Midterm #2 Flashcards
what is tissue mechanics
mechanics of materials of human connective tissue
human connective tissue
bones
ligaments
cartilage
tendons
load
an externally applied force
what does the respond of an object to a load depend on
magnitude location direction duration frequency variability rate
types of load
axial (tension, compression) bending shear torsion combined loading
axial force - compression
push or squash molecules of a material otgether
deformation by shortening
what is compression/tension response proportional to
body´s cross sectional area
axial force - tension
pull apart object´s molecules
deformation by stretchng or elongating
shear
transverse force
force that causes one part of body to move parallel past another part
what can shear loading lead to
on skin - blisters
on tibia and femur - tension in ligaments
torsion
rotational load
twisting around axis
depends on distribution of material around axis
bending
compression on one side
tension on the other side
loading applied perpendicular to longitudinal axis
what determines the effects of bending on the body
cross sectional area
distribution of material
length of the body
what causes injury
load > tissue tolerance
load > tissue strength
biological material quantitiy
size -> amount of material distribution
bilogical material quality
ingredients of the tissue
factors affecting tissue strength
material
amount of tissue
distribution of tissue
what is distribution of tissue
how tissue is soread
area of moment of inertia - a measure of a body´s resistance to bending
tissue tolerance
relationship between load imposed (external force) and the amount of deformation (internal reaction) of material
load deformarion
effects of load on different tissue sizes and materials
chnage of shape of tissue
stress strain
stress = load/size
effects of stress on material and tissue
change in length normalized to original length
stress
property of object under pressure
force over small area will cause larger stress
e.g. tennis shoes vs. spike heels
unit of stress
N/mm(squared)
relation of load/stress on vertebrae
load: increases from cervical -> lumbar
stress: decreases from cervical -> lumbar
descriptors of strength
ultimate strength yield point stiffness deformation energy failure point ductility brittleness
different types of injury
acute load injury
repretitive load injury
prolonged load injury
what factors contribute to injury
age gender genetics physical condition fatigue environment ...
stiffness
relates load and deformation
elastic region
no permanent change in tissue
recovers all energy
used to deform tissue
plastic region
energy used to permanently change the shape of the tissue
yield strength
load/stress at which plastic deformation begins
ultimate strength
max load/stress
fracture strength
load/stress at point of fracture
ductility
amount of strain material can undergo before fatigue
brittleness
minimal (no plastic) deformation of tissue
toughness/energy under the curve
work required to produce deformation
types of bones
cortical bone (solid) trabecular bone (has holes)
bone mass over time
males have greater peak bone mass
males have greater rate of gain for BMC
females have decrease in bone mass around menopause age 45-60
bone cells
osteoblasts - bone formation
osteoclasts - take away of old damaged bone
osteocytes - mature osteoblasts during formation
steps of bone formation
activation
resorption
reversal
formation
exercise for bone strengthening
weight bearing activities
short duration
mderate to intense magnitude
long rest periods
why is summer good for bones
increase in vitamin D
more physical activity
bone content
65% inorganic substance (clacium)
35% organic substance (collagen)
responsibility of calcium in bones
many functions
heartbeat
conducting nerve impulse
muscle contraction
parts of female athlete triad
low energy availability/disordered eating
bone loss/osteoporosis
menstrual disturbances/Amenorrhea
areas of bone cross section
periosteal merimeter endocortical perimeter endocorticol perimeter total area cortical bone area periosteal diameter endocortical diameter
law of inertia in angular kinetics
body remains at rest or constant anular velocity around an axis of rotation unless external torque changes its state
mass moment of inertia (I)
body´s resistance to a change in angular velocity
what does the mass moment of inertia (I)depend on
mass and distribution
in what unit does the mass moment of inertia get measured
kgm(squared)
claculation of mass moment of inertia (I)
I = m r(squared)
law of acceleration in angular kinetics
angular acceleration of body is directly proportional to the torque causing it
takes place in same rotary direction as torque acts
inversely proportional to mass moment of inertia of the body
torque in angular kinetics
torque = mass moment of inertia x angular acceleration
will cause acceleration of body around axis of rotation
angular momentum -> rotating disk (extended object)
L = I x angular velocity
angular momentum tether ball (pointy object)
angular momentum = radius x linear velocity
L = r x p (linear momentum m x linear velocity)
conservation of angular momentum
when gravity is only force acting on object, angular momentum will stay the same even if radius of object changes
maximal efort
range of motion
speed of motion
hat is maximla performance a reult of
max effort
summation of joint torques
