Performance and Motor Control Characteristics of Functional Skills Chapter 7 Performance and Motor Control Characteristics of Functional Skills Concept: Specific characteristics of the performance of various motor skills provide the basis for much of our understanding of motor control ©2011 McGraw-Hill Higher Education. All rights reserved

©2011 McGraw-Hill Higher Education. Introduction This chapter extends discussion of motor control theory issues in chapters 5 & 6 to: Consider how motor control processes are involved when we perform specific motor skills Provide guidance for practitioners for teaching these skills ©2011 McGraw-Hill Higher Education. All rights reserved

_______________________________ ___________________________________________________________________speed-accuracy trade-off i.e., when speed is emphasized, accuracy is reduced and vice-versa What are some examples of motor skills that require both speed and accuracy? ©2011 McGraw-Hill Higher Education. All rights reserved

Speed-Accuracy Skills: __________________________ _____________________________________________________________________________________________________________________ If we know the spatial dimensions of two variables: _________________________ MT = a + b log2 (2D/W) Also demonstrated that an index of difficulty could be calculated based on this equation: log2 (2D/W) See Fig. 7.1 for examples of different IDs for manual aiming tasks, and predicted MTs Note how same task (i.e., action goal) can have different levels of performance difficulty ©2011 McGraw-Hill Higher Education. All rights reserved

Application of Fitts’ Law to Non-Laboratory Skills Research has demonstrated that Fitts’ Law predicts MT for various non-laboratory motor skills, e.g., Dart throwing Peg-board manipulation task Used in physical rehab assessment and training Reaching and grasping containers of different sizes Moving a cursor on a computer screen ©2011 McGraw-Hill Higher Education. All rights reserved

Speed-Accuracy Skills: Motor Control Processes General agreement that two motor control processes involved in performance of speed-accuracy skills: 1. Open-loop control – At movement initiation _____________________________________________________________________________________ 2. Closed-loop control – At movement termination ©2011 McGraw-Hill Higher Education. All rights reserved

Speed-Accuracy Skills: Role of Vision Relate to Manual Aiming Skills (e.g., putting key in keyhole – see Fig. 7.2) Role of vision depends on movement phase: _____________________– Assess regulatory conditions of environmental context _____________________– Monitor limb displacement and velocity; shift gaze to keyhole at 50% time-to-contact ____________________– Provide spatial-temporal info to correct movement accuracy errors to ensure insertion of key ©2011 McGraw-Hill Higher Education. All rights reserved

_______________________ ________________________________________________________________ Three components ____________________ Movement of the hand to the object The hand taking hold of the object _________________________ The hand carrying out the intended use for the object (e.g. drinking from it, moving it to another location) ©2011 McGraw-Hill Higher Education. All rights reserved

Relationship of Prehension Components Motor control question concerns the ________________________between the transport and grasp components Initial views proposed the independence of the components Recent evidence shows ___________________________________ ©2011 McGraw-Hill Higher Education. All rights reserved

Relationship of Prehension Components, cont’d Example of research demonstrating temporal relationship of reach and grasp Goodale and colleagues (1991, 2005) showed: 1. Object’s size influences: _________________________________________ 2. Regardless of object’s size or distance Max. grip aperture (point of beginning of hand closure for grasp) ____________________________ Other research shows: Relationship of movement kinematics for prehension components exemplify characteristics of a “coordinative structure” ©2011 McGraw-Hill Higher Education. All rights reserved

Role of Vision in Prehension ________________________________ Assesses regulatory conditions Central vision directs hand to object – provides time-to-contact info to initiate grasp Peripheral vision provides hand movement feedback ______________________________ Supplements tactile and proprioceptive feedback to ensure intended use achieved ©2011 McGraw-Hill Higher Education. All rights reserved

Prehension and Fitts’ Law ______________________________________________________________________________________________________ ______________________________ ____________________for grasping containers of different sizes and quantities of liquid Developed by Latash & Jaric (2002) See “A Closer Look,” p. 144 Critical component is % of fullness Ratio of mug size and liquid level ©2011 McGraw-Hill Higher Education. All rights reserved

____________________________ ____________________________________________________________________________ People demonstrate much individual variation in terms of limb segment involvement Person can adapt to various context demands (e.g., write on different surfaces, write large or small) Handwriting motor control demonstrates characteristics of a coordinative structure ©2011 McGraw-Hill Higher Education. All rights reserved

