Plyometrics is the method of training which enhances explosive physical reaction through powerful muscular contractions resulting from rapid eccentric contractions. These muscular contractions are achieved mainly through a variety of jumping, bounding and hopping exercises. This training relies on basic equipment such as steps, hurdles, medicine balls and jump ropes.
Whatever plyometric exercise you utilize, the underlying mechanism becomes the stretch shortening cycle: in each exercise, the muscle is rapidly stretched (or "loaded") before it is contracted. So plyometrics essentially builds elastic strength: a concentric contraction (muscle shortening) needs to occur immediately following an eccentric contraction (muscle lengthening) in order to achieve the desired dramatic increase in force. When muscle stretches in this manner, its elastic components store some of the energy and make it available during a rapid subsequent contraction.
Personal trainers often favor plyometrics to boost strength and speed, along with the balance, coordination and stability of their client's athletic performance. Notes Arizona based trainer Mark Francis: “I like to use the physio ball instead of regular machines and freeweight benches to incorporate stability in the trunk." Plyometrics requires having a good existing strength base and should not be done more than twice a week for a period of six weeks or less. With this in mind, some specific suggestions he outlines for the tennis player, for instance, run as follows:
- The X-box jump. - difficult but effective. Similar to regular side box jumps, this exercise also requires an individual to jump off the front and back of the box in addition to the sides.
- Do not attempt the X-box jump until totally comfortable with regular side box jumps.
- The square cone drill. The athlete navigates four cones placed approximately 10 yards apart in a square with exercises such as side shuffles, backpedal and high knee runs, continuing for a set number of reps or a time period. Speed and agility should be the emphasis of this exercise.
Even if you have only recently begun a regular exercise program, you can include some plyometric movements. “A tennis player, for example, could add side box jumps to his leg workout, which should emphasize lateral motion and stabilization,” Mark points out. This basically involves an athlete jumping laterally on and then off a 10 to 12 inch high box. Again, the emphasis should be on control and decreased foot-to-ground contact time. Athletes from within the same sport can use the same plyometric movements no matter what their level in that sport: “What would change dramatically would be the intensity based on the individual's existing physical ability,” he observes. “
Generall “do’s and don’ts” for anyone getting into plyometrics:
- Any session should take place a surface such as the grass in the outdoors or rubberized flooring indoors. Avoid concrete and wood.
- Before any session, warm up--a five minute walk, calisthenics or low intensity hopping and jumping to elevate your core body temperature.
- Perform the more complex plyometrics first since these require more energy, muscle synergy and concentration. “I always advise beginners to take their time and concentrate on form, not intensity,” Mark concludes: “It’s almost like learning to walk again, it can be very awkward doing some of these exercises, but the body soon adapts."
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FURTHER PLYOMETRIC READING:
Explosive Power: Plyometrics for Bodybuilders, Martial Artists and Other Athletes, by Ed Derse (Health for Life, 1994)
Power Training for Sports: Plyometrics for Maximum Power Development, by Tudor O. Bompa (Mosaic Press, 1997)
Jumping into Plyometrics, by Donald A. Chu (Human Kinetics, 1998)
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