Chapter 7: Biomechanics Flashcards
What are the anatomical planes of movement?
sagittal
frontal
transverse
What plane divides the body into right and left segments?
Sagittal plane
What’s an example of the sagittal plane?
Flexion and extension
What plane separates the body into ventral (anterior) and dorsal (posterior) segments?
Frontal (coronal) plane
What plane separates the body into superior and inferior segments?
Transverse (axial) plane
What’s an example of the frontal (coronal) plane?
abduction, adduction, and lateral
What’s an example of the transverse plane?
Rotational movements
What are the 3 primary joints forming the shoulder girdle?
The glenohumeral (GH) joint
The acromioclavicular (AC) joint
The sternoclavicular (SC) joint
The study of mechanical laws related to movement or structure is called . . .
Biomechanics
What are the two main types of biomechanic systems?
Dynamic and static
What do we call systems in motion with acceleration
that create uneven forces acting on the body?
Dynamic systems
What are the characteristics of static systems?
At rest
No acceleration
Still with no motion
Constant motion with no acceleration
What is velocity?
The direction and rate of displacement
What’s the difference between kinematics and kinetics?
Kinematics describes motions of the body
Kinetics describes the forces acting on a body in motion
What’s the most common mechanical machine with the body? What does it consist of?
Lever systems, which consist of a bar and an axis
How do levers function?
Levers rotate around an axis as a result of force applied to move weight or applied against resistance
What’s another name for an axis and force?
Fulcrum
Load or effort
The bones are the . . .
The joints are the . . .
The muscles contract to . . .
levers
axes
apply force
What’s the common lever?
Third-class
What is torque?
Turning effect of force applied to the various levers to create movement
What is eccentric force?
Force applied in a direction not in line with the center of rotation when an axis is fixed, necessary for rotation
How is torque determined?
Force x length x distance (fulcrum and the force)
How does torque affect human movement?
The length of the lever determines the amount of velocity
For example, a tennis player can strike a tennis ball harder and with more velocity with a straight arm than with a bent elbow
When is a shorter level preferred?
When speed is desired instead of velocity
What mechanisms enhance range of motion and speed or change the direction of movement?
Wheels, axles, and pulleys
What are the laws of motion?
Motion of the human body is always initiated by a muscular contraction
These contractions initiate and propagate movement and are the source of force
What are two types of motion for human movement
Linear: Movement along a line (straight or curved)
Angular: Rotation around an axis
What law of motion describes the distance an object is displaced from its starting point?
Displacement
What law of motion refers to the total or sum of the length of travel?
Distance
What law of motion refers to the change in location of a rotating object?
Angular displacement
What law of motion describes the distance an object moves in a straight line
Linear displacement
The biomechanical system maintains the current motion whether the body or a segment is moving or at rest. What’s the only thing that can change the status of movement?
force via muscular contraction
The change of acceleration is directly proportional to the ___ causing it and ____ proportional to the mass of the body
Force
Inversely
What provides the reactionary force in opposition to the force of the human body?
Surface, aka friction
What is the force created by the resistance between two surfaces of two objects moving across one another?
Friction
What are the 3 types of friction?
Static friction: The friction between two objects not moving
Kinetic friction: The friction between two objects moving across one another
Rolling friction: The friction when one object rolls across a surface
What is constantly challenged in human movement?
balance, equilibrium, and stability
What is balance?
The ability to control equilibrium
What is equilibrium?
A state of no acceleration with the body at rest
What is stability?
Resisting changes to the body’s acceleration or equilibrium
What is the state in which all objects desire to be?
Equilibrium
When is it possible to achieve static equilibrium?
When the body is at rest
What is the state when the body is moving at a steady and unchanging speed or direction?
Dynamic equilibrium
When is stability maximized?
When the center of gravity can be determined and, if necessary, shifted
What is the point at which both body mass and weight are equally distributed?
Center of gravity
Momentum =
Mass x velocity
What are the two types of loads?
external or internal forces
What gives rise to internal loads?
Muscle contraction
What are the 5 types of stress from mechanical loading?
Tension: stretching or strain Compression: reducing in volume and increasing in pressure Bending: shaping into a curve or angle Torsion: twisting Shearing: cutting or breaking
What’s the best way to avoid deformations on the body from mechanical stress?
Absorbing force over a larger part of the body over time
A joint has only the ability to . . .
Rotate
What is always opposite of the direction of rotation?
Direction of resistance
What is flexion?
Movement decreasing the angle between two body parts
What is extension?
Movement increasing the angle between two body parts
What is abduction?
Movement away from the midline
What is adduction?
Movement toward the midline
What is medial rotation?
Rotational movement toward the midline
What is lateral rotation?
Rotational movement away from the midline
What is elevation?
Movement in a superior direction
What is depression?
Movement in an inferior direction
What is a triplanar motion occurring from dorsiflexion, eversion, and abduction?
Pronation
What is the combined motion of plantar flexion, inversion, and adduction?
Supination
What causes a bone to rotate around its axis?
The contraction of muscles, which creates an eccentric force
What are the following?
Motion of the human body is always initiated by a muscular contraction
These contractions initiate and propagate movement and are the source of force
Laws of motion
