Repetitive Strain Injury

Question 1

Repetitive Strain Injury

Answer 1

Neuromuscular disorder in hand, wrist, arm, neck and or shoulder due to excessive and repititive motion.
–> Carpal Tunnel Syndrome
–> Tennis Arm
–> Tendonitis

Question 2

Tennis Arm

Answer 2

A non-bacterial tendonitis at the elbow

Question 3

What % of Dutch people have an RSI related symptom?

Answer 3

30%

Question 4

What % of cases have their symptoms remained over the weekend?

Answer 4

24%

Question 5

How many people experience limitations in functioning due to RSI?

Answer 5

15%

Question 6

What are the three stages of RSI?

Answer 6

Minor Complaints
–> Clear relation between work and pain.
–> During the weekend the pain subsides
–> Feelings of cramp or prickling sensations in the limb
Serious Complaints
–> Pain remains in the evening and night
–> Pain extends to neighboring joints
–> Reduced potential to generate force
Very Serious Complaints
–> Always painful! (chronic)
–> Pain feels like numbness, clearly a prickling sensation
–> Painful spots feel cold or warm

Question 7

What are the three causes of RSI?

Answer 7

Dynamiche RSI / Repetitive Motion
–> Too many arms, wrist, and finger motion
–> Hairdressers, musicians
Static RSI / Too little motion
–> Forced, constant posture
–> Too few rest periods
–> Computer Work

Often RSI occurs due to the combination!!!!

Question 8

Small motor units can

Answer 8

Go a very long time without being fatigued
–> Eye muscles might have ten fibres in each unit

Question 9

Large Motor Units

Answer 9

Get fatigued very quickly in order to create very large forces
–Thigh muscles can have a thousand fibres in each unit

Question 10

What is Henneman’s Size Principle?

Answer 10

Motor units are generally recruited in order of smallest to largest (fewest fibres to most fibres) as contraction increases

Question 11

Cinderella Hypothesis

Answer 11

Stress causes long-term, non-effective muscle contraction, also during non-motion

–> Stress acts as the bad sisters of Cinderella, it prevents the muscles and tendons to recuperate and relax

–>The Cinderella hypothesis proposes that the development of chronic muscular pain is due to an overuse of fibers belonging to low-threshold motor units.

Question 12

What is the physiological explanation for RSI?

Answer 12

The muscles are constantly slightly contracted
–> Subobtimal blood flow to the area
–> Oxygen is supplied inefficiently
–> Metabolic waste piles up
–> Micor damage to muscle tissue yields pain
–> Natural Reaction to pain is increased muscle tension

Question 13

What is co-contraction or stiffness?

Answer 13

It is simultaneous contraction of opposing muscle groups?
–> It is to maintain balance
–> Muscle tension
–> To be precise
–> To reduce the effects of neuromotor noise

Question 14

Learning to ski entails ______ and ______ degrees of freedom.

Answer 14

Freezing and freeing degrees of freedom
When you first start skiing you probably freeze up and co-contract your muscles to maintain balance
But to get better you need to relax the tension and free up your degrees of freedom

Question 15

Jerk

Answer 15

Is the rate of change for acceleration
–> When low jerk people move smoothly

Question 16

Muscle Stress Change

Answer 16

Is contracting muscles etc

Question 17

How do we optimise movement?

Answer 17

We try to move with minimum energy use and in the most smooth, efficient way to not cause muscle stress or injury
–> No jerk, torque change, muscle stress change etc
–> This leads to minimization of variability in motor variance

Question 18

Neuromotor-noise theory

Answer 18

Neural signals are inherently noisy
People try to accommodate for the negative consequences of noisy efferent signals through
–> Co-contraction which increases the stiffness of the effector system
–> Which enhances the predictability of the system
–> Slightly increasing co-contraction is good but too much you will tremor again

Question 19

What are the two types of co-contraction?

Answer 19

Phasic, is motion-based and changes the muscle length.
Are only used when needed (biceps)

Tonic/postural which is isometric and there is no muscle-length change
Help us to maintain balance for example
(Effector system remains stationary)

Question 20

What is an error in psychology

Answer 20

The mismatch between intention and behavioural outcome

Question 21

In an experiment external stressors such as _______ increased _______ during ________

Answer 21

White noise increased co-contraction during deacceleration