Movement Planning

1
Movement Planning
2

• After 90 grueling minutes of regulation and 30
  minutes of overtime, the score was tied USA 0,
  China 0. The 1999 Womans 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. Chinas 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.

3
(No Transcript)
4
Planning a Response

• Stimulus Response Response
• Identification Selection Programming

Backhand is initiated
Backhand is chosen
The ball is perceived
5
Movement Preparation

• What is so important about getting ready to
  perform a skill?
• What makes preparation
  such a critical part of
  successful performance?

6
Planning a Response

• RT is not constant
• As demands increase, time to prepare increases -
  delay can be detrimental!

7
Planning a Response

• What 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?

8
Task-Related Variables Affecting RT

• Movement Complexity
• Number of Choices
• Movement Accuracy
• Predictability

9
Person-Related Variables Affecting RT

• Alertness
• Practice
• Arousal

10
Movement Complexity
Simple with 1 movement 1 reversal
Simple with 1 movement
Simple
Slower _at_ 208 ms
Slower _at_ 195 ms (sprint start)
Fastest _at_ 150 ms
11
Response Choices - Hicks Law
Reaction Speed Slows
Choices Increase
As the number of decisions increases the ability
to react slows by about 150 ms
12
Hicks Law
600
500
RT in ms
400
300
200
100
1
2
3
4
5
6
Number of Choices
13
Chastains Goal
Goalkeeper has 360 ms from time ball leaves
kickers 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!
14
Effects of Increasing Number of Alternatives
Closed Skill
Open Skill
15
Closed Skill - Putting

• Stimulus contrast
• As contrast RT
• Number of environmental features
• Break
• Speed of surface
• Distance
• Direction
• Practice

16
Open 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
17
RT and Tennis Serve

• Server Distance 60 ft Receiver

18
Tennis Serve
A ball served at 90 mph will reach receiver in
660 ms
20 ft
20 ft
20 ft
220 ms
220 ms
220 ms
19
Hicks Law
Practical examples??
20
Practical Implication?

• Increase repertoire to increase choices for
  opponent
• Reduce uncertainty by systematically organizing
  and prioritizing choices

21
Strategies for Improving RT

• Increasing the size, contrast intensity of the
  stimulus
• Practice under a variety of stimulus conditions
• If possible simplify the movement
• Precue participants on what to expect
• Teach participants to anticipate

22
Anticipation

• Predicting from current information
  into the immediate future
• Event anticipation (what)
• Spatial anticipation (where)
• Temporal anticipation (when)
• The more predictable the
  more accurate response

23
Teaching Athletes to Anticipate

• Practice in varied situations so better know
  what, where when an event will happen
• Detect precues for particular responses
• Prepare for most likely events
• On the flip side
• Athletes must vary strategy
• Avoid signaling movements

24
Practical 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

25
The 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

26
The Fake
Stimulus 1 (Fake)
Response 1 (Respond to Fake)
Response 2 (Response to actual move)
Stimulus 2 (Actual move)
Delay
27
Stimulus-Response Compatibility

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

28
Accuracy Movement

• Fitts Law
• Speed accuracy trade-off

3 factors influence accuracy Distance Movement
Speed Accuracy Requirement
29
Distance
A
B
Increased distance increased movement time
30
Target Size
A
B
Smaller targets increased movement time or
decreased accuracy
31
Improving Accuracy in Skills
Distance move closer to net choke down on
racket short handle racquet Target Size larger
ball larger racket face increase
boundaries Increase time to Respond ball speed
32
Improving Accuracy in Skills
Distance move closer to hole choke down on
putter Target size larger ball increase size
of hole
33
Improving Accuracy in Skills

• Should we teach speed or accuracy first?

34
Reducing 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