Exam 1 Lectures

• Kinesiology/Pathomechanics

  The study of human movement and the mechanical factors that influence it
• Kinematics

  the subfield of biomechanics that describes the motion of objects without considering the forces that cause the motion. Two types of motion: Translation (linear motion of rigid body where all parts move parallel and in the same direction) and Rotation (circular path around pivot point where all points rotate in same direction thru same degrees)
• Kinematics—Examples

  • A body translates forward, An elbow rotates around an axis
• Osteokinematics

  Motion of bones in 3 cardinal planes: Sagittal (mid- or off center; L/R; flex/ext), Frontal (also called coronal; front/back; abd/add), Horizontal (also called transverse; top/bottom; rotation/supination/pronation)
• OKC vs CKC

  Open Kinetic Chain: not fixed to earth or immovable object, isolates movement; Closed Kinetic Chain: fixed to earth or immovable object, a distal segment of a kinematic chain fixed to an immovable object
• Arthrokinematics

  • Roll, Slide (glide), Spin; the small movements that occur within the joint surfaces. These movements are essential for normal joint function.
• Close-Packed vs Loose-Packed Positions

  Close Packed: Good congruency, Taut ligaments, Increased stability, Little accessory motion. Associated with habitual positions, i.e., standing at full knee extension. LOOSE PACKED: Decreased congruency, Loose ligaments, Accessory motion is max-position of mobilization
• Kinetics and Biomechanics

  Study of motion under the action of forces: Vectors!
• Load/Stress

  Every tissue in the body can have these forces/loads applied, causing stresses and strains on that tissue.
• Viscoelasticity

  Viscous + Elastic, a measure of a material’s time-dependent strain; another way to say it:change in stiffness as a function of time (faster loading = increased stiffness); increased load rate instantaneously more brittle
• Creep and Stress Relaxation

  Creep: Constant stress, Deformation over time (strain). Stress relaxation: Constant position (strain), Change in stress over time
• Moments (Torques)

  Torque = force that induces rotation: Torque = MA x force, Moment arm (MA): perpendicular distance from axis to point of force application, Static linear equilibrium if all forces = net zero
• No torque if the force:

  Pierces the axis of rotation, Parallels the axis of rotation
• Torque example at the hip

  • Which muscles can create torque for rotation (IR/ER) of the hip? Why?
• Balance of Torque

  Concentric: Int Torque > Ext Torque, Eccentric: Ext Torque > Int Torque, Isometric: Ext Torque = Int Torque, All muscle action cause a JRF
• Muscle/Joint Interaction: Force Couples

  Opposing linear pulls of force that result in same rotary motion; Advantages: efficient torque production, controlled rotation, stability

  Examples: hip joint- hip flexors and glut. Max., ankle joint: ant. Tibialis and gastric/soleus complex
• Muscle/Joint Interaction: Levers

  Components: Rigid body (bone), forces (internal/external), point of rotation (axis), Lever: converts linear force into rotary torque (T = MA x F)
• Mechanical Advantage (ma)

  mechanical advantage is ONLY dependent on the moment arms of the two forces

  Internal force MA/ external force MA= ma, 2nd class: mech. adv. > 1, 3rd class: mech. adv. < 1
• axis

  point where everything rotates around
• degrees of freedom

  # of planes
• accessory motions

  arthokinematics, joint play
• osteokinematic motions

  voluntary
• open kinetic chain


  isolates movement
• arthorkinematics

  describe what happens btwn 2 joint surfaces
• roll

  multiple points on one surface contact multiple points on the other
• spin

  single point on one surface articulates with (rotates on) a single point on the other
• slide

  single point on one surface contacts multiple points on the other
• concave moving on a fixed convex

  roll and glide same direction; axis is within the fixed convex bone; OKC;
• convex moving on a fixed concave

  roll and glide in opposite directions; axis is within the moving convex bone; CKC
• convex moving on fixed concave

  closed chain
• concave moving on fixed convex

  open chain
• loose packed

  open packed, increased ROM
• vectors

  length determines magnitude; Longer arrows = higher magnitude; Direction of arrow = direction of force
• stiffness

  more resistance under load
• ductility

  less resistance under load
• elastic region

  stretch and go back to original
• Young's Modulus

  ratio of stress to deformation (strain) (Y/X)--measure of tissue stiffness or elasticity
• slow viscosity

  ductile
• fast viscosity

  stiff
• viscoelasticity

  measure of a material’s time-dependent strain; another way to say it:  change in stiffness as a function of time (faster loading = increased stiffness)