Plyometric training, which includes both "jump" training and use of the medicine ball for upper body exercises, is a system of exercise that has become a bit controversial. There have been writings in which the authors claim the system is "dangerous", or "ineffective". How can the coach or athlete make sense of all the different points-of-view?
In order to decide if this program is for you it would be advisable to conduct a "Needs Analysis" as described by Fleck & Kraemer (1).
This process allows the coach to look at the variables associated with designing a proper training program for their athletes. Among the variables that need to be considered are the:
- Exercise Movements - the coaches must ask themselves about the following:
- Specific muscles - which muscles are the primary muscles to be developed for the specific sport?
- Joint Angles - at which angles are the joints as the athlete performs their most demanding activities?
- Contraction Mode- are the muscles required to deliver explosive movements (i.e. jumping) or a more sustained contraction (i.e. swimming)?
- Loading Needs - the forces to be overcome by the athlete in the course of their event or sport are also important considerations. As an example, the sumo wrestler and American football lineman must overcome tremendous forces to be successful, while the tennis player uses a 10-12 ounce racquet to change the direction of the tennis ball.
Considering each of these factors allows the coach to answer the questions that revolve around which muscle groups need to be trained and how they should be trained. If explosive movements are involved in the sport, then plyometrics are a must.
Coaches need to understand where their sport falls in terms of the physiological demands. Since plyometrics can be considered a short term activity it falls into the anaerobic system of metabolism.
Thus it is important that it fit into the overall demands of the sport.
- Metabolism Used / Estimated Percentage of Contribution From:
- ATP-PC Source - this energy system is concerned with quick, bursting contractions such as the sprinters start, or the divers take-off. Most plyometric training programs fall into this category, largely because of the recovery or rest allowed between each exercise bout.
- Lactic Acid Source - this energy system is utilized by the athlete involved in events that generally last from 30-45 seconds. It also has an effect on the Aerobic system in increasing the speed capability of the 1500 meter runner.
- Oxygen Source - this energy system is associated with the endurance athlete and is not necessarily compatible with plyometric training. Although it is not unusual to see distance runners using bounding as a means of gaining variety in their programs.
The physiological demands of a particular sport -- such as aerobic or anaerobic endurance -- must be considered in the designing of a training program. For example, if your sport requires contribution from the lower extremities then there may be potential for the use of plyometrics, but let us look closer. If the sport requires speed of movement, quick starts and stops, or changes-of-direction then the plyometric program begins to actually fit the sport. If the sport requires a singular burst or performance such as the "punch" in a vault, or a take-off in the long jump, then plyometrics are also definitely for you. If the event requires many repetitive motions of less than maximal effort, such as a triathlete might experience, then the purpose of including plyometric training becomes less important. Once the coach has gone through the process of a "needs analysis" they can feel confident assessing the importance of plyometric training for their athletes.
One of the major reasons for using plyometric training is the reduction of the "amortization" phase of landing. The amortization phase is described as the time from the onset of eccentric (decelerating) muscular contractions to the onset of the concentric (accelerating) contractions during the landing-stance-take-off phases in running or jumping. The shorter the ground contact time, the more efficient is the athlete in reducing the amortizaton phase.
Depth jumps are one of the exercises used when assessing the amortization phase.
When observing runners the amortization phase corresponds to the translation of the body’s center of gravity (COG) during linear movement. The COG of the body is seen to undulate during the landing, stance and take-off phases of gait. The COG moves up and down according to the athlete’s ability to initiate the eccentric-concentric phases of muscle contraction. An athlete who has developed eccentric strength will be able to control and reverse the decent of their COG during running more effectively than a non-trained individual. The smoother the path of the COG in running, the more efficient the athlete will be -- thus maximizing their potential for speed.
Looking more closely into this situation one must consider the forces that are developed during running. As the runner pushes against the ground, they receive forces back from the ground that are generally equal to the pushing force. This allows the runner to overcome their own inertia or weight and start themselves in motion.
