 30 to 90 seconds are appropriate for training that system. In general, jumps in place, standing jumps, and depth jumps are short-duration activities used to train the creatine phosphate system. Multiple jumps, box drills, and particularly bounding can qualify as exercises for training the lactic acid threshold. Training the creatine phosphate system is beneficial for athletes

involved in sports that require quick bursts of power with long recovery periods between performances, such as the long jump or triple jump. Training the lactic acid threshold is helpful for athletes in sports such as football or volleyball, where activity is fairly pro- longed and rest periods are more infrequent. Sprint and interval training are running programs that require

of plyometric exercises. In resistance training, the athlete works to develop the eccentric phase of muscle contraction by first lowering the body or weight and then overcoming the weight using a concen- tric contraction. Plyometric training can be successfully integrated with resistance training by immediately imposing a speed-strength task on muscles that have been subjected to pure strength move- ments such as those in weightlifting. Open-chain resistance training (using machines that isolate

a single joint) is useful for developing strength in specific muscle groups. However, athletes who use plyometrics also need to per- form closed-chain exercises that involve multijoint activities, such as free weight exercises using barbells, dumbbells, and medicine balls. These exercises, which are generally performed with the feet fixed to the ground as in squatting, are more functional for athletes, allowing them to assume positions specific to their sports when they exercise. Closed-chain exercises have proven themselves to have much higher carryover value than isolated-joint exercises in developing athletic ability. The more intense the plyometric exercises become, the more

crucial the need for strength. Some of the early European literature spoke of the need for athletes to be able to squat 2.5 times their body weight before undergoing a training program. There is no doubt that those authors had a high-intensity program in mind—with a goal that might be unreasonable for the average high school or age group athlete. However, a strength requirement is part and parcel of plyometric training at all levels.

the athlete to perform high-quality efforts in training for a certain amount of time (usually around 30 to 90 seconds) with prescribed recovery periods. This type of training is closely related to plyometric training of the lactic acid threshold, but sprints are used instead of multiple jumps, box drills, or bounding exercises.

Circuit Training One of the many benefits of plyometric training is that it can

be organized into circuits with other types of training. By moving from station to station, the athlete can do a variety of exercises that stress the vertical or linear components (or both) of various move- ment patterns. For coaches, circuit training also serves the purpose of group management very well. Entire teams can be involved in a circuit of plyometric exercises, thus ensuring some uniformity of exercise application and intensity levels. By using circuits, athletes can perform activities of even greater

duration than with anaerobic, sprint, or interval training. This may move the level of cardiovascular stress toward the point where im- provement in aerobic conditioning occurs, resulting in increased stamina. The cumulative effect of circuit training is considerable, so the recovery period should be at least two days.

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