©2011 McGraw-Hill Higher Education. Handwriting, cont’d ___________________________________________________________________ Write on a piece of paper: I like to sit and read books Write the same sentence with your eyes closed How do the similarities and differences with eyes open and closed demonstrate the role vision plays in the control of handwriting? See the experiment by Smyth & Silvers (1987) – Results in Fig. 7.3 ©2011 McGraw-Hill Higher Education. All rights reserved

__________________________________________________________________ Skill may require two arms to move with the same or different spatial and/or temporal characteristics _____________________________ ©2011 McGraw-Hill Higher Education. All rights reserved

Bimanual Coordination Skills, cont’d ____________________________________________________________________ Demonstrates why it is difficult to rub your stomach and pat your head at the same time, or draw a circle with one hand while drawing a straight line with the other hand Research demonstrates temporal and spatial coupling of the two arms when initially performing asymmetric bimanual skill ____________________________________________________________________________ ©2011 McGraw-Hill Higher Education. All rights reserved

__________________________ ________________________________________________________________________________________________ Provide basis for stereotypic rhythmicity of walking and running gait patterns But, proprioceptive feedback from muscle spindles and GTOs also influence gait ©2011 McGraw-Hill Higher Education. All rights reserved

©2011 McGraw-Hill Higher Education. Locomotion, cont’d _______________________________________ Components of a step cycle (discussed in ch.5 in experiment by Shapiro et al.) Rhythmic relationship between arms and legs Pelvis and thorax relationship during walking ________________________________________________________________________________ Allows for assessment of coordination problems of trunk and legs (e.g. Parkinson’s Disease) Another important motor control characteristic of locomotion Head stability Consider why and implications of head stability problems ©2011 McGraw-Hill Higher Education. All rights reserved

©2011 McGraw-Hill Higher Education. Locomotion, cont’d _______________________________ An important motor control characteristic of locomotion (Initially discussed in ch.5) People spontaneously change from walking to running gait (and vice-versa) at critical speed (specific speed varies across people) Why do spontaneous gait transitions occur? Various hypotheses Most popular: Minimize metabolic energy use (i.e., VO2) Some agreement that no one factor responsible ©2011 McGraw-Hill Higher Education. All rights reserved

©2011 McGraw-Hill Higher Education. Locomotion and Vision When we walk or run, vision is important to enable us to contact objects and avoid contact with objects Contacting objects Experiment by Lee et al. (1982) showed long-jumpers use tau as basis for contacting take-off board accurately [See Fig. 7.4] Avoiding contact with objects _________________________________________________________________________________________ Vision provides body-scaled info to determine how to walk through a door, or step on a step ©2011 McGraw-Hill Higher Education. All rights reserved

_________________________________ Three phases __________________________________________ Movement analysis evidence of the three phases – Experiment by Williams & McCrirrie (1988) Figure 7.6 – Illustrates movement characteristics related to % ball flight time Notable finding (not in figure) – Successful ball catchers initiated final hand and finger shaping 80 msec earlier than non-catchers What do you think are the roles of tactile, proprioceptive, and visual information in the stages of catching a moving object ©2011 McGraw-Hill Higher Education. All rights reserved

Catching a Moving Object, cont’d ___________________________________________________________________ Two critical time periods ______________________ _______________________ Between the two critical periods Brief, intermittent visual snapshots sufficient Specific amounts of time not known ©2011 McGraw-Hill Higher Education. All rights reserved

Catching a Moving Object, cont’d Is vision of the hands necessary to catch a moving object? Key factor in answer is amount of experience Inexperienced – Yes Experienced – No Describe how experience with using vision to catch an object influences a person’s capability to rely on proprioceptive feedback to position hands to catch an object ©2011 McGraw-Hill Higher Education. All rights reserved

Striking a Moving Object Ball speed effect Skilled ”strikers” demonstrate similar ”bat” movement time for all ball speeds, change amount of time before initiating bat movement Visual contact with moving ball Skilled ”strikers” do not maintain visual contact with ball throughout ball flight but visually ”jump” from early flight to predicted location in area to strike ball ©2011 McGraw-Hill Higher Education. All rights reserved