Lecture 11c, Principles of Speed & Accuracy (Force) Flashcards
Force Variability
as force increases, variability in forces also increases (up to a point - ~70% of max)
- force variability only increases up to a certain point in our maximum force (peaks at 65-70% and will decrease afterwards)
With the exception of very fast (near max forces) movement positional variability (We) increases linearly with force/MT
“muscular forces produce movements & variability in muscular forces produces variability in movements”
- need to translate mean movement time to percentage of maximum force
- if you are moving very fast, you would have to apply quite a lot of force - essentially fast movement time means high % of max force applied
- when movement time is slow it means you did not apply much of your maximum force
- maximum force high on left and low on right end of graph
- variability of our movement tends to increase as we apply more force but as some point variability will begin to decrease
Scaling force parameter (of football throw) for distance
when we want a certain outcome we will have to adjust our parameters for the motor program
- when we want to throw a football to 10m based on our GMP and schema we may apply a parameter of A which is smaller than parameter of B for an outcome to 30m
- even though we have never thrown a football to 20m we can use a schema to apply C to our force parameter
- since we apply twice the force for 20m compared to 10m we should see twice the variability in our force parameter assigned to 20m compared to 10m - should be greater execution error or effective target width to the 20m (less accurate throwing to 20m than to 10m)
In the slower Fitt’s type tasks, we optimize/balance size of initial forces & feedback corrections
- this is known as hybrid control where we combine both open and closed loop processes
goal: bring the limb to target in efficient way (i.e. shortest time without overshooting)
how? trade-off speed for accuracy by optimizing duration of both the primary force (impulse) and corrective movements (amount of time spent in corrective movements)
primary force/impulse: open-loop
- initial ballistic programmed impulse…intentionally short
corrective submovement(s): closed-Loop
- visual feedback can be used to “home-in” on final target