What phase of plyometric movement is also referred to as electromechanical delay?

Plyometric exercise refers to activities that enable a muscle to reach maximal force in the shortest time possible.[1] (See power). Plyometrics cause a muscle to stretch rapidly prior to contraction to perform movement (countermovement); this process is called the stretch-shortening cycle, or SSC.[2][1] The stretch shortening cycle is a combination of eccentric-concentric contractions which functions by integration of the golgi tendon organ (GTO) and the muscle spindle. There are three phases in a plyometric sequence: the eccentric phase, or landing phase; the amortization phase, or transition phase; and the concentric phase, or take-off phase. Plyometrics exercises are based on the understanding that a concentric (shortening) muscular contraction is much stronger if it immediately follows an eccentric (lengthening) contraction of the same muscle. In addition to this, plyometric drills can closely mimic both the movement pattern and the speed of execution of actual sports performance, as opposed to traditional resistance training.[3]

Phases

• Eccentric Phase

The eccentric phase, or landing phase, involves the preloading of the agonist muscle group. During this phase, elastic energy is stored and muscle spindles are stimulated. An example of this is the portion of the squat jump from when the feet come into contact with the ground to the bottom of the movement (landing).

• Amortization Phase

The amortization phase, or transition phase, is the time between the concentric and eccentric phases. This phase of the stretch shortening cycle is perhaps the most crucial in production of power as the duration of amortization must be kept at a minimum. If the transition phase lasts too long, the energy stored during the eccentric phase dissipates, thereby negating the plyometric effect. Then it becomes just a standard exercise.

• Concentric Phase

The concentric phase, or take-off phase, is the response to the eccentric and amortization phases. During this phase, elastic energy is utilized to increase the force of the subsequent movement or is dissipated as heat. The force is increased beyond that in isolated concentric muscular action. An example of this is the explosion out of the bottom portion of a squat jump into the jump itself.

Integration of Plyometrics Training

With regards to integrating plyometrics into programs, studies have shown that contrast loading or "complex training", which involves lifting at >85% of 1RM on a strength exercise followed by an explosive exercise or load of around 40% 1RM, is more effective at producing enhanced power output than constant loading (when the weights stay the same).[4] Some authorities recommend that an athlete should be able to half squat at least 1.5 times their body weight before undergoing a plyometric program, but other claim this may be excessive.[3] Plyometric training can also be periodized just like any other type of training.

Resistance training plays a vital role to play in laying the foundations for greater power (power = strength x velocity) and pre-conditioning an athlete for plyometrics. Resistance training can facilitate a larger and stronger muscle, which will be able to generate greater force plyometrically; additionally, strengthened tendons and muscles will be less prone to strains and pulls.[3]

The volume of plyometrics training during a session is inversely proportionate to the intensity of the plyometric exercises (intensity measured in foot contacts); the more dynamic the move and the greater the power generated, the fewer foot contacts are required.[3]

Etymology

The term plyometric is a combination of Greek words that means to increase measurement--plio, which means "more", and metric, which is "to measure".

Inventor

//www.verkhoshansky.com/

See Also

• Circuit Training
• Pyramid Training
• Interval Training
• Cross-training
• Split Routine
• Superset
• Staggered Set
• Combo Lifting

References

1. ↑ 1.0 1.1 National Strength and Conditioning Association (2000). Essentials of Strength Training and Conditioning, 2nd ed., Champaign, IL: Human Kinetics. 
2. ↑ McNeely/Sandler (2007). Power Plyometrics: The Complete Program, 1 ed., UK: Meyer and Meyer Sports. 
3. ↑ 3.0 3.1 3.2 3.3 Shepherd, John (n.d.). Plyometric Exercise and Power Training. Power Performance. Retrieved on 2008-10-05.
4. ↑ Brandon, Raph (n.d.). Power Training: How contrast power training maximises performance. Power Performance. Retrieved on 2008-10-05.

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