(S1W7) Human Movement Variability part 2

Question 1

Do we want execution and outcome variability to be high or low? traditional approach

Answer 1

• We want outcome variability to be low
• Consistent movement pattern –> consistent outcome, so low execution variability is good
• E.g. cricket bowling - if you want the ball to land in the same place every time you want their run up and throw to be the same every time
• Motor learning involves reduction of variability

Question 2

(Fleisig et al, 2009) baseball pitcher study

Answer 2

• Studied baseball pitchers of all levels
• Found 11 kinematic parameters
• Found greatest variability in youth baseball pitchers and as players got more skilled, variability decreases

Question 3

variability as noise

Answer 3

• There’s an optimal movement that has some noise added on top that is the actual movement they do
• we want to reduce that noise as much as possible to get their optimal consistent movement.

Question 4

sources of noise

Answer 4

• Motor commands (centrally) - brain and spinal cord
• Sensorimotor systems (periphery) - motor units

Question 5

(van Beers et al, 2004) study

Answer 5

• Study tried to separate different sources of variability to see which one actually causes the variability we see in real life
• removed all sources of error except execution error
• simulated the movement on computer and added 3 different types of error
• signal-dependent
• signal-independent
• temporal
• found all 3 of these combined produces same results as human participants real life results

Question 6

perspectives on movement variability

Answer 6

• Traditional - variation is noise (unwanted)
• Dynamical systems - there are different combinations of movement that can be successful - variation has functional role
  ○ Adapt to external variables (e.g. weather, fatigue)
  ○ Covariation
  ○ Feedback corrections
  ○ Reduce loading during repetitive activates
  ○ ‘the bliss of motor abundance’ (Latash, 2012)