Exam 1 Flashcards
Biomechanics definition
uses principles of physics to study how forces interact within the living body
Statics definition
bodies at rest
Dynamics definition
bodies in motion
Kinematics definition
motion, relationship between displacement, velocity and acceleration
Kinetics definition
motion, forces that create motion
Center of pressure
center point of weight of a body
Forces acting on the lever=
vector
Forces on the levers are
magnitude, direction, point of application and line of application
Force=
mass x acceleration
Force units
newtons or pounds
Force equilibrium
when at rest, the sum of all forces equals zero
Newtons first law of force
equilibrium-Inertia: a body at rest will remain at rest unless acted upon by a resultant force
Newtons second law of force
acceleration: particle subjected to a resultant force will accelerate in the direction of that force and the magnitude of acceleration will be proportional to the force magnitude.
Newtons third law of force
for every action there is an equal and opposite reaction
Types of forces
gravity, shear, tensile, compressive
Shear forces direction
coplanar; opposite direction
Tensile forces direction
colinear; in opposite direction
Compressive forces direction
colinear; in similar directions to push together
Moment or Torque
the application of force at a distance from the point of pivot. Causes rotation around a stationary point
Moment=
force x distance
Force is the one that is … to the lever.
perpendicular
Distance is the distance from the pivot point to…
point of force applicaiton
Unite of measure for a moment or torque is …
pound-foot or Newton-meter
Moment (torque) has…
magnitude and direction
No moment if force…
passes through the axis
As moment arm increases, the …
magnitude increases
How to draw a free body diagram
covert figure to a free body diagram
label all known elements
make necessary conversions
solve muscle force
Joint reaction force is the… it will be …. to the sum of the x and y vectors.
resultant of all the forces acting on the joint.
equal and opposite
Lever
simple machine used to increase or decrease mechanical advantage, often a rigid bar.
Components of levers
fulcrum or axis of rotation,
force, distance of force arm, resistance, distance of resistance
First class lever
fulcrum between effort and resistance
Second class lever
resistance between effort and fulcrum
Third class lever
effort between fulcrum and resistance
Pulleys may be used to … or … of a system.
change the line of pull or increase mechanical advantage
Pulleys may be … or ….
fixed or movable
Cams are … used to improve the mechanical advantage of a system.
non-uniform ellipses
Cams allow for … throughout ROM to match the length-tension relationship of the muscle.
variable resistance
Fixed pulley characteristics
axis is anchored
pulley wheel only rotates
provides change in direction of force application only
Mechanical advantage=1
Example of a fixed pulley in the body
lateral malleolus and peroneal muscles
Movable pulleys axis
is the attachment point for force but is not fixed
Movable pulley wheel …. and ….
rotates and translates
Movable pulleys provides a change in …
direction of force
Each movable pulley provides a mechanical advantage of …
2
1 pulley requires .. the force
1/2
2 pulley requires … the force
1/4
3 pulleys requires … the force.
1/6
Kinematics is the study of movement related to …
displacement, velocity and acceleration
Kinetics is movement in terms of ..
forces
Impulse is
force applied over a period of time
Work is
force applied over a distance
Inverse dynamics are used to determine…
joint forces
Impulse is…
force applied over time
Power is …
work divided by time
Synarthrosis joints are
non-synovial
Synarthrosis joints is a junction between
bones that allows for slight to essentially no movement
Function of synarthrosis joints
to bind strongly and transfer forces between bones
Types of Synarthrodial joints
fibrous, cartilaginous
Examples of fibrous joints
skull sutures, distal tibiofibular joint
Examples of cartilaginous joints
pubic symphysis, interbody joints of the spine, manubriosternal joint
Diarthrosis joints are
synovial
Diarthrosis joints are a junction between
bones that allow for moderate to extensive movement
Diarthrosis joints contain … and most joints in the body are diarthrodial. Function?
a synovial fluid-filled cavity, to provide motion and flexibility to the frame of the body
Components of diarthrodial joints include
joint capsule, synovium, synovial fluid, articular cartilage, blood vessels, sensory nerves, accessory structures
Mechanoreceptors that provide pain and proprioception in diarthrodial joints include:
Type 1- Ruffini
Type 2- Pacini
Type 3- Golgi
Type 4- Unmyelinated free nerve endings
Where are ruffini mechanoreceptors found?
in fibrous layers of capsule (flexion side), periosteum, ligaments and tendons.
What do ruffini mechanoreceptors do?
inform about stretch and are usually at extremes of extension
Where are Pacini mechanoreceptors found? What do they do?
joint capsule, most deep layers, fat pads; informs about compression or changes in joint movement
Where are Golgi mechanoreceptors found and what do they do?
