Lecture 2 Biomechanics of Movement

Question 1

What is biomechanics?

Answer 1

• integrative discipline that applies the principles of mechanics to living organisms

Question 2

Biomechanical principles are used for what?

Answer 2

• They are used to understand normal and pathological motion, physical performance, and MOI, with respect to the human body.

Question 3

Definition of Kinematics

Answer 3

• Study of Movement

Question 4

list the types of motion

Answer 4

• Translational (gliding)
• Rotary (rotational)
• Curvilinear (combination;knee flexion/ext)

Question 5

3 Planes of Motion?

Answer 5

• Sagittal Plane
• Frontal Plane
• Transverse plane

Question 6

Direction of motion (typical joint motion) ?

Answer 6

• Flexion/extension
• Abduction/adduction
• Medial rotation/lateral rotation

Question 7

Quantity of Motion ?

Answer 7

• Translational: meters (m)
• rotary: degrees-
• velocity: linear, angular (deg/sec)

Question 8

Methods to Evaluate Motion (reliability vs validity)

Answer 8

• Visual (observational)
• 2D video video
• 3D motion capture

reliability - how reputable something is

Question 9

what is kinetics

Answer 9

• branch of mechanics dealing with the analysis of forces

Question 10

definition of force?

Answer 10

• A physical quantity that can cause a change in position or alter the direction or speed of rotation of an object

F= ma

Question 11

F=ma is expressed in?

Answer 11

Newtons ( kf x 9.8 m/s2)

Question 12

Newton’s 3rd law

Answer 12

• for every action (force) there is always an equal and opposite reaction

Question 13

joint reaction force?

Answer 13

• the force equal and opposite to one bone acting on another (tibia and femur)

Question 14

Ground reaction force?

Answer 14

• the force equal and opposite to the force acting on the ground.

Question 15

3 parts of ground reaction force vector?

Answer 15

• point of origin
• magnitude
• direction

Question 16

Methods to evaluate joint reaction forces during movement: Biomechanical Modeling

Answer 16

joint reaction forces- are not something we can see

• we have to estimate compressive forces based on math and estimation.

Question 17

Methods to evaluate ground reaction forces during movement: Force plates or platforms

Answer 17

• 3 principal forces:
  downward (vertical)
  medial/lateral
  anterior/posterior

Question 18

What is ground reaction force vector

Answer 18

Vector sum of the 3 principle components

Question 19

the 3 qualities of GRF

Answer 19

• magnitude
• point of origin (center of pressure)
• Direction (towards center of mass)

Question 20

Force vs Pressure, what is force?

Answer 20

Force: a physical quantity that can cause a change in position or alter the direction or speed of rotation of an object (F=ma)

Question 21

Force vs Pressure, what is pressure?

Answer 21

Pressure: a physical quantity that is a force spread over a given area (P=Force/Area)

Question 22

Center of Pressure?

Answer 22

• the location of the average weight bearing force (ie origin of the GRF vector)
• influenced by movement of the center of mass of the body
• commonly used as an indicator of postural stability

Question 23

Balance & COP excursion

Answer 23

• the more spread CoP the more unbalanced

- the tighter the spread the better the balance

Question 24

Torque/Moment

Answer 24

• Force that causes rotation about an axis

- Torque = Force x Lever arm

Question 25

Internal vs External Joint Torque?

Answer 25

• External Torque: rotational potential of forces outside of the body acting on a joint.
• Ground reaction force
• Gravity

Question 26

Internal Joint Torque?

Answer 26

• Rotational potential of forces acting within the body acting on a joint.
• muscle forces