Movement PlanningMovement Planning

After 90 grueling minutes of regulation and 30 minutes of overtime, the score was tied: USA 0, China 0. The 1999 Woman’s Soccer World Cup would be decided by penalty kicks. China shot first, they were up by 1. U.S. captain Overbek answered back. Next, China and the U.S. were equally successful, tying it up at 2-2. This brought up Ying. As her kick shot towards the left side of the goal, the U.S. goalkeeper, Briana Scurry, dove with outstretched arms, making an amazing save that sent the record crowd of 90,000 into a frenzy. The U.S. then went ahead 3-2 with the next kick. China’s Zhang beat scurry with the 4th penalty shot while Mia Hamm answered, putting the U.S. ahead once again. The final kicker for China put her shot far left of Scurry, tying the game at 4-4. The hopes of the U.S. team rested on the 5th and final kicker, Brandi Chastain. The packed stadium was silent as they watched her approach the ball. She drilled it off her left foot. The Chinese goalkeeper responded but she was too late. The ball soared past her, and history was made: USA 5, China 4.

Planning a ResponsePlanning a Response

Stimulus Response ResponseIdentification Selection

Programming

The ball is perceived

Backhand is chosen

Backhand is initiated

Movement PreparationMovement Preparation

What is so important about getting ready to perform a skill?

What makes preparation such a critical part of successful performance?

Planning a ResponsePlanning a Response

RT is not constantAs demands increase, time to prepare

increases - delay can be detrimental!

Planning a ResponsePlanning a ResponseWhat factors influence how long it takes to

prepare an action or how well this is done?If a person is prepared, how long can the

person maintain this readiness?

Task-Related Variables Task-Related Variables Affecting RTAffecting RT

Movement ComplexityNumber of ChoicesMovement AccuracyPredictability

Person-Related Variables Person-Related Variables Affecting RTAffecting RT

AlertnessPracticeArousal

Movement ComplexityMovement Complexity

SimpleSimple with 1 movement

Simple with 1 movement & 1 reversal

Fastest @ 150 ms

Slower @ 195 ms (sprint start)

Slower @ 208 ms

Response Choices - Response Choices - Hick’s LawHick’s Law

ChoicesIncrease

ReactionSpeed Slows

As the number of decisions increases the ability to react slows by about 150 ms

Hick’s LawHick’s Law

400

500

100

600

200300R

T in

ms

1 2 3 4 5 6

Number of Choices

Chastain’s GoalChastain’s GoalGoalkeeper has 360 ms from time ball leaves kicker’s foot to decide on response & execute movement (RT & MT) before ball crosses goal

Assuming has only 2 response choices, RT about 300 ms

Leaves only 60 ms to execute response!

Effects of Increasing Number Effects of Increasing Number of Alternativesof Alternatives

Closed Skill Open Skill

Closed Skill - PuttingClosed Skill - Putting Stimulus contrast

– As contrast RT Number of

environmental features– Break– Speed of surface– Distance– Direction

Practice

Open Skill - Tennis ServeOpen Skill - Tennis Serve

Flat serve Directly at receiver

Served to outside corner

Effects of increasing number of serves

Fast Ball Directly at receiver

Served to outside corner

Slice serve Served to inside corner

Served to outside corner

RT and Tennis ServeRT and Tennis Serve

ServerServer Distance = 60 ftDistance = 60 ft ReceiverReceiver

Tennis ServeTennis ServeA ball served at 90 mph will reach receiver in 660 ms

20 ft 20 ft20 ft

220 ms 220 ms 220 ms

Hick’s LawHick’s Law

Practical examples??

Practical Implication?Practical Implication?

Increase repertoire to increase choices for opponent

Reduce uncertainty by systematically organizing and prioritizing choices

Strategies for Improving RTStrategies for Improving RT

Increasing the size, contrast & intensity of the stimulus

Practice under a variety of stimulus conditions

If possible simplify the movementPrecue participants on what to expectTeach participants to anticipate

AnticipationAnticipation Predicting from current information

into the immediate future

– Event anticipation (what)– Spatial anticipation (where)– Temporal anticipation (when)

The more predictable the more accurate response

Teaching Athletes to Teaching Athletes to AnticipateAnticipate

Practice in varied situations so better know what, where & when an event will happen

Detect precues for particular responses Prepare for most likely eventsOn the flip side…• Athletes must vary strategy Avoid signaling movements

Practical ApplicationsPractical Applications

Practice to recognize cues & tendencies Prepare learner to respond

– Warning signal like “set” command– Toss of ball in serve

Vary foreperiod or warning signal– Interval time should range from 1 - 4 seconds for

prediction and precision– Randomize foreperiod length to decrease anticipation

The FakeThe Fake RT slower for second response then

for first response

Successful fake– Must be realistic– Timing is critical

Comes with practice

Practice allows reading fakes better

The FakeThe FakeStimulus 1(Fake)

Response 1(Respond to Fake)

Stimulus 2(Actual move)

Delay

Response 2

(Response to actual move)

Stimulus-Response Stimulus-Response CompatibilityCompatibility

Extent to which stimulus & response naturally related– If low - increased preparation time– If high - decreased preparation time

Accuracy & MovementAccuracy & Movement

Fitts LawSpeed accuracy trade-off

3 factors influence accuracyDistanceMovement SpeedAccuracy Requirement

DistanceDistance

A

B

Increased distance = increased movement time

Target SizeTarget Size

A

B

Smaller targets = increased movement time or decreased accuracy

Improving Accuracy in SkillsImproving Accuracy in Skills

Distancemove closer to netchoke down on racketshort handle racquet

Target Sizelarger balllarger racket faceincrease boundaries

Increase time to Respondball speed

Improving Accuracy in SkillsImproving Accuracy in Skills

Distance

move closer to hole

choke down on putter

Target size

larger ball

increase size of hole

Improving Accuracy in SkillsImproving Accuracy in Skills

Should we teach speed or accuracy first?

Reducing Response TimeReducing Response Time

Reducing Movement Time– Increase speed of movement– Reduce length of movement

Self-defense no back arm movement Hockey shot in front of net no backswing

– Increase distance between performer and opponent

Receiving serve behind baseline