Found in synovium, ligaments and tendons; informs about pressure and forceful joint motion (at extreme ranges)
Where are unmyelinated free nerve endings found? What do they do?
found in many different tissues (ligaments, tendons, capsule, periosteum); informs about pain/stress
Diarthrodial joints can be classified as..
uniaxial (one degree of freedom); biaxial (two degrees of freedom); triaxial or multiaxial
Types of uniaxial joints?
hinge and pivot
Types of biaxial joints?
condyloid; saddle
Triaxial or multiaxial joints can move
in three planes or three axes
Types of multiaxial joints?
plane; spheroidal (ball and socket)
Three terms in arthrokinematics
roll, glide or slide, and spin
Convex and concave rule in arthrokinematics..
Roll and glide occur in opposite directions for convex on concave; same direction for concave on convex
Connective tissue components
fibers, cells, ground substance
Connective tissue fibers..
collagen (reticulin), elastin
Types of collagen we will focus on
1,2, 9, 10, 11
Type 1 collagen
skin, bone, tendon, synovium
Type 2 collagen
cartilage, nucleus pulposus
Type 9 collagen
hyaline cartilage, vitreous humor
Type 10 collagen
growth plate cartilage
Type 11 collagen
hyaline, often found with type 2
Connective tissue cells
fixed, migratory
Fixed connective tissue cells
fibroblasts, osteoblasts, chondroblasts
MIgratory connective tissue cells
lymphocytes, macrophages
Connective tissue ground substance components
water, glycosaminoglycans, proteoglycans
Connective tissue properties
stress (psi), strain (%), bending, torsion, tension, compression, shear
Connective tissue properties
viscoelastic: plastic, elastic, creep, fatigue
Viscoelastic material properties
time-dependent; rate-dependent; hysteresis (elastic)
Time-dependent definition
longer load=greater deformation
Rate-dependent definition
better resists loads applied more quickly than those applied slowly
Hysteresis definition
energy dissipates due to internal friction
Young’s Modulus
stiffness-how much a substance will deform in response to a force
Cellular components of bone
osteoblasts, osteoclasts, osteocytes, bone lining cells
Osteoblasts
bone formation
Osteoclasts
bone resorption; bony surface and highly mobile
Osteocytes make up ….% of all the cells in bone.
90%
Bone structure
cortical (compact), cancellous (spongy)
Cortical bone is/has
mechanical strength; resists torsion and bending
Cancellous bone is
metabolic activity and highly vascular
Wolffs law for bone?
bone is laid down in areas of high stress and resorbed in areas of low stress
What is the optimal stimulus for bone regeneration?
loading along the axis of the bone
Zone 1 cartilage is
10-20%; superficial, water, collagen in horizontal, resists gliding/shear forces
Zone 2 cartilage is
40-60%;transitional, has increased
volume, hyaluronic acid, collegen
Zone 3 cartilage is
30-40%; deep, cells columnar, collagen perpendicular, tidemark
Zone 4 cartilage is
zone of calcified cartilage, small # of cells
Cartilage function
dissipates and disperses forces/load; minimizes friction; protects bone
Articular cartilage is …
avascular
How does cartilage receive nutrition?
receives nutrition through compression and decompression of joint surfaces
Fibers of tendons
type 1, dense and parallel, oriented in line of tension
Cells in tendons
fibroblasts, tenocytes
Ground substance in tendons
H2O (60-80%); proteoglycan
Myotendinous junction is the …
weakest
Activity of tendons I, II =
III, IV=
physiologic; overuse
Tendon’s functions
transmits muscle force to bones to move or stabilize joints, they resist tensile forces, prone to degenerative changes due to lack fo blood supply.
Fibers in ligaments
Type I (less than tendons); varied arrangement, oriented in line of tension
Cells in ligaments
fibroblasts
Ground substance in ligaments
water; proteoglycans
Ligament function
joint stabilization, provides passive guidance of joint as it moves through range of motion, provides sensory feedback through mechanoreceptors
What is the optimal stimulus for regeneration or healing of tendons or ligaments?
tensile stress in the line of fiber orientation
Skeletal Muscle types
fusiform
penniform
Fusiform skeletal muscles are what direction and responsible for what?
parallel
velocity
Penniform skeletal muscles are what direction and responsible for what?
pennate
force
Examples of penniform muscles
uni-pennate lumbricals
bipennate-rectus femoris
Multipennate-glute or deltoid
Type I muscle fibers are more common with crossing
one joint
Type II muscle fibers are more common with crossing
two joints
Type I muscle fibers are more concerned with… they are ….to atrophy and prone to….
