1 / 14

Chapter 13: Equilibrium and Human Movement

Chapter 13: Equilibrium and Human Movement. Basic Biomechanics, 4 th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University. Objectives. Define torque, quantify resultant torques, and identify the factors that affect resultant joint torques

london
Télécharger la présentation

Chapter 13: Equilibrium and Human Movement

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 13: Equilibrium andHuman Movement Basic Biomechanics, 4th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University

  2. Objectives • Define torque, quantify resultant torques, and identify the factors that affect resultant joint torques • Identify the mechanical advantages associated with the different classes of levers and explain the concept of leverage within the human body • Solve basic quantitative problems using the equations of static equilibrium • Define center of gravity and explain the significance of center of gravity location in the human body • Explain how mechanical factors affect the body/s stability

  3. EquilibriumTorque Torque: • T = Fd Moment arm: • In the body, moment arm of muscle is the perpendicular distance between muscle's line pull and joint center • Largest moment arm at an angle of pull ~900 • Vector quantity, magnitude and direction • Fd & counterclockwise (+) & clockwise (-)

  4. Resultant Joint Torques • Product of muscle tension and muscle moment arm produces a torque at the joint crossed by the muscle • Agonist and antagonist muscle groups • Net joint torque • Concentric and eccentric • Two joint muscles • Factors that affect net joint torques • Speed’s affect on net joint torques

  5. Levers Lever: Fulcrum: First class lever: Second class lever: Third class level: Most levers within the body are third class

  6. Lever Systems • Moment arm of applied force > moment arm of resistance • Resistance arm is longer than force arm Mechanical advantage = Moment arm (force) Moment arm (resistance)

  7. Anatomical Levers • In the human body, most lever systems are third class • Arrangement promotes • Range of motion • Angular speed • Forces generated must be in excess of the resistance force • Two components of muscular force • rotary and parallel component

  8. Equations of Static Equilibrium Equilibrium: • Three conditions for equilibrium: 1. Fv = 0 2. Fh = 0 3. T = 0

  9. Equations of Dynamic Equilibrium Dynamic equilibrium: • Fx - māx = 0 • Fy - māy = 0 • TG - ī = 0

  10. Center of Gravity (CG)Center of Mass Center of Mass / Center of Gravity: • The CG of a symmetrical object of homogeneous density, is the exact center of the object • When mass in is not constant, CG shifts in the direction of greater mass.

  11. Locating the Center of Gravity • For one-segment, balance point in three different planes • As projectile, the body’s CG follows a parabolic trajectory • Weight vector acts as the CG

  12. Locating the Human BodyCenter of Gravity Reaction board: • requires a scale, a platform & rigid board with sharp supports on either end. Segmental method: • uses data for average locations of individual body segments CGs as related to a percentage of segment length

  13. Stability and Balance Stability: • Factors that affect: • Mass, friction, center of gravity & base of support Balance: • Foot position affects standing balance

  14. Summary • A muscle develops tension and produces torque at the joint that it crosses. • Muscle and bones function as levers. • The angle of muscle pull on a bone produces rotary and parallel components of force • When a body is motionless, it is in static equilibrium. • The behavior of a body is greatly influenced by location of center of gravity. • Stability is resistance to disruption og equilibrium

More Related