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Biomechanical Analysis

Biomechanical Analysis. Kinematics – Descriptive analysis of mechanical component without regard to nature of forces causing motion Deals with position, displacement (distance), velocity, acceleration EXAMPLES: Angular velocity at a joint Following the path of a baseball

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Biomechanical Analysis

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  1. Biomechanical Analysis Kinematics – Descriptive analysis of mechanical component without regard to nature of forces causing motion Deals with position, displacement (distance), velocity, acceleration EXAMPLES: Angular velocity at a joint Following the path of a baseball Optimal release angle for shooting a free throw

  2. Biomechanical Analysis • Kinetics – Causal analysis of motion considering the interactive forces that lead to motion • Deals with force, momentum, torque • EXAMPLES: • Force exerted by a high jumper on the ground during takeoff • Stress on the knee joint during a squat

  3. KINEMATIC TOOLS Observer’s Senses Photocells Film Analysis System Digital Video Cameras HD, High Speed DV Cameras DV motion analysis software Goniometer - joint Q Accelerometer - joint acceleration Computers Anthropometric Measures KINETIC TOOLS Force Plate Tensiometer Wind Tunnel Dynamometer Cybex Machine Biodex -jointtorque Treadmill or Cycle Ergometer Electromyography Computer Tools Involved in Biomechanics

  4. Precision – The exactness of a number (limited by tools). EXAMPLES: 4.682 is more precise than 4.6 1,227 is more precise than 1200 Accuracy – The correctness of a number. A measure of systematic error. Reliability – The tendency of a repeated test or experiment to produce the same results. Applicability – The appropriateness of a measurement. Does it measure what it’s supposed to measure? EXAMPLES: A meter stick wouldn’t be useful to measure weight. ROM exercises for the elbow will not aid in healing from ACL reconstructive surgery. Measurement Terms

  5. Position • The position of an object refers to its location in space and time relative to some baseline value or axis (anatomical, orthoganol, angular). Its location. • Linear Position – Cartesian or orthogonal coordinates • UNITS: • English – inches, feet, yards, miles, etc. • Metric – millimeters, centimeters, meters, kilometers, etc.

  6. Position • The position of an object refers to its location in space and time relative to some baseline value or axis (anatomical, orthoganol, angular). Its location. • Angular Position – Rotary or angular coordinates • Units: degrees, radians

  7. Time Time– the measured period of an action from moment to moment. Movement or motion occurs in space and time Units: Englishmetric sec sec

  8. Mass Mass – The quantity of matter composing a body. Ex. The mass of a person is the same on Earth, moon, Mars, or in space Units: Englishmetric slugs kg 1 slug = 14.59 kg

  9. Motion Analysis Exercise Biomechanics All other variables in biomechanics can be derived from position, time, and/or mass Distance Velocity Acceleration Force Inertia, moment of inertia Torque Momentum Impulse Work/energy Power Mechanical Stress Strain

  10. Center of Gravity (mass) • Center of Gravity (Center of Mass) – The average position of the weight or mass of a body, body segment, or object. • The balance point of that object • Drawn as a “point mass” CG 1/2 mass 1/2 mass

  11. Center of Gravity (mass) • Center of Gravity (Center of Mass). • The balance point of that object CG

  12. Center of Gravity (mass) • Center of Gravity (Center of Mass). • The balance point of that object Donut or wheel CG

  13. Center of Gravity (mass) • Center of Gravity (Center of Mass). • Women usually have a lower CG than men • CG can be changed by moving arms & legs • In some sports trying to maintain a level CG is important • Ex. hurdlers lower their torso when the lead leg is raised over the hurdle

  14. Center of Gravity • Body segments - as a rule of thumb, the CGs for body limbs and segments is located at ~ 45% of the length from the proximal end (see Appendix D) SH 28 cm 12.6 cm ELB

  15. Basic Concepts Related to Kinetics Inertia – Resistance to action or change. (p 63) Force – A push or pull acting on a body. (p 63) Free Body Diagram – A picture of a structure being analyzed including a representation of all of the active forces. (p 64)

  16. Basic Concepts Related to Kinetics • Net Force – The sum of all forces acting in a system. (p 65) • Center of Gravity (Center of Mass) – The average position of the weight or mass of a body or object. (p 65) • Weight – The force produced by gravity acting on an object’s mass. (p 66) • Load – A force or weight acting on a structure. • Pressure – Force distributed over a given area. (p 67)

  17. Basic Concepts Related to Kinetics • Volume – The amount of space occupied by a body or object. (p 67) • Density – The mass per unit volume of a body or object. (p 70) • Torque – A tendency to twist or rotate caused by a force acting in a position that is offset from an objects axis or center of rotation. (p 71) • Impulse – The product of a force acting on an object and the time over which it acts. (p 72)

  18. Tools for Measuring Kinetic Quantities • Electromyography (EMG) – Measures the electrical activity in a muscle or muscles. (p 79) • Surface transducers – Electrodes placed on the surface of the skin to measure the electrical activity. • Fine wire or deep muscle transducers – Electrodes which are actually inserted into the muscle tissue. • Dynamography – The use of force plates and platforms for measuring forces applied during movement, usually walking or running. (p 80)

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