Midterm #3 Flashcards
sensory receptors in the muscle
muscle spindle
golgi tendon organs
charcteristics of muscle spindle
located parallel to muscle fibers
monitor muscle lenght
limits stretch in muscle
which muscle fibers/at what state do muscles need to be to be excited or inhibited by the muscle spindle
excitation of stretched muscle fibers and synergist muscle
inhibition of antagonist muscles
location of golgi tendon organ
muscolotendinous junction
charactersitics of golgi tendon organ
stimulated with stretch of tendon
inhibits muscle contraction
threshold can be changed with practive
protective mechanism
mechanism of stretch shortening cycle
storage of enery in PEC and SEC
stimulation of muscle spindle reflex
algnment of cross bridges in slack muscle fibers
eccentric activation give more time for slow twitch fibers to develop tension
what is a motor unit
a nerve and all the muscle fibers it innervates
two main strategies of motor nuron activation
recruitment
rate coding
what do the main strategies of motor neuron activation allow
large range of force
gradual change in force
recruitment
activation via action potential of specific motor neurons
cause excitation and activation of muscle fibers
result of recruitment
a muscle twitch - contraction
muscle fibers within a motor unit
share similar characteristics
distirbuted randomly across muscle
1 muscle fiber controls 5-2000 muscle fibers
lower innervation ratio
small # of motor units recruited
accurate movement
high innervation ratio
large # of motor units recruited
henneman size principle
small motor units recruited first then larger and large motor units
allows smooth and controlled increase in force
rate coding
the force produced by motor unit is strongly regulated by rate of production of action potentials
discharge rate of rate coding
from 10hz, 100ms intervals, up to 50hz
twitch related to rate coding
messgae send as an interval
unfused tetanus
no breaktime in incomeing APs
fused retnus
maximal contraction
how does a motor unit create greater overall force
when its activated at a higher rate
eccentric activation
less motor units recruited compared to concentric
what does it require to initiate a fast strong isometric contraction
use of rate coding
component of muscle force
rotary component
stabilizing component/destabilizing component
rotary component
causes rotation
perpendicular to the bone of insertion
stabilizing/destabilizing component
stabilizes or destabilizes joints
parallel to bone of insertion
causes compression or distraction
muscle adaptations to training
hypertrophy
hyperplasia
hypertrophy
muscle growth -> increase in muscle force
increase in size of each muscle fiber
no change in # of fibers
hyperplasia
increase in # of muscle fibers
neural adaptation to training
increased strength without changes in cross sectional area increased recruitment and rate coding motor unit synchronization increased coordination inhibition of golgi tendon organ
increase in force production but no increase in EMG
strength gain due to neural factors
increase in EMG in direct correlation to the increase in force
strength gain due to hypertrophy
increase in force greater than increase in EMG, and increase in both
stregth gain due to neural factors and hypertrophy
what can strength training be largely attributed to
motor unit activation of the trained agonist muscle
when does chronic load lead to lengthened muscle adaptation
increase in sarcomere # by 20%
when does chronic load lead to shortened muscle adaptation
decreased sarcomere # by 40%
where are sarcomeres added
at the musculotendinous junction
which muscles are most adaptable
antigravity muscles
what will chronic use of high heels lead to
increased risk for lateral ankle sprain (increased plantarflexion)
increased risk for achilles tendon injury
categories of muscle architecture
longitudinal (fusiform)
pennate
longitudinal muscle arrangements
anatomical and physiological cross sectional areas are equal
subsection of longitudinal muscle arrangements
fusiform
strap
radiate
subsections of pennate muscle arrangements
unipennate
bipennate
multipennate
unipennate muscle arrangements
one group of muscle fibers parallel to each other but oblique to the tendon
bipennate muscle arrangements
two groups of muscle fibers
oblique to each other an to tendon
within the group fibers parallel to each other
multipennate muscle arrangements
more than 2 groups of fibers
fibers are parallel to each other within the group but oblique to other groups and tendon
physiological cross sectional area
perpendicular to muscle fibers
anatomical cross sectional area
perpendicular to midline of muscle
what does a greater pennation lead to
greater physiological cross sectional area -> larger force
different sarcomere arrangements within a muscle
parallel
in series
which sarcomere arrangement has larger physiologicalcross section area (greater force)
parallel sarcomere
what advantage have sarcomeres in series
fast control of range of motion
what does the length of a muscle influence
the speed and distance a muscle can shorten
what is one gait cycle
step with left leg followed by step with right leg
same as 1 stride
1 stride length (gait cycle length)
144 cm
walking speed
step length x step rate
stride length x stride rate
phases of a gait
reference limb stance phase swing phase single limb support double limb support
what are the 3 tasks performed during 1 stride
accept weight on foot once it is on the ground
support weight on single leg
advance swing limb in front of body
critical elements for each phase of gait
weight acceptance
single limb support
swing limb advancement
weight acceptance
intial contact, loading response contact floor with heel stabilize hip restrain knee flexion restrain ankle, plantar flexion
single limb support
midstance -> stabilize hip in frontal plane, extend knee, restrain ankle dorsiflexion
terminal stance -> forward free fall, raise heel
swing limb advancement
preswing, initial swing, midswing -> flex knee and hip, dorsiflex ankle
terminal swing -> decelerate ankle and knee extension, neutral position of ankle
