There is no better way to describe the power of incorporating plyometeric exercises into a conditioning program for developing speed, power and agility. Plyometrics, or "plyos" are a collection of carefully designed hops, jumps and upper body exercises performed with great speed and intensity.
Traditional Weight Training
Traditional weight training develops strength, but is not optimal at delivering the speed and power that excellence in most sports or physical activities demands (3). The ability of plyometrics to develop speed and power above and beyond traditional weight training is what makes this style of training a crucial variable in almost any successful sports conditioning program, from football to ping pong!
So what makes plyometrics different from traditional weight training? Traditional weight training has a reputation as being the most effective form of exercise for developing strength and lean body mass. Although weight training is very effective in these categories, it is not all that effective at delivering sport-specific speed and power.
One of the reasons for this is that weight training does not mimic specific sports movements closely. Even with the use of free weights, there is still a limitation as to how closely weight training exercises can mimic the specific movements done in sport. In addition, the large loads used in traditional weight training limit the speed of movement, preventing quick and explosive movements. Doing exercises at a slow speed does little to mimic most sport activities which are done in a quick, explosive manner (1).
On the other hand, plyometric exercises are designed to be more similar in form to sports-specific skills and involve light resistance to allow for explosive speed. It is for these reasons that plyometrics can do much more for improving sport-specific speed and power than weight training alone (1).
It is important when deciding to incorporate plyos into a training program to keep in mind that some sports do not require much agility and speed.
An athlete involved in a slower, highly endurance sport such as marathon running would not benefit much from plyometric training. It is up to the trainer to analyze the needs of an athlete's sport and decide if speed, power and agility are major demands in the activity (2). Functionally, all plyometric exercises involve the same quick eccentric or "loading" phase of the movement followed by an explosive concentric or "unloading" phase. It is this quick loading or "pre-stretch" of the muscle and surrounding connective tissue that makes plyometrics so effective at developing speed and power. When the muscle is "overloaded" in this fashion through plyometric training, it becomes more efficient at producing speed-strength (power).
Physiologically, plyometrics work by harnessing both the stretch reflex and the elasticity of the connective tissue in and around the muscles during this "stretch". The stretch reflex is the reflex contraction of a muscle in response to an applied stretch. When the muscle is stretched or "loaded" at the end of the eccentric phase of a plyometric drill, the muscle will reflexively contract. This reflex contraction aids in the total force production during the concentric or "unloading" phase (2).
In addition to this, the recoil of the elastic connective tissue around the muscle after being stretched gives even more of a boost to force production during the unloading phase. The end result of these two added forces in conjunction with an all out physical effort by the athlete means up to twice as much force production in the motion than would be possible without this "pre-stretch".
For example, you will find that you can jump higher when you jump off a chair, land into a squat and then spring up as quickly as possible than you could if you just jumped from a fixed squated position on the floor.
Utilizing Plyometrics
Without question, the most commonly executed plyometric drill is the depth jump (see illustration to the right). Although it is unclear whether this jump improves vertical jumping ability, it has been found to increase leg strength and power when done alone or with a weight training program. The exercise is performed by stepping off a box and jumping immediately upon landing. Optimal box height ranges from .4 to 1.1 meters depending on the condition and experience of the athlete. The athlete's center of gravity should always be within his/her base of support with the shoulders over the knees when performing this exercise (2). Any sport requiring sprinting or jumping would benefit from this drill. |
The Depth Jump |
There is one potential drawback to plyometric training. There is a higher risk of injury due to the heavy loads applied to the muscle and tendons when compared to traditional weight training. Always make sure that the client or athlete you are working with has a sufficient level of strength and general fitness before incorporating plyometrics into their training and always progress conservatively (2). It is highly recommended that you read more about plyometrics then just this article before attempting to perform or teach them.
Plyometric training is a useful tool to increase the effectiveness of a training program for a sport or activity requiring speed and agility. In addition to the depth jump, there are many forms of plyometric exercises for any sport or activity, including activities for the arms and upper body. Sports like track and field, baseball, football, soccer, volleyball, tennis, rugby and golf are perfect candidates for improved athletic performance through plyometrics. Due to the potential for injury and numerous different types of plyometrics available, it is advisable to read more literature on plyometrics if you plan to use them in your training.
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References
- Chu, Donald. Plyometric exercises with the medicine ball. Livermore, CA: Bittersweet. 1989.
- National Strength and Conditioning Association, Essentials of Strength Training and Conditioning. Champaign, IL: Human Kinetics. 1994.
- Smythe, Randy. Plyometrics: an illustrated guide. Portland, OR: Speed City, 1987.