Basic Biomechanics ch.2 Flashcards
function of the musculoskeletal system is described by a branch of physics termed ?
mechanics
structure
anatomy
function
physiology
mechanics
study of forces & the effect of application of forces on stability & motion of the body
2 main areas of dynamics
static
dynamic
factors associated w/ non-moving systems
tasks; sitting, laying down
static
2 factors associated w/ moving systems: kinetics & kinematics
ex; walking, rolling in bed
dynamics
forces producing stabilization or movement in a system
kinetics
motion created by forces & incorporates time, space, and mass
ex: running & walking
kinematics
kinematics is divided into 2 types
osteokinematics
arthrokinematics
quantity describing only magnitude
speed (M/H), length, area, vol, & mass
scalar
the amount/aggregate of matter in an object
(human body)
mass
magnitude & direction. common measures force, velocity, and acceleration
vector
indication of amount of measurement
magnitude
the direction in which the magnitude is applied
(flexion/extension)
direction
amount & direction of push/pull applied to objects or body segments
force
push creates?
compression
pull creates?
traction (pulling apart)
2 types of forces?
internal
external
mutual attraction bt. earth & an object?
gravity
external forces include?
gravity
external pressure (weights or friction)
internal forces include?
muscle contraction
ligamentous restrained
& bony support
the force exerted on an object/person as a result of gravity
gravitational force
result of gravitational force & mass of an object always pushing down
weight
the upwards force supporting surface exerts on an object (person) when a person pushes down on it
ground reaction
- no ground reaction = fall into eternity
force bt. 2 surfaces that increase resistance to motion of 1 surface across another
increased by compression (rubbing)
decreased by traction
friction
types of different configurations of force
linear - 2+ forces act along the same line
parallel - same plane & in the same/opposite direction
concurrent - push/pull in different directions - goes diagonally
occurs when 2 or + forces act in different directions, producing a rotation.
ex: scapula
force couple
sum of the magnitudes & directions of each individual force vector
ex: deltoid muscles
resultant force
5 mechanical effects of force application to body
traction
compression
shear
bending
rotation (twisting)
joint surfaces pull apart
traction
why? reduce compression to decrease pain. too much = dislocation
joint surfaces push closer together?
ex: running, squats, jumping
compression
why? stability and strength. too much = cartilage problems & compression fx
gliding motion of joint surfaces parallel to 1 another
ex: knee extension
shear
Why? reduce pain alleviate movement. too much = tissue strain/rupture
2 opposing forces twisting within an object in opposite directions
ex: ACL injuries
torsion
excessive torsional forces = ligament tear or spiral fx of bone.
force is not applied at the central axis. causes compression to one side and traction to the opposite side
ex: spinal trunk bending/flexion
bending
tendency of a force to produce rotation about an axis
torque
is muscle more efficient at 90 degrees for creating rotary motion?
yes! it is less efficient if jt angle is near the beginning or end of the jt’s ROM
the perpendicular distance bt. the line of application of force & the axis of motion
moment arm
newtons 1st law
object stays at rest or in motion unless acted upon by an external force
law of inertia
amount of torque generated depends on
amount of force applied
distance from axis that force is applied
ex; pt seated, my hand @ the ankle vs knee as resistance
what is the angle at which force is applied ?
the angle of application of force
-force can be applied perpendicular = torque or at an angle to the limb
lower extremity in swinging phase of gait
force required to start: hip flexors
force required to stop leg: hamstrings
newtons 1st law, law of inertia
newtons 2nd law: acceleration depends on the strength of the force applied to the object
law of acceleration
adding ankle weights for a greater muscle force needed to start & stop a leg swing
newtons 2nd law, law of acceleration
acceleration is inversely proportional to the ___ of an object and directly proportional to the amount of ___
mass, force
trampoline, the harder you jump the higher you rebound
newtons 3rd law, law of action-reaction
newtons 3rd law: force applied creates an equal & opposite reaction
law of action-reaction
sum of the mass of all body segments is located
Center of mass (COM)
when the sum of all forces acting on an object = 0
equilibrium
- no motion occurs
- also dependent on COM, COG, & BOS of the object
the area encompassed by the body’s contact w the supporting surface
Bas of supports (BOS)
point at which gravity acts on the COM
slightly anterior to S2
Center of gravity (COG)
imaginary vertical line passing though the COG to the center of the earth
Line of gravity (LOG)
types of motion
linear motions (translatory)
curvilinear motion
angular motion (rotary)
all parts of an object move the same distance at the same time
ex: kid sledding down a hill
linear motion
motion occurring in a curved path, not circular
ex: skier takes curved path coming down a slope
curvilinear motion
movement of an object around a fixed point (axis)
ex: knee joint for flex/extension
angular motion
types of simple machines
levers
pully
inclined planes
axes
joint
levers
bone
force
muscle & weights
rigid “plank” rotating about a fulcrum with application of force
lever
what class lever is the skull on the 1st vertebrae?
1st class
force = ant/post muscle
axes = skull and vertebrae
resistance = weight of head
what class lever is a person rising on their tippytoes?
2nd class lever favor force
axis = metatarsophalangeal (MTP) foot
resistance = body weight pushing down
force = plantar flexor muscles
what class lever is the biceps brachii muscle flexing the elbow ?
3rd class lever
axis = elbow jt
force = biceps brachii muscle
resistance = weight of arm/forearm
whats the most common lever in the body?
3rd class level - favor distance
force is gravity
2nd lever
what lever results in resistance is gravity, force is a muscle
3rd
a grooved wheel that turns about an axis w a rope/cable tie ridding in the groove provides attachment for an applied force & a load
pulley - used to change the direction of a force or change the magnitude
the “wheel” is the bone
“rope” is tendon or muscles
2 types of pulley’s?
fixed pully
moveable pully
a single pulley attached to a fixed point, creating a 1st class lever configuration
fixed pully
ex: lateral malleolus & fibularis longus or patella w the quad
or overhead and wall pulley in clinical setting
T/F: there is no moveable pully in the human body
TRUE
combines a fixed pully to change direction & a moving pulley to change magnitude of force applied to lift a load
movable pully
inclined ramp?
a flat surface that slants from one level to another
federal requirement for slope of wheelchair ramp?
1inch rise & 1foot run
