Lecture 2 Biomechanics of Movement Flashcards
What is biomechanics?
- integrative discipline that applies the principles of mechanics to living organisms
Biomechanical principles are used for what?
- They are used to understand normal and pathological motion, physical performance, and MOI, with respect to the human body.
Definition of Kinematics
- Study of Movement
list the types of motion
- Translational (gliding)
- Rotary (rotational)
- Curvilinear (combination;knee flexion/ext)
3 Planes of Motion?
- Sagittal Plane
- Frontal Plane
- Transverse plane
Direction of motion (typical joint motion) ?
- Flexion/extension
- Abduction/adduction
- Medial rotation/lateral rotation
Quantity of Motion ?
- Translational: meters (m)
- rotary: degrees-
- velocity: linear, angular (deg/sec)
Methods to Evaluate Motion (reliability vs validity)
- Visual (observational)
- 2D video video
- 3D motion capture
reliability - how reputable something is
what is kinetics
- branch of mechanics dealing with the analysis of forces
definition of force?
- A physical quantity that can cause a change in position or alter the direction or speed of rotation of an object
F= ma
F=ma is expressed in?
Newtons ( kf x 9.8 m/s2)
Newton’s 3rd law
- for every action (force) there is always an equal and opposite reaction
joint reaction force?
- the force equal and opposite to one bone acting on another (tibia and femur)
Ground reaction force?
- the force equal and opposite to the force acting on the ground.
3 parts of ground reaction force vector?
- point of origin
- magnitude
- direction
Methods to evaluate joint reaction forces during movement: Biomechanical Modeling
joint reaction forces- are not something we can see
- we have to estimate compressive forces based on math and estimation.
Methods to evaluate ground reaction forces during movement: Force plates or platforms
- 3 principal forces:
downward (vertical)
medial/lateral
anterior/posterior
What is ground reaction force vector
Vector sum of the 3 principle components
the 3 qualities of GRF
- magnitude
- point of origin (center of pressure)
- Direction (towards center of mass)
Force vs Pressure, what is force?
Force: a physical quantity that can cause a change in position or alter the direction or speed of rotation of an object (F=ma)
Force vs Pressure, what is pressure?
Pressure: a physical quantity that is a force spread over a given area (P=Force/Area)
Center of Pressure?
- 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
Balance & COP excursion
- the more spread CoP the more unbalanced
- the tighter the spread the better the balance
Torque/Moment
- Force that causes rotation about an axis
- Torque = Force x Lever arm
Internal vs External Joint Torque?
- External Torque: rotational potential of forces outside of the body acting on a joint.
- Ground reaction force
- Gravity
Internal Joint Torque?
- Rotational potential of forces acting within the body acting on a joint.
- muscle forces
