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Introduction to Biomechanics EXSC 408L - Fall ‘10

Introduction to Biomechanics EXSC 408L - Fall ‘10. Dr. Kathleen E. Sand (BU 2007; USC 2004) Kcosta@usc.edu Email subject line: EXSC 408L … Office Hours (PED B7) TUES 230 - 430PM WED 1145AM - 145PM & by appointment Course Reader:

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Introduction to Biomechanics EXSC 408L - Fall ‘10

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  1. Introduction to BiomechanicsEXSC 408L - Fall ‘10 • Dr. Kathleen E. Sand (BU 2007; USC 2004) • Kcosta@usc.edu • Email subject line: EXSC 408L … Office Hours (PED B7) • TUES 230 - 430PM • WED 1145AM - 145PM • & by appointment • Course Reader: Selections from “Biomechanics of Sport” by D. Miller & R. Nelson • Lab website • http://www.usc.edu/dept/LAS/kinesiology/exsc408l/lab/lab.html

  2. Proposed Semester Schedule Fall 2010

  3. Biomechanics Uses Newton’s Laws to analyze the cause-effect relationships of human movement Clinical– gait, rehab, prosthetics Ergonomic– lifting, repetitive motion tasks, work areas, auto design Sport– performance enhancement, injury diagnosis & prevention, performance prosthetics, implement design (shoes, pads, helmets, clubs, landing mats, bikes, etc.)

  4. Biomechanics Research Entry preparation Loading Tipping Pushing Flight • Using Newtonian mechanics to understand and characterize human motion in order to improve task performance and decrease injury potential. • complex, mulit-joint movements • specific mechanical objectives • well-practiced tasks & highly skilled performers • identify control strategies / parameters • apply to broader populations within varying contexts

  5. Problem-Solving Approach Coach / Athlete / Clinician-Driven Performance or injury-related issue? Assessathlete’s physical capacity (eg. control & coordination) Current state of the system Provide mechanical basis for implementing individualized training / technique modifications Identify mechanics athlete uses to generate and control total body momentum within specific context Individual solution space Identifytechnique that complements athlete’s capacity How are they going to get there? Identify critical factors that improve task performance Mechanical objective

  6. Components of Biomechanics Kinematics Study of spatial and temporal aspects of human movement Linear & Angular position, velocity, acceleration Kinetics Study of forces and torques involved in human movement Linear & Angular forces, torques, impulse, power, work

  7. Kinematics Branch of mechanics involving Motion Analysis, quantifying movement characteristics without considering forces that cause the motion Temporal & Spatial characteristics (i.e. position, velocity, acceleration) Qualitative or Quantitative Linear & Angular Kinetics Branch of mechanics that investigates the forces that cause motion (e.g. ground reaction forces, net joint forces, impulse) More Quantitative than qualitative Linear & Angular Components of Biomechanics

  8. Quantitative vs. Qualitative Analysis Quantitative • Calculating absolute values for variables of interest • …approach velocity of 10m/s Qualitative • Non-numerical descriptive analysis for variables of interest • …increased forward trunk lean during approach

  9. Quantitative Analysis -Video & review - Motion Analysis Software - Force Plates - Power Rack - Electromyography (EMG) - Computer Modeling Qualitative Analysis - Video & review - Motion Analysis Software Biomechanical Tools

  10. Quantitative Filming (2D) Stationary Camera (3D)  2 cameras View perpendicular to plane of motion Calibration object of known length Know the playback rate of your camera, VCR and/or computer video card (standard 30 fps) Step rate, step length, joint & segment angles, velocities Qualitative Filming Desired field of view for motion of interest Understand analysis limitations (parallax) and strengths (setup time, overall picture) Body & segment orientation in space or relative to equipment, general technique description Videography

  11. Planes & Axes of Motion

  12. Planes of Motion Frontal Plane stationary Sagittal Plane stationary

  13. Observable Joint Motion Frontal Plane stationary Sagittal Plane stationary Trunk Lateral Flexion Pelvis Time 1 Time 2 Hip Adduction Hip extension Knee extension Pronation Supination

  14. Sport Biomechanics Investigate the influence of technique on … • Force generation (ground reaction & muscle) • Mechanical loading (across joints) • Injury (potential factors and prevention) • Event performance

  15. How does Biomechanics facilitate performance? • Provides coaches & athletes with the tools to answer questions regarding event technique & performance (i.e. critical zones & critical performance variables or factors) • Uses mechanically-based principles to develop a relationship between • task objectives (mechanical), and • athlete characteristics (e.g. muscular strength, joint range of motion, coordination). In order to identify athlete specific solutions or strategies to achieve event goals.

  16. Applications & Significance • Critical problem-solving skills • Sport - e.g. coaching, sport-science, personal training • Clinical - e.g gait analysis lab, PT, OT, prosthetics • Ergonomic - e.g equipment design (auto), insurance consulting, workplace environment • Corporate / Technology - e.g. forensics, footwear, golf, helmet design, etc. • Education • Technology - 3D motion capture for animation (movies & gaming) • Simulation (modeling) vs. Animation

  17. Linear Kinematics - Variables Position where an object is in space relative to a global coordinate system Displacement change in an object’s position independent of direction Velocity (vector) rate of change in position; V = (p2-p1)/(t2-t1) • Horizontal Velocity; Vh = (x2-x1)/(t2-t1) • Vertical Velocity; Vv = (y2-y1)/(t2-t1) • Resultant Velocity; Vr = √Vh2 + Vv2 Acceleration (vector) Rate of change in velocity; a = (v2-v1)/(t2-t1) Horizontal, Vertical, Resultant Vh Vr Vv

  18. Angular Kinematics Angular Position () Segment Angle angle of a segment relative to a fixed reference (e.g. shank angle relative to right horizontal anchored at the ankle joint) Joint Angle relative angle between two adjacent segments (e.g. upper arm & forearm compose elbow angle)  Elbow  Shank

  19. Angular Kinematics Angular Velocity () rate of change in angular position  = (2-1)/(t2-t1) Angular Acceleration () rate of change in angular velocity  = (2-1)/(t2-t1) Time 2 Time 1 

  20. Newton’s Laws 1st Law:Inertia An object in motion (rest) tends to stay in motion (rest) unless acted upon by an external force. 2nd Law:F = ma The acceleration of an object of constant mass is proportional to the sum of forces acting upon the object’s center of mass. 3rd Law:Conservation of Momentum When a force is applied to an object there is an equal and opposite reaction force. …Practical Applications?

  21. Divisions of Mechanics Statics Study of systems with zero acceleration (a = 0), at rest or in a constant state of motion. F = ma = 0 Dynamics Study of systems in motion, with non-zero acceleration F = ma

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