by Charles Poliquin ~ source
Speed and PowerIf you want to get more powerful and improve your performance, you must be strong. But you must also be able to use that strength with the greatest efficiency. This article will tell you how to do this.
Power is the product of strength times speed. Although building strength and increasing your speed contribute to greater power, an increase in one doesn’t necessarily mean you will produce greater power. Seems confusing, no?
It doesn’t have to be. The development of power requires an understanding of the mechanical and neuromuscular factors that can be trained with programs targeted at moving heavy weights quickly, whether they be barbells in a weight room, or an opponent on a playing field. A new report presented at the 2012 International Conference of Strength Training in Oslo, Norway provides strategies for to help you get more powerful.
Researchers from Edith Cowan University in Australia discuss the development of power through neural, hypertrophic, and mechanical adaptations due to training. They then provide examples from their own research on trained and novice athletes.
First, neural factors that contribute to power output include motor unit recruitment and the preferential recruitment of fast-twitch fibers. They occur relatively quickly in response to training (within 2 to 4 weeks). Performance adaptations are also lost quickly in response to detraining or incongruent training, like endurance exercise. For example, sequencing a power training cycle followed by a distance running cycle would be a very bad idea for any athlete that must produce force at a high velocity.
Second, intramuscular factors that respond within a few training sessions include alteration in fiber type expression and a more favorable muscle enzyme concentration for the generation of maximal power.
Third, mechanical factors such as muscle and tendon architecture significantly influence power and rate of force production. Increased cross-sectional area of the muscle, changes in pennation of the muscle, and greater tendon elasticity all contribute to greater power output.
Tendon behavior in particular was found to adapt as follows: During loaded ballistic movements with the intention to accelerate as fast as possible, such as the concentric phase of a front squat, the tendon of the knee extensors behaves as a “power amplifier” but changes to a rigid “force transducer” at heavier loads.
Following a training study comparing heavy back squatting with jump squats on tendon architecture, the heavy training program caused increased tendon stiffness and the power program produced more elasticity.
Fourth, the Stretch Shortening Cycle (SSC), which involves both the mechanical and neuromuscular factors already mentioned, is the basis of almost all human movement when the intention is to maximize efficiency. Simply, the SSC involves a countermovement that stores elastic energy in the muscle and tendon unit, allowing for greater acceleration in the concentric or shortening phase of movement.
The classic example is a basketball player dipping downward with a countermovement before exploding upward in a vertical jump. Taking advantage of the SSC with a fast countermovement can increase the speed of the concentric movement by 10 to 15 percent.
There are four principal mechanisms that influence the SSC:
1.) The preload during the eccentric countermovement phase allows for near maximum force generation at the point of change over from negative to positive movement. The resulting power is much higher than if a concentric only movement was performed. For example, consider how much higher you can jump with a countermovement than if you start from a static squatting position. The static squat jump eliminates the preload.
2.) There is a complex interaction of the muscle and tendon unit during the SSC leading to increased power. During the countermovement eccentric phase, the muscle tendon unit (MTU) stretches under high tensile forces and is primed to maximize force output. As tension builds in the agonist MTU, the system experiences a high acceleration, which quickly slows, stops, and reverses the direction of movement. The MTU then recoils after being stretched (similar to a rubber band), allowing for greater power output.
3.) The storage and recovery of elastic potential energy enhances force generation during SSC movements. Researchers highlight that there are elastic mechanisms in the tendon, the muscle myofilaments, and muscle connective tissues that enhance the recoil effect of the MTU.
4.) The stretch reflex is activated during the rapid lengthening of the MTU. Through a spinal loop, neural impulses result in the generation of greater force output.
Fifth, the strength threshold tells us that power is maximized when using a load that is one-third of the maximal load (1RM load). Therefore, the stronger you are, the greater possible power output. Researchers suggest that maximal strength should be three times the load that must be accelerated for optimal power output. For example, you should have the capacity to back squat more than two times body weight if you are to optimize strength for vertical jump performance.
Results of training studies comparing power and strength training show that the most effective training method is contingent on the relative strength of the athlete. For example, in a study using relatively “weak” athletes who had an average 1RM squat of 1.3 times body weight, 10 weeks of either power or heavy strength training produced similar power improvements. Neither method was found to be significantly better for increasing power because the athletes were relatively untrained and will therefore respond to a wide range of stimuli.
A second study compared the effect of power training in relatively “strong” athletes with an average 1RM squat of 1.9 times body weight and “weak” athletes with the average 1RM squat of 1.3 times body weight. Results showed that although both the strong and weak groups did the same power training, the stronger athletes had a much larger improvement in power output.
Researchers conclude that for long-term athlete development, it is best to build a high level of strength prior to implementing power training. The reason trained, stronger athletes improved more from the power training than the novice, weaker athletes was that the strong athletes utilized the eccentric phase of the SSC better and they could tolerate higher forces. This allowed them to better maximize the four potentiating mechanisms mentioned above.
Take away the following points about developing optimal power:
1) Optimal power output will be achieved with maximal strength and power training sequences, but best results will come from getting strong prior to training for power.
2) Novice and weaker individuals will respond to strength or power training with similarly improved performance. If training time allows, program to build strength prior to training for power.
3) Maximal strength is the most influential quality of the neuromuscular system.
4) Trained and stronger athletes can produce greater power in response to explosive training due to the ability to optimally utilize the eccentric phase and benefit from the SSC.
5) Tendon, contractile tissue, and muscle fiber undergo stress to elicit adaptations. Adequate recovery is necessary following power and heavy weight training. It is especially important following eccentric training.
6) Optimal lifting technique must be practiced because it will allow you to create the elastic effect and optimally utilize the eccentric phase for greater power.
7) Maximal strength in the squat is necessary for lower body power and in the bench press for upper body power, but structural balance between the agonist, antagonists, and stabilizers is equally important for maximal power output.
8) Tempo plays a primary role in the development of strength and power. If you’re not counting tempo (the time spent on the eccentric, concentric, and any isometric pauses), you will not get all you can out of your training.