: Protective response hypothesis

Question 1

Response to threat to tissues

Answer 1

• Activation of noci afferents by mechanical, chemical or thermal stim
• Nervous system generates:
1. Pain response
2. Output to reduce or remove threat
• Therefore tissues become protected
• So “protective response hypothesis” = various motor control responses serving to protect tissue from further pain

Question 2

Protective responses to pain

Answer 2

1. Redistribution of activity within and between muscles
2. Changes in mechanical behaviour- e.g. mod movement or stiffness
3. Protection from nociception or injury- 1+2=3
4. Possible changes at multiple levels of motor system
5. Short term benefits, long term consequences

Question 3

Redistribution of activity

Answer 3

• Different recruitment of muscles

* Gross features of task maintained but quality is reduced

Question 4

Mechanical behaviour changes

Answer 4

• Active units within muscles altered
• Direction of force altered
• Change of joint load

Question 5

Protection

Answer 5

• Redist + mech behave change may unload painful structures

* Sustained altered loading may have long term negative effects

Question 6

ST +, LT -

Answer 6

• ST = Protection of injured/painful area
• LT =
o increased/mod loading
o altered/ «_space;relative motion
o possible decrease in movement variability
• pain provides stim to change movement strategy
• resolution of pain/injury doesn’t necessarily mean return to initial pattern

Question 7

Possible observed protective behaviours

Answer 7

• Increased stiffness to limit movement
• Decreased force amplitude (e.g. limping)
• Change force direction
• Redist muscle activity
• Avoidance of movement (e.g. bed rest)
• Avoidance of participation (e.g. absenteeism)