arthrokinematics
first
weakness
Type II muscle fibers are more concerned with ….they prone to ….and dominate with….
osteokinematics
tightness
fatigue
Motor end plate
pocket formed around motor neuron by sarcolemma
Neuromuscular cleft
short gap between motor neuron and muscle cell
Summation
repeated stimulation of a muscle that leads to an increase in tension compared to a single twitch
Tetanus
highest tension developed by a muscle in response to a high frequency of stimulation
Motor unites are recruited on the basis of …
size principles
… more …. units being the first to be used followed by larger and more powerful units. The order is ….
With smaller, more fatigue resistant
constant
What factors influence EMG output?
- electrode size and configuration
- range and size of frequency content of the signal
- magnitude of cross-talk from nearby muscles
- location of electrodes relative to motor unit endplates
- orientation of the electrodes relative to the muscle fiber
- Cleanliness of skin (impedance)
Why with eccentric contraction can you elicit greater forces at faster speeds?
Viscoelastic properties of muscle
Moment arm distance influences
torque production
Muscle length influences …
force production
For the same muscle force production, the scenario with the …… will have the greatest torque.
largest moment arm
Isotonic
fixed resistance, variable speed
Isometric load… torque… speed.
Load: accommodative
Torque: variable
Speed: none
Isotonic load…torque…speed..
Load: Constant
Torque: variable
Speed: variable
Isokinetic load… torque… speed..
Load: accommodative
Torque: variable
Speed: constant
Elastic (Isodynamic)
Load: variable
Torque: variable
Speed: variable
Strength training programs can result in …. gains in strength within 3-6 months.
25-100%
When immobilization is reduced what muscle fibers are affected first? Other things that happen?
slow twitch; decrease in mitochondrial volume; protein synthesis decrease; endomysium thickening; length variation
MMT definition
a clinical procedure which manually assesses muscle strength and/or the contractility of a muscle.
MMT can be performed on a
functional pattern or on a specific muscle
Differential diagnosing from resistance testing: Strong and painless Strong and painful Weak and painless Weak and painful
no lesion or neurological deficit involving the tested muscle or tendon;
minor lesion of the tested muscle or tendon;
disorder of nervous system, neuromuscular junction or a complete rupture of the tested muscle or tendon or disuse atrophy;
serious pathology or acute inflammatory process; or partial rupture; or minor muscle damage
Indications for MMT
postural asymmetry; pain; reported weakness/fatigue; mechanism of injury; difficulty with function; prolonged disuse
Gross testing for MMT
very common, assesses function of a patient
Specific testing for MMT
differential diagnosis; identify specific peripheral nerve lesion; nerve root involvement; spinal cord lesion involvement; specific anatomical structure change
Types of MMT
break testing;
active resistance testing;
functional muscle testing;
quick strength screen
Break testing
manual resistance applied to test limb to break a static positional hold. Joint not actively moving through range. Most common.
Active Resistance training
manual resistance applied during an actively contracting muscle or muscle group. Requires more skill from clinician.
Function muscle testing
performance based
Fixation substitution
muscles that normally fixate or hold a joint in place compensates for a weak msucle
Substitution from another agonist
When another prime mover helps move the body part in the direction in the direction being tested
Substitution from an antagonist
when an antagonist helps move the body part in the direction being tested
Active insufficiency
inability of 2 joint mm to perform a concentric contraction over one joint when it is shortened over the other. Example: hamstring
Passive Insufficiency
inability of 2 joint mm to lengthen over one joint when it is already lengthened over the joint. Example: rectus femoris
Numerical score for grading vs qualitative
5=normal, 4=good, 3=fair, 2=poor, 1=trace, 0=no activity
Different grading scales
kendalls;
Daniels and Worthingham (break testing);
ART
MMT, if AROM is full score… and use …. test……
3/5;
break test or ART
MMT, if AROM is limited check….
PROM
MMT, if AROM is limited and checked PROM, if it is greater than AROM score…. if it is = to AROM use….
3/5;
break test
Criteria for using ART
wanting to assign a + or - grade. OR you want to precisely test the strength of a muscle through the available range of motion.
Criteria for using BT
PROM=AROM; want to test muscles of the cervical spine or small digits and scapula; quick screen
What do you document from MMT?
type of grading system; position of patient; actual grade of muscle strength; anatomical part and the type of movement; comparison of both sides; presence of pain during testing
When is MMT not appropriate?
children or infants; people with upper motor neuron lesions where significant tone is present
