# Power

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 Power:  The ability of a muscular unit, or combination of muscular units, to apply maximum force in minimum time.  .

Power, in physics, is the "rate at which work is performed," i.e. work is the "product of force and distance" (Work = Force x Distance). [1]
$P = \frac{W}{t}\,$

In mechanics, the work done on an object is related to the forces acting on it by

$W = F \cdot \Delta s \,$

where

F is force
Δs is the displacement of the object.

What this usually translates to is the ability to exert maximum muscular contraction instantly in an explosive burst of movement, ie. the ability of a muscular unit, or combination of muscular units, to apply maximum force in minimum time.[2] The two components of power are strength and speed, as with power exercises. (e.g. jumping or a sprint start, snatch, clean and jerk, etc.) [3] Power is a vital component of motor fitness, and is applicable especially to a myriad of athletic activities, and therefore it should not be neglected. Despite the importance of power for athletics and function, the ability to produce powerful muscle contractions decreases with age, more so than other components, such as cardiorespiratory endurance. This decline also appears despite persistent training and otherwise good health.[4]

For a program which includes power training to achieve maximum effectiveness, a strong initial focus should be on maximizing strength. For example, to experience the greatest improvement in speed and explosiveness when undertaking an explosive-type training program which includes plyometrics, athletes should first have a strong strength base. Undertaking a plyometric program without first developing greater levels of strength may make an athlete more explosive and quicker but not to the extent if the program had first focuses on increased levels of strength.[5] One must also take into consideration, however, the force-velocity curve when considering a optimum balance between strength, speed, and power. Most athletic movements do not involve slow contractions at near maximum force, but are characterised by mid-to-high velocity.

## Measuring Power

As mentioned, power is a product of force times distance over time. To quantify power output, numbers need to be consistent in the form of SI units, and the result is measured in watts. SI units are as follows:

Distance in Meters

Mass in Kilograms

Force in Newtons (A newton is the force required to accelerate 1kg 1 meter per second per second. For practical purposes, this equals 9.8kg)

Time in Seconds

Work in Joules (newton * meters)

Power in Watts (joules/seconds)

Example: Determine the power output of an athlete who lifts a 50kg weight, a height of one meter, for eight reps, in 40 seconds:

Newtons = (50kg*9.8m/s) = 490n

Joules = (490*1m)= 490nm

Watts = 490nm/40s = 122.5 * 8reps = 980w

(When measuring watts through a rotatary activity, work is expressed as torque (in newton meters) times the angular displacement in radians (1rad = 180/π). The distance unit is the length of the moment arm.)

Using the formulation for wattage, different activities can be compared one to the other in similar terms.

## Enhancing Power

Many methods have been employed in attempts of enhancing power; some methods include incorporation of explosive lifts, such as Olympic Lifts, into routines to incorporation of plyometrics. 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.[6]

### Plyometrics

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).[7] 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.[6] 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.[6]

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.[6]

## Featured Pioneer...

Professor Yuri Verkhoshansky is the Russian scientist who pioneered plyometric training as a means of sports training to improve athletic performance, mainly speed-strength. Widely known as the "Father of Plyometrics", he has been the leading researcher and coach most recognized with the spread of plyometrics training. Verkhoshansky’s first research study on plyometrics was published in 1964, but he had been researching the subject for several years before then as part of his post-doctoral work.

## Featured Article

Plyometric exercise refers to activities that enable a muscle to reach maximal force in the shortest time possible.[8] (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.[9][8] 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.[6]

## 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).[7] 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.[6] 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.[6]

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.[6]

## 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".

## Featured Resource

Template:Featured Power Resource

## References

1. EliteTraining.com. Improving Athletic Power. Bodybuilding.com. Retrieved on 2008-03-09.
2. About CrossFit Champions. CrossFit Champions. Retrieved on 2008-04-11.
3. Brian Mac. Components of Fitness. Retrieved on 2008-03-08.
4. Unk. (n.d.). Power v endurance: what goes first in the ageing stakes?. Power Performance. Retrieved on 2008-10-05.
5. Yessis (2008-03-12). The Yessis System Of Improving Athletic Performance. Dr. Yessis.com. Retrieved on 2008-10-03.
6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Shepherd, John (n.d.). Plyometric Exercise and Power Training. Power Performance. Retrieved on 2008-10-05.
7. 7.0 7.1 Brandon, Raph (n.d.). Power Training: How contrast power training maximises performance. Power Performance. Retrieved on 2008-10-05.
8. 8.0 8.1 National Strength and Conditioning Association (2000). Essentials of Strength Training and Conditioning, 2nd ed., Champaign, IL: Human Kinetics.
9. McNeely/Sandler (2007). Power Plyometrics: The Complete Program, 1 ed., UK: Meyer and Meyer Sports.