In the first post on Strength & Conditioning, we focused on Pulse Raising and the concept of warming-up. This was similar to sifting through the lower gears of your vehicle. The aim of this post is to take you thorough how one should hit top gear (which corresponds to the maximum intensity of the exercise). This can be achieved through Plyometric exercises.
Plyometrics exercises include activities that enable a muscle to reach maximal force (maximum force that can be generated at one go) in the shortest possible time, i.e. explosive power. Plyometrics is a combination of (plio= more; metric= measure).
Just as a spring bounces off after being compressed and released quickly, our muscles also store energy when stretched and deliver the energy in the subsequent movement. This is the essence of a plyometric exercise. Let us take the example of jumping with both feet on to a higher platform. We break this activity into 3 steps and see how it corresponds to the above activity.
1. Eccentric phase:
This phase enables the muscles to store energy. This involves preloading the intended muscle(s) (in this case, the calf muscles) by going into a semi-squat kind of a position. This stretches our calf muscles and they are loaded with some potential energy.
2. Amortization phase:
This phase involves the transfer of energy stored in the first movement to the release of energy achieved by a counter-movement. This phase needs to be very short-lived and usually has the duration of a fraction of a second.
If you release a coiled spring too slowly it will not bounce as much. If you release it too quickly, it may not be able to load the entire energy required for maximum release; hence the extremely short duration.
3. Concentric phase:
This is the phase wherein the jump takes place with the help of the energy loaded onto the calf muscles. It involves the muscle’s response to the previous 2 phases. In this phase, the energy stored during previous 2 phases is used to maximize the force in the subsequent counter-movement.
Plyometric exercises are not inherently dangerous; however, as with all modes of exercises, risk of injury exists. There should be a pre-training assessment of the athlete before commencing a program comprising plyometric drills. The athlete should have a minimum base of strength, speed and balance and must understand proper plyometric technique.
We recommend the following levels of fitness for different parameters before you get into plyometric exercises.
a) Lower body plyometrics: The athlete should be able to lift a weight of at least 1.5 times her/his body weight in a single squat movement.
b) Upper body plyometrics: One-time bench press with a maximum weight equal to or more than the athlete’s body weight.
a) Lower body plyometrics: Minimum of 5 repetitions of squat with 60% body weight in 5 seconds or less.
b) Upper body plyometrics: Minimum of 5 repetitions of bench press with 60% body weight in 5 seconds or less.
The athlete should be able to stand on one leg for 30 seconds without falling.
Plyometrics should be considered not an end in itself, but as a part of an overall program that includes strength, speed, aerobic and flexibility training along with proper nutrition. Frequency of plyometric training sessions per week typically ranges from 2-3 times per week, depending on playing-season and time of year.
Since these are high intensity exercises, adequate recovery should be provided between the sets and sessions. 2-3 minutes of rest between the sets and 2-3 days of gap between the sessions should be provided. A proper warm-up routine should be performed before commencing a plyometric session. Warm up drills may include: marching, jogging, skipping, footwork and lunging. (For more details on warming-up, please read http://blog.sportingethos.com/?p=38)
Some examples for lower body plyometric exercises are:
1. Squat jump 2. Skip Power
3. Split squat jump 4. Backward Skip
5. Double-leg tuck jump 6. Box drills
7. Pike jump 8. Depth Jumps
Examples for upper body plyometric exercises are:
1. Chest passes 2. Hand overhead throw
3. Single arm throw 4. Depth push-ups
Manual of Strength Training & Conditioning, 3rd edition (NSCA)
Jumping into plyometrics, 2nd edition (Doland Chu)
Exercise physiology, 6th edition (Katch & Katch)
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