(S1W7) Human Movement Variability part 1 Flashcards
define motor skill
“The ability to bring about some end result with maximum certainty and minimum outlay of energy” (Schmidt)
human movement variability (Nikolai Bernstein, 1930)
- He observed blacksmiths using a hammer
- He observed that these skilled blacksmiths were able to hit the hammer on the nail in the same spot every time but the way they swung the hammer was different every time
- This is the first observation showing we may have variability in the way people move
how do degrees of freedom affect variability
As we increase the degrees of freedom, there are more combinations of different ways to achieve the same goal
kinetic movement variations
- Motor system noise
- Planning errors/differences
- Feedback corrections
- Abundance, redundancy, covariation
○ Abundance = multiple different ways of doing something
○ Redundancy = more variables than we actually need - e.g. can shoot at the target only moving shoulder, don’t need to move elbow and wrist as well
○ Abundancy leads to redundancy
Covariation refers to varying things in coordination with each other - e.g. the more you extend your elbow, the less you extend your shoulder
2 main types of variability
- Outcome variability = variability in the result
- Execution variability = kinematic variability (the way you achieve the result)
Ball speed in cricket bowling - execution or outcome?
Outcome because it is the outcome of how the bowler moves
Footballer taking a free-kick, the amount of spin they are able to impart on the ball - execution or outcome?
Outcome because the amount of spin on the ball is the outcome of how they kick ball
Angle of boxers elbow when throwing a jab - execution or outcome?
Execution because it is how they are doing something
Duration of golfer’s downswing - execution or outcome?
Execution because it is a measure of their movement