external forces during gait cycle
Ground Reaction Force
weight of body
intersegmental torque
internal forces acting during gait cycle
active - muscles
passive - connective tissue
what dictates the type of external torque created at a joint at a specific time of the gait cycle
location of ground reaction force
what torques are generated by ground reaction force at heel contact
plantar flexion torque
eversion torque
where oes most of the torque for propelling the body forward come from
ankle plantar flexion 53%
hip flexion 30%
peak ground reaction forces during gait cycle
certical -> 120% BW
anterior-posterior -> 20% BW
medial-lateral -> 5% BW
running phases by Dr. Jackuelin Perry
stance
early float
middle swing
late float
stance
right heel strike to right toe off
35% of gait cycle
single limb stance
early float
right toe off to left heel strike
15% of gait cycle
both limbs are in the air
middle swing
left heel strike to left toe
35% of gait cycle
contralateral limb is in single leg stance
late float
left toe off to right heel strike
15% of gait cycle
both limbs in the air
ratio of stance to float in running
35% stance
65% float
phases within stance
loading response
mid stance
terminal stance
hip knee and ankle at lowest point of stance
hip 25F
knee 40F
ankle 20DF
ankle knee and hip motion during swing
ankle from 30 PF to 5 DF
knee from 10F to 100F
hip 10 Ext to 30F
what does float in running replace from walking
double limb support
approxx. 2.1 m/sec
stance in walking and running
drops from 60% to 35%
angular displacement
is larger during running at the hip and the knee
foot position during running and walking
running -> rearfoot striker/midfoot and frontfoot
walking -> rearfoot
ankle position in running vs. walking
running -> neutral position at initial contact, followed by dorsiflexion
walking -> neutral to plantar flexion
magnitude relation in walking vs. running
forces magnitude 2-4 times larger in running
highest/lowest potential energy during walking
highest: midstance
lowest: double limb support
highest lowest kinestic energy during walking
highest: double limb support
lowest: midstance
energy during running
elastic energy
kinetic energy
potential energy
kinetic energy during running
highest in float phase
potential energy during running
highest during float phase
major clinical problems faced by runners
muscle pveruse
pressure of floor contact
mechanics of eccentric contraction
what bones are at greater risk for injury during running
the first 3 metatarsal heads and the big toe
what may prolonged running lead to
stress fructure
what can help muscles to reduce risk of injury during running
strength and flexibility training
muscles that contract eccentrically
RF Vastii BFSH BFLH semimembranosus
when and where does strain occur
in tnedon and aponeuroses while muscles are contracting isometrically
what does faster running require
rapid and severe lengthening of tendons and aponeuroses
what can be done to prevent running injuries
increased strength and endurance of muscles
progressive tissue adaptation to eccentric load
cushioning
what is classified as fluids
liquids and gases that flow and change shape
fluid mechanics
study of forces tha fluids exert on objects
two different forces
buoyant force
dynamic force
characteristics of buoyant force
due to immersion in fluid
vertical force
always acts upwards
what causes buoyant force
increase in depth -> linear increase in pressure
equation of buoyant force
pressure = force / unit area
2 findings of archimedes related to buoyant force
buoyant force is difference between the force acting upward and downward on an object
also equlas the weight of the volume of fluid displaced by the object
what should the weight of an object be to float
needs to be equal to the weight of the fluid
weight of an object to accelerate up/down in water
accelerate up -> object needs to be lighter than the weight of the fluid
accelerate down -> object needs to be lighter to accelerate down
specific gravity
weight of an object / weight of an volume of water
what is another way to determine if an object sinks or floats
density = mass/volume
dynamic fluid force
force due to relative motion
what is dynamic fluid force proportional to
fluid density x surface area of the object x relative velocity
relative velocity
compares my velocity to the velocity of air
difference between both the velocity of fluid and an object
in what is dynamic fluid force resolved into
drag force
lift force
drag force
acts in opposite to relative motion of the object
will tend to slow down the relative velocity of the object
produced by surface drag and form drag
calculation of drag force
1/2 coefficient of drag(roughness of surface) x density of fluid x area of object x relative velocity (squared)
surface drag
sum of driction forces between fluid and suface of object
what increases surface drag
higher viscocity
form drag
sum of impact between object and fluid molecules
increases as the amount of turbulent flow increases
turbulent flow
fluid molecules separate from the surface
laminar flow
molecules of the fluid stay close to the object and press against it
what reduces stream force
smoother body surface streamline the shape of the body lower air density - warmer air reduce surface area exposed to flow use wind drafting
lift force
dynamic fluid component that acts perpendicular to relative motion of object
direction of lift force
determined by direction of flow of fluid
perpendicular to the flow of fluid
what causes lift force
lateral deflection of fluid molecules as they pass an object
what kind of force is used at an airfoil
the net force generated is lift force
Bernoulli´s Principle
faster moving fluids exert less pressure than slower moving fluid
fluids on a curved surface move faster than on a straight surface
why did ski jumpers change the position to a V position
to increase the surface area -> increase the lift
magnus effect
curving of a ball in the air
if backspin, motion of the air molecules at the top of the ball is slower
motion of air molecules at the bottom of the ball move faster
down motion of ball due to Bernoulli´s Priniple
