Biomechanics Flashcards
Biomechanics
Principles of forces and motion as applied to the structure and funciton of the human body
Static
Factors associated with non moving systems
Dynamics
Factors associated with moving systems
Law of inertia
An object at rest tends to stay at rest, and an object in motion tends to stay in motion
- force is needed to move, stop, or change the direction of an object
Law of acceleration
Amount of acceleration depends on the strength of the force applied to an object
- the change in an object’s direction depends on the force applied
- acceleration is inversely proportional to the mass of the object
Law of motion
For every action, there is an equal and opposite reaction
Force
Any influence that results in the movement of an object
- point of application
- vector
Vector
A quantity that describes magnitude and direction
Internal force
Muscle, ligamentos restraint, bony support
External force
Gravity, weight, friction
Linear force
Two or more forces activing along the same line
Parallel forces
Occur in the same plane and in the same or opposite direction
Concurrent forces
Two or more forces applied to the same point but pulling in different directions
- resultnat force is dependent on angles of pull and magnitude
Force couple
Two or more forces acting in equal but opposite directions to facilitate a rotation
Torque
A force that causes a rotation about an axis
- increases as the force applied increases or the distance from the axis increases
Torque = force x distance
Moment arm
The perpendicular distance between the force’s line of pull to the axis of rotation
Stabilizing force
Torque that results in compression of joint
- occurs at angles <90
Angular force
As stabilization or dislocation force
- greatest at 90
Dislocating force
Torque that tends to pull a joint apart or destabilizes it
- occurs with angles >90
Pic
Pic
Stability
A state of equilibrium defined by the orientation of the COG relative to the BOS
Stable equilibrium
Can be disturbed or upset only if the COG is elevated
- normal cone
Unstable equilibrium
Minimal force required to disturb or upset
- cone on tip
Neutral equilibrium
COG unchanged when disturbed
- cone on side
Improve stability
- lower COG
- increase BOS
- increase mass
- increase friction
- focus on stationary object
Lever system
Simple mechanical device that makes the work of moving a weight or other load easier
Levers
Provide mechanical advantage either in power or distance (ROM)
- rigid bar (bone)
- fulcrum or axis
- load or resistance
- force (muscle contraction)
First class levers
F - A - R
Favors balance
Second class levers
A - R - F
Favors force and power
Third class levers
A - F - R
Favors ROM