continuity of joint torques (usage of kinetic link principle)
goal of the kinetic link principle
achieve max angular velocity of distal segment
what does the kinetic link principle say
beginning movement with large segments, smaller segments initiate contraction at the point of maximal angular velocity and zero angular acceleration
timing is important
taking torque of one joint into movement of another joint
angular impulse to momentum relationship
angular impulse = angular momentum
T x delta t = I x angular velocity
law of action reaction in angular kinetics
for every torque there is a equal and opposite directed torque
what kind of objects experience centripedal force
any that move in circular path
includes forces that push or pull objects towards center of circle
centripedal force
describes direction of force
alters the direction of the object without altering its speed
what can a muscle tendon complex act at as
motor, brake, rubber-band, strut
phases of a jump
propulsive phase
braking phase
both phases are on the ground
propulsive phase
upward phase
from initiation of upward movement to the instant of takeoff
braking phase
downward phase from the instant of landing to the max dorsiflexion
concentric contraction in upward phase of a jump
MTC develops greater force than external force
muscle shortens
force and displacement same direction, MTC - positive work
MTC increases energy of skeletal system
MTC acts as energy source or motor
eccentric contraction in downward phase of a jump
MTC develops less forc ethan external force
muscle lenghtens
force and displacement opposite directions
body is losing energy
MTC acting brake, absorbing the energy
what is a stretch shortening cycle (SSC)
an eccentric contraction followed by an immediate concentric contraction of a muscle
Isometric contraction
motion MTC develops equal force to external force muscle length does not change no displacement -> no work MTC acts as a stabilizer
functional unit of muscle
sarcomere
what does sarcomere include
contractile protein (actin, myosin) non-contractile protein (titin and desmin)
resting length of sarcomere
2 micrometer
from z line to z line
muscle structure
acting myosin are myofilaments -> myofilaments active parts of sarcomere -> string of sarcomere = myofibril ->multiple myofibril = muscle fiber -> group of muscle fiber = fasicle -> group of fasculi = muscle belly
titin and desmin
in sarcomere
a series of elastic components (SEC)
extracellular connective tissue (PEC)
made of collagen and elastin endomysium wraps one muscle fiber perimysium wraps one fascicle epimysium wraps muscle belly parallel elastic components (PEC) continous with tendons on both ends
elastic property of PEC and SEC
provide force only when stretched
force transmitted to bone
viscous prperty of PEC and SEC
increased velocity of stretch increases the passive force produced
when do non-contractile (passive) components develop tension
when muscle is lengthended beyond resting length
theory for muscle as brake - eccentric contraction
titin increases stiffness -> contributes to force production as muscle lengthens
small contribution from elastic elements of cross bridges
theory of muscle as a strut - isometric contraction
muscle shortens, tendon lengthens
greatest isometric force as mid range of muscle length
load-deformation relationship in non-contractile components
linear
interaction of muscle and tendon
independently
can work in different directions or velocities
short tendons work at same displacement and velocity as muscle
what does the force produced in a muscle depend on
# of cross bridges formed length of muscle
what does the ability to form cross bridges depend on
muscle length
too long -> actin is out of range
too short -> overlapping, less force to produce
when does passive tension contribute to force production
only when muscle is stretched beyond resting length
what oes the combination of active and passive tension allow
large range of muscle forces over a wide range of muscle length
active indufficiency of two joint muscles
muscle force is limited due to short length (length tension curve)
passive insuffiviency of two joint muscle
A muscle will limit range of motion at a joint because it is over-stretched over two joints
force velocity curve/relationship
max force during high eccentric velocity
lowest force during high concentric velocity
medium force during isometric contraction
power
force x velocity
peak at intermediate velocity
muscle actions
agonist antagoinst synergist stabilizer neutralizer isokinetic isotonic
agonist
prime mover
muscle that produces motion
antagonist
opposite of motion creating
get stretched
synergist
muscle that work together to produce motion
when working alone they produce different motion
stabilizer
muscles that support movement
neutralizer
shoulder extensor neutralizes biceps shoulder flexion during biceps curl
isokinetic muscle action
constant velocity of contraction
concentric and eccentric contraction
isotonic muscle action
constant load throughout contraction
free weights
torque changes throughout motion
what does bone remodeling include
bone formationa nd bone resorption
what does bone modeling refer to
large changes in bone during normal growth
one thing we can do to combat female athlete triad
balanced diet - including calcium and enough energy for growing active athlete
provide enough rest periods