Forces are then directed in both a vertical and horizontal direction the results of which accelerate the athlete forward. Each time the foot makes contact with the ground, the toes, mid-foot, and ankle flex and extend dissipating the forces that come from the ground. The more flexible the foot, the more the forces are spread out through the soft tissues (muscles, tendons, ligaments) and the less the forces can be used to drive the body forward. The result is that the foot will remain in contact with the ground for a longer period of time. A general observation is that "good athletes do not spend a long time on the ground".
The firmer the foot and ankle, the less the forces are dissipated and the more they are transferred through the ankle to the knee and hip areas. These forces can then be used to produce a short ground contact time and more complete use of the forces derived from pushing against the ground. The result then is a "quicker" athlete, more capable of faster leg turnover (frequency). There are several plyometric drills than can be used to help strengthen this area. They include:
- Two Foot Ankle Hop – Start with the feet shoulder width apart and the body in a vertical position. Using only your ankles to provide momentum, hop continuously in one place. Extend the ankles into their maximum range on each vertical jump.
- Single Leg Ankle Hop - The action is the same as in the previous exercise with the difference is that the hops take place off of one foot. Each of these exercises should be performed over a distance of 10-12m, 3-5 times.
- Hexagon Drill- Form a hexagon on the floor using tape to mark each side. Make sure each side is 24" in length. Stand in the center of the hexagon with you feet shoulder-width apart. Jump across each side of the hexagon and back to center, then proceed around each side of the hexagon. This may be done for a specific number of complete trips around the hexagon (3 times) or for a total amount of time (30 seconds).
These exercises are just a sample of the drills that can be used under the title "Plyometrics" to help develop a specific skill that an athlete might need for their sport. Every coach and athlete can determine if their sport will benefit from plyometric training by performing the simple "needs analysis" mentioned earlier.
One of a multitude of plyometric floor-patterns that can be taped onto the floor.
The final stage of determining if plyometric training might be helpful for a particular sport is to examine the primary sites of injury for a particular sport. Injury prevention is always a critical issue in the overall success of a team or individual athlete. Using plyometrics to prevent injuries is possible. It stands to reason that the better prepared an athlete is the less likely they are to fall victim to injuries in practice or competition. However, of greater note is that plyometrics may help in determining whether someone is ready to return to play or not. Coming off of an injury there are certain criteria that can be used to determine if an athlete is ready to fully practice or perform. An example of how plyometrics can be used in this fashion would be to perform a series of cone drills after sustaining a knee or ankle injury. Assuming the athlete has recovered and begins to return to walking, or jogging. The next phase is to test the athlete to see if they can perform the cone drills without pain or impairment of function. The following represents the way in which the athlete would be tested:
CONE DRILLS to test:
Space six (6) 12-18" tall cones approximately 1m apart. Hop forward, spending a minimal amount of time on the ground between cones. Note that the athlete lands equally on both feet and jumps from both feet after landing.
Above athlete bounding through a series of small hurdles – an expanded variation of the cone drill.
Repeat as above, moving through the cones in both, left and right, directions.
Using the above set-up of cones, hop forward over the first cone, then backward over the same cone. Hop Forward over two cones, then back one, forward over two, and back one. Repeat to finish.
Hop laterally over cones with both feet; change direction at the end of the cones and hop back through. Change directions at the other end and hop back through. The athlete will then have traveled through three times total.
Note: Variations include landing on one foot to accomplish the change of direction.
In summary, plyometrics make sense as a form of training for sport performance. They are not only a training exercise, they also can be used to teach a particular athletic skill, and they can function as a method for testing an athlete’s readiness to return to play following an injury. A particular system of exercise such as plyometrics is not dangerous in and of itself. It only becomes a risk to perform these exercises when the administrator of the program is lacking in knowledge and creates a situation that is dangerous or excessive in terms of physical stress. This article is intended to help the participant understand the methods, uses and program designs for proper usage of plyometric training.
- Chu, D.A. (1992). Jumping into Plyometrics. Human Kinetics, Champaign, IL.