Chapter 1 - Basics Flashcards
kinematics
describes the motion of a body, without regards to the forces or torques that may produce the motion
translation
a linear motion in which all parts of a rigid body move parallel to and in the same direction as every other part of the body
rotation
a motion in which an assumed rigid body moves in a circular path about some pivot point
active movements
movement of the body caused by stimulated muscle
passive movements
movement of the body caused by sources other than muscle
osteokinematics
the motion of bones relative to the planes of the body: sagittal, frontal, and horizontal
axis of rotation
the pivot point for the angular motion
- movement plane is perpendicular to axis of rotation
- typically located through the convex member of the joint
degrees of freedom
number of independent movements allowed at a joint
- maximum of 3
kinematic chain
series of articulated segmented links
- connected pelvis, thigh, leg, and foot
open kinematic chain
distal segment of chain is NOT fixed to the earth or immovable object
- foot is free to move
closed kinematic chain
distal segment is fixed to the earth or another immovable object
- proximal is free to move
arthrokinematics
motion that occurs between the articular surfaces of joints
Fundamental movements between joints
roll
slide
spin
Roll
multiple points along one rotating articular surface contact multiple points on another articular surface
slide
a single point on one articular surface contacts multiple points on another articular surface
spin
a single point on one articular surface rotates on a single point on another articular surface
Arthrokinematic principles of movement
for a convex-on-concave surface movement, the convex member rolls and slides in OPPOSITE DIRECTIONS
- for a concave-on-concave surface movement, the concave member rolls and slides in SIMILAR DIRECTIONS
accessory motions
“joint play”
- slight passive translations that occur in most joints
- 3 linear directions corresponding to 3 axes of rotation
- test for stability
close-packed positions at a joint
the position of maximal congruency
- where most ligaments and parts of the capsule are pulled taut, providing stability
- usually in very end ROM
- LE = standing and habitual function
loose-packed positions at joint
all other positions that aren’t close-packed
- ligaments are relatively slackened allowing an increase in accessory movements
- LE = flexion and extension
kinetics
describes the effect of forces on the body
F = m x a
Tension
application of one or more forces that pulls apart or separates a material
- distraction force
compression
application of one or more forces that press an object(s) together
- tends to shorten and widen a material
bending
effect of a force that deforms a material at right angles to it long axis
- compressed on concave side and tension on convex side
shear
forces on a material that act in opposite but parallel directions
torsion
application of a force that twists a material about its longitudinal axis
combined loading
combination of different forces applied to an object
stress
internal resistance generated as a tissue resists its deformation, divided by its cross-sectional area
strain
ratio of the tissue’s deformation length to its original length
- lengthening = stretched length:original length
stiffness
ratio of stress to strain in an elastic material
viscoelastic
tissues in which the stress-strain curve changes as a function of time
creep
progressive strain of a material when exposed to a constant load over time
- reason we are taller in the morning
rate of loading
a quality of viscoelastic material
- stiffness increases with increasing rate of loading
- ex: articular cartilage in knee becomes stiffer during running
internal forces
produced from structures located within the body
- may be active(stimulated muscle) or passive(stretched tissue)
external forces
produced by forces acting from outside the body
- ex: gravity, external loads, physical contact
angle of insertion
angle between the tendon and the bone
joint reaction force
push or pull produced by one joint surface against another
static linear equilibrium
no linear movement due to the balancing of forces
internal forces = external forces
productive antagonism
phenomenon in which relatively low levels of tension within stretched connective tissues performs a useful function
- plyometrics
- stretched muscle aids in contraction
moment arm
the shortest distance between the axis of rotation and the force
torque
the product of a force and its moment arm
- rotational force
internal torque
the product of the internal force and the internal moment arm
- IMA = the distance between the axis of rotation and the perpendicular intersection with the internal force
external torque
the product of the external force and the external moment arm
static rotary equilibrium
no rotation occurs at the joint due to the balancing of torques
synergist
muscles that stabilizes to prevent unwanted motion
force-coupled
formed when 2 or more muscles simultaneously produce forces in different linear directions, although the torques act in the same rotary direction
- working together(but in different directions) to rotate
mechanical advantage
the ratio of the internal moment arm to the external moment arm
MA = IMA/EMA
- muscles generally produce forces several times larger than the external loads that oppose them
1st class lever
axis of rotation positioned between two forces
- see-saw
- may have a MA1
2nd class lever
axis of rotation is located at one end of a bone
- internal force possesses greater leverage than the external force
- ex: wheel-barrel, standing on toes at ankle
- always have a MA>1
- internal force always has advantage
3rd class lever
axis of rotation located at one end of a bone
- external weight has a greater leverage than the muscle force
- ex: elbow flexors
- most common in body
- always have a MA<1
