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Factors that contribute to power development

This is an excerpt from Complete Conditioning for Hockey by Ryan van Asten.

Because the athlete’s strength levels provide the foundation for power production, many of the factors associated with increases in strength, outlined in chapter 5, also have a significant influence on power development. These factors include neurological, muscle size, and muscle fiber type adaptations. But developing maximal force alone is not necessarily rate dependent. However, the ability to modify the force–velocity relationship will significantly affect the athlete’s power. If one can move the same amount of weight in less time (higher velocity), power will increase. In contrast, during the skating stride, the key is to maximize force production in relation to time; this is known as impulse. In addition to impulse, factors such as the stretch-shortening cycle (SSC) and elastic energy also contribute to power production in hockey.

In contrast to sprint running, the impulse during the skating stride is much larger. This fact is related to the difference in ground or ice contact times between the two. During skating, ground contact times are up to four times longer than during sprint running. Since force production is not constant throughout the skating stride, impulse might be the best metric in determining performance. However, Taber et al. (2016) suggest that the duration of time in which forces are applied is only slightly modifiable; therefore, the total force must be increased during the action to improve impulse. Methods to improve impulse are described later in this chapter.

Stretch-Shortening Cycle
The stretch-shortening cycle (SSC) is characterized by a rapid cycle of eccentric muscle contraction and a short transition period to concentric muscle contraction. Imagine a countermovement jump, where there is a quick transition between the lowering and propulsion phases. The SSC is a significant contributor to performance in this movement. During the lowering phase, the muscle is stretched rapidly and quickly shortens to produce the power required to jump. There are three primary mechanisms responsible for the SSC. These include neurological mechanisms in the muscle, elastic energy, and the development of active state.

Neurological Mechanisms
Within the muscle, receptors analyze the rate of stretch on the muscle and the magnitude of the tendon’s stretch. These receptors are known as the muscle spindles and Golgi tendon organs, respectively. The reality is that these receptors act to protect the muscle from being overstretched, which could result in injury. However, they will also act in conjunction to generate a more forceful concentric contraction. When a muscle stretches rapidly, the spindles sense this rate and interact with the nervous system to create a reflex that causes the muscle to contract involuntarily. An example of this is when a doctor strikes the tendon in one’s knee with a rubber mallet. This procedure induces a rapid stretch in the quadriceps, inducing a kicking reflex. This stretch reflex also applies to sports performance when landing from a jump or running to generate rapid force production. If the Golgi tendon organs perceive too much stretch, they will force the muscle to shut down. Proper training can enhance the effects of muscle spindles and minimize the Golgi tendon organs’ effects.

Elastic Energy
The best way to describe elastic energy is to think about a rubber band. When a rubber band is stretched, it begins to store energy passively, which is known as potential energy. This stored energy is then converted to kinetic energy (energy in motion) when the elastic is released, and the band will rapidly return to its initial state. Think of tendons as rubber bands. When one lands from a jump, one’s tendons are stretched, storing energy that can then be used to contribute to rapid force production.

Active State Development
Active state is characterized by the formation of cross bridges within the muscle fibers. These cross bridges are where muscle contraction occurs at the most basic level and are the points at which the thick and thin filaments of the muscle fibers attach. It has been shown that active state is enhanced during the eccentric (or lowering) portions of a movement (e.g., during the lowering phase of a countermovement jump). The more cross bridges that are formed, the more force that can be generated.