Midterm 1 Flashcards
Lectures 2-10
posture
- biomechanical alignment of the body
- orientation of the body to the environment
ideal posture
eyes, shoulders, pelvis, knees, and medial longitudinal arches are level
factors impacting posture
- gravity and where it passes through the segments
- position of segments
- base of support
- muscles, ligaments, joints
ICF
international classification of functioning, disability, and health
works at the individual, institutional, and societal level
components of the ICF
- health condition
- body structures & function
- activities (limitations)
- participation (restrictions)
- environmental factors
- personal factors
qualifiers of ICF
performance: describe what a person does in their current environment
capacity: ability to execute a task in a specified context at a given moment. Identifies the highest probable level of functioning
measurement
process of assigning numerals to variables to represent quantities of characteristics according to certain rules and procedures
types of data
1) categorical
- nominal
- ordinal
- binary
2) quantitative
- discrete
- continuous (interval or ratio)
categorical nominal data
- unordered categories that are mutually exclusive
- no true zