I know it activates the golgi tendon, but how exactly does it allow the muscle to be stretched further?
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06-12-2011, 02:04 PM #1
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06-12-2011, 06:49 PM #2
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06-13-2011, 08:37 AM #3
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PNF stretching has two procedures, each of which involves different mechanisms to allow for the muscles to be stretched further:
Procedure 1: Contract and Relax (CR)
This involves:
-Place the limb close to the end of range
-Contract the muscle to be stretched at 50% effort for 10s
-Relax and stretch the muscle for 15s
-Repeat the process until no more gains are possible
Theory:
Muscles spindles cells located within the muscles, protect the muscle from injury. They sense how far and fast a muscle is being stretched and when activated, relay this information to the Central Nervous System (CNS), which initiates contraction of the stretching muscle; a 'stretch reflex'. This reflex causes the muscles to contract to prevent overstretching the muscle.
Located within the muscle tendon is another sensor called the golgi tendon which senses how much tension is being put upon the tendon. When the golgi tendon is activated then it relaxes the muscles (unlike the muscle spindle).
A voluntary contraction during a stretch increases the tension on the muscle, activating the golgi tendon organs more than the stretch alone. So when the voluntary contraction is stopped the muscle is inhibited from contracting against a subsequent stretch. PNF stretches uses this to take advantage of the sudden vulnerability of the muscle and its increased range of motion by using the period immediately following the isometric contraction to train the stretch receptors to get used to this new, increased, muscle length. This is accomplished by the final passive stretch.
Procedure 2: Antagonist Contract (AC)
This involves:
-Place the limb at the end of the range - so that the antagonist (e.g. hamstrings) are stretched
-Contract the agonist muscle (quads) while continuing to stretch the antagonist (hamstrings)
-Relax and stretch the antagonist (hamstrings) muscles for 10s
-Repeat the process until no more gains are possible
Theory:
When an agonist contracts, in order to cause the desired motion, it usually forces the antagonists to relax (see section Cooperating Muscle Groups). This phenomenon is called reciprocal inhibition because the antagonists are inhibited from contracting.
When stretching, it is easier to stretch a muscle that is relaxed than to stretch a muscle that is contracting. By taking advantage of the situations when reciprocal inhibition does occur, you can get a more effective stretch by inducing the antagonists to relax during the stretch due to the contraction of the agonists. You also want to relax any muscles used as synergists by the muscle you are trying to stretch.
This is a information that I learned from a Fitness and Training lecture at University - I hope it helps to answer your question.
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