Plyometrics or plyometric exercises are a form of strengthening exercise, incorporating jumping, bounding and hopping movements, which works to increase power in the muscles. Power is used in the vast majority of all sports and so plyometrics can be used to help develop this for most athletes.
Below are a few very basic plyometric exercises using hoops which are good for the later stages of rehabilitation. More advanced exercises may be used for improving sports performance. Plyometrics is an advanced training technique, which should only be used by experienced athletes who have already developed their basic strength.
How does Plyometrics work?
Plyometrics work to develop a stronger and faster muscle contraction, through using an eccentric muscle contraction, immediately followed by a concentric contraction. For example, a common plyometric exercise is the depth jump. This involves jumping off a box, landing on both feet in a squatting position, before immediately jumping straight upwards. This helps to develop power in the quadriceps muscles (amongst others) as landing into a squat position involves an eccentric contraction of the quads to decrease rapid knee bending, before a concentric contraction to straighten the knees and jump up.
Eccentric contractions produce the maximum amount of force. Therefore when the muscle contracts like this (lengthening rather than shortening), the maximum amount of energy are produced. This is stored by the elasticity of the muscle. This energy is only available for the subsequent contraction and so a concentric contraction must occur as soon as possible to take full advantage of this stretch-shortening cycle.
As already mentioned, depth jumps and box drops are popular exercises. To work more on the forward motion, bounds and hops should be used. Plyometrics can also be used for improving power in the upper body for sports such as athletic throwing events. These often involve medicine balls which when caught require an eccentric contraction to control the motion, followed by a concentric contraction to throw the ball back. Push-ups with a clap can also be used. The downward phase of a push-up involves an eccentric contraction of the chest muscles, which is immediately followed by a strong concentric contraction to push back up and clap the hands.
What are the risks?
Plyometric training does carry a high injury risk due to its explosive nature. For this reason, athletes should first develop a base level of strength through a standard resistance programme. Plyometric sessions should be performed a maximum of twice a week and not when the athlete is tired from previous workouts. A thorough warm-up and cool down will also help to prevent injuries, as will a gradual development of the intensity of the exercises performed. Delayed onset muscle soreness is a common complaint.