VISCOELASTICITY: FLEXIBILITY Is SPEED SPECIFIC

The belief exists that if we maintain a certain pull length on the rubber band for an extended time (say at 35 units), the rubber band will begin to deform permanently, and as a result lose SEE as it loses its degree of elasticity. This region of training is known as viscoelasticity: having a combination of viscosity and elasticity.

Viscoelastic materials have time dependent mechanical properties, being sensitive to the duration of the force application. Such materials will continue to deform over a finite length of time, even if the load remains constant, until a state of equilibrium is reached (also known as the “creep effect”).

High temperatures increase the rate of creep and low temperatures decrease it. For the most effective use of this property, the material to be deformed should be warmed and then have a sufficient load applied over a long period of time. Different tissues respond differently to various rates of loading. When loaded rapidly, they exhibit greater resistance to deformation than if they are loaded slowly.

This is why dynamic flexibility cannot be gained through static stretches. Flexibility is speed specific. The stretch reflex engages whenever a muscle is stretched suddenly or dramatically, or both. This mechanism is controlled by the muscle spindles, which are two special receptors that activate the stretch reflex. One of these is sensitive to stretch magnitude and the other is sensitive to speed and magnitude. The prevalent static stretch mayor may not reset the first receptor, but it is completely ineffective for the latter. As a result, flexibility is speed specific.

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