Observing and Analyzing Performance (1)

1. Observing and Analyzing Performance (1) • The Nature of Skills • Movement patterns - a general series of movements having common elements. Ex: running, jumping, walking, throwing, striking, pushing • Skill - adaptation of general movement pattern to constraints of a particular task. Ex: high jump, baseball hitting, softball pitching • Technique - a particular type of the same skill. Ex: power hitter, contact hitter • Style - individual adaptations of a technique. Ex: short backswing, no stride • Constraints - limitations associated with the event. Ex: rules, equipment, environment, limitations of performer.

2. Observing Performance (2) • Classification of Skills According to type of environment: • Open - unpredictable environment. Ex. baseball hitting, jump shot • Closed - predictable environment. Ex: free throw, golf shot, high jump • Classification according to how it is done • Discrete - definite beginning and ending. Ex: jump shot, shot put, high jump • Repeated discrete - assembly line, tennis forehand. (Subject to repetitive motion disorders) • Continuous - no definite beginning and ending. Ex: running, walking, work tasks

3. Oberving performance (3) • Observing Skill Performances • Discrete skills - divide into phases such as (1) preparation, (2) execution, (3) follow-through/recovery • Continuous/cyclic - select one cycle and divide it into phases. Ex: support, swing phases in walking • The analysis (holistic model) • Identify overall performance objective (OPO) –(Table next slide) • When two or more objectives are identified, priority must be set (e.g., speed vs accuracy • Divide skill into discrete parts. Ex. Stance, stride, swing, follow-through • Identify the mechanical purpose (MP) of each discrete part • List the biomechanical factors and principles. Ex:: momentum conservation • List the critical features of each part - movements that must be performed for successful execution of the skill (keys to focus on, e.g., knee extended at impact) • Example – article on baseball hitting

5. Analysis Models – the Why? • Holistic – same as Kreighbaum, Adrian p. 18-19 • Read literature and use prior experience to figure out what to focus on (ex: handout on baseball hitting) • Factors-results – Adrian p. 17-18 • Analytical, heirarchial, deterministic • Only useful for goal-oriented skills • Example – article by Hay

6. Analysis Methods • Qualitative vs quantitative • Types and precision of data needed, not the tool available, dictates selection of tool • Naked-eye observational procedures • Observational plan necessary to be consistent and reliable • View multiple times • View from multiple perspectives • Focus on parts, then whole, then parts • Form a visual-mental image of the performance • Use a checklist – borrow or construct your own

7. Constructing Analysis Checklists • Procedures • Study other checklists. Refer to specific sports/skills chapters in textbooks • Read literature to determine what factors are important • List the determinants of skilled and unskilled actions • Arrange checklist in a scale (dichotomous, continuum) • Common factors usually included in checklists • Location of COM relative to base of support • Width of base of support • Range and path of movement of various body segments • Sequencing of segment movements • Projection angleof objects released or struck & total body COM • Overall perception of movement’s effectiveness, smoothness, etc.

8. Videographic and Cinematographic Analyses • Qualitative procedures • Contourograms • Point plots • Stick figures • Quantitative analysis -the process (APAS handout) • Videotaping • Frame grabbing – converting images to digital form • Digitizing – locating segment endpoints in space and time • Calculations done by computer • Applying the multiplier or converting coordinates to life size • Smoothing coordinates • Calculating parameters for each segment and body COM • Linear displacement, velocity, acceleration and inverse dynamics • Angular displacement, velocity, acceleration and inverse dynamics • Displaying output (Digital as well as graphic)

9. Other Analysis Procedures • Optoelectric imaging • Active or passive markers • Dynamographic analysis • F orce platforms, load beams, strain gauges • Accelerometric analysis • Vibrations, impacts, rapidly changing motions • Electrogoniometric analysis • Joint and segment angles • Electromyography • When and to what degree is a muscle active? • Fatigue estimate

14. Begin swing: 183 ms PC

15. Peak 41 ms PC Begin Swing 233ms PC Horiz Pk 38 ms PC

16. Beg Sw - 233 ms PC O0 is horiz & back - 21 ms PC

17. Approximate position when peak bending and Peak torque occurs ~ 40 ms PC