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PNF Stretching
PNF Stretching PDF (not all-inclusive)
| Question | Answer |
|---|---|
| What are proprioceptors? | Specialized sensory receptors located within joints, muscles, & tendons |
| What do proprioceptors do? | Relay info concerning muscle dynamics to conscious & sub-conscious parts of our CNS |
| Processing of proprioceptive information | Most is processed at the sub-conscious levels so we don't have to think about tasks such as maintaining posture or position of our body parts |
| What 5 components are involved in reflex arcs? | Receptor Sensory neuron Integration center Motor neuron Effector |
| What is the receptor? | Site of stimulus action |
| What is a sensory neuron? | Transmits afferent impulses to the CNS |
| Simple reflex arc? | Single synapse between a sensory (afferent) neuron & a motor (efferent) neuron- monosynaptic |
| Complex reflex arc? | Multiple synapses with chains of interneurons- polysynaptic reflexes (withdrawal or crossed-extension) |
| Parts of a Muscle Spindle | 3-10 infrafusal fibers, which provide input to regulate the activity of muscle. Extrafusal fibers are effective & when stimulated, they contract, shortening the muscle |
| What influences the muscle spindle? | Rate & degree of stretching |
| What does stretching do to the muscle spindle? | Increases tension & increases rate of action potential generation. |
| Muscle Contraction | Reduces tension on the spindle & lowers the rate of action potential generation |
| What happens when impulses from mm spindles are transmitted at a high frequency? | Extrafulsal fibers are excited, causing the muscle to contract This contraction attempts to prevent the muscle from stretching any further |
| Afferent Impulses | Travel to the spinal cord, synapse with motor neurons & interneurons. Motor neurons send activating impulses to agonist, causing contraction preventing any further stretch. |
| Interneuron Synapse | Inhibits action of the antagonist, which effectively prevents antagonist from resisting contraction. This is called reciprocal inhibition. |
| Where are GTOs located? | Tendons near the musculotendinous junction |
| How is a GTO activated? | Muscle stretch. As muscle tension increases, impulses from the GTO increase. Neural input from GTOs inhibits muscle activation |
| GTOs send afferent signals to CNS interneurons to perform 2 functions. What are they? | Inhibit motor neurons serving the contractile muscle (autogenic inhibition); Stimulate motor neurons serving the antagonistic muscle group |
| Overal, what happens because of the GTO reflex? | Contracting muscle relaxes & lengthens as the antagonist contracts & shortens |
| What is reciprocal inhibition? | Relaxation that occurs in the muscle opposing the muscle experiencing increased tension |
| What is autogenic inhibition? | Relaxation that occurs in the same muscle experiencing increased tension |
| What is disinhibition? | Ability of motor cortex to override autogenic inhibition |
| How does PNF compare to other types of stretching? | PNF is superoir for increasing ROM when compared to static/passive & ballistic stretching, esp. in respect so short-term gains. PNF is more engaging & less boring. |
| How many repetitions of PNF should be performed to achieve the greatest gains? | at least 4 |
| How long should contractions be held in a PNF stretch? | 3-10 seconds |
| What is the optimal contraction intensity in PNF stretching? | 65% of maximal voluntary isometric contraction |
| Hold-Relax Stretching | Range-limiting mm is lengthened to point of limitation; Pt performs sub-max isometric contraction for 5-8" then relaxes; Limb is passively moved into new range as the muscle is elongated |
| Contract-Relax Stretching | Same as hold-relax, except instead of an isometric contraction a strong, small range isotonic contraction of the restricting mm (5-8") is performed. Rotation should be allowed during contract-relax. |
| What is the aim of contract-relax? | Take advantage of autogenic inhibition from GTOs |
| When should hold-relax be used instead of contract-relax? | Acute injury or if active ROM is painful; If contraction of restricting mm is too painful/weak, can reverse the direction of contraction |
| Hold-Relax with Agonist Contraction | Mm lengthened to point of limitation; Pt performs sub-max isometric contraction b/t 5-8"; Limb actively moved by pt into new range via concentric contraction of mm opposite range-limiting mm |
| What type(s) of inhibition is used by hold-relax with agonist contraction? | Autogenic & Recriprocal; Agonist contraction may also be useful for initiating neuromuscular control in newly gained ROMs. |
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