Proprioceptors and Proprioceptive Neuromuscular Function

Question 1

What is PNF?

Answer 1

PNF is an advanced stretching technique which aims to improve an athletes flexibility

Question 2

What do proprioceptors do?

Answer 2

Sense organs that provide kinaesthetic feedback concerned with body movement. Send messages to brain regarding changes.

Question 3

What is the Muscle Spindle Apparatus?

Answer 3

Receptors that lie between muscle fibres, detecting the degree of stretch

Question 4

What happens if the muscle is being stretched too much?

Answer 4

The CNS sends an impulse back to the muscle to tell it to contract – triggering the stretch reflex. This reflex action that causes the muscle to contract prevents overstretching and reduces risk of injury.

Question 5

What are Golgi Tendon Organs?

Answer 5

Receptors found at the junction between muscles and tendons – detect the level of tension

Question 6

What is Autogenic Inhibition?

Answer 6

If a muscle contracts isometrically (does not change length) they sense the increase in tension and send inhibitory signals to the brain. This sends a message for the muscle to relax and lengthen

Question 7

What is the method of PNF?

Answer 7

The target muscles are stretched to the limit (the full range of movement).
The stretched position is held for a few seconds – with the help of a partner. (passive)
The muscle group contracts isometrically (not moving).
The muscles then relax.
The target muscles are stretched again – but a bit further.
You should try to remember: CRAC (contract/relax/antagonist/contract).

Question 8

What is the physiology behind PNF?

Answer 8

When the stretch occurs, the muscle spindles detect changes in muscle (fibres):
This causes the stretch reflex to be activated, but…
Although a stretch reflex is designed to prevent overstretching…
The aim of PNF is to override the stretch reflex so it does not occur because…
The Golgi Tendon organs (GTOs) are activated, which detect the tension in the muscles.
They then cause the muscles to relax, i.e. the stretch reflex does not occur. This is called autogenic inhibition.
In turn, this allows a greater range of movement than the initial stretch (greater range of movement in the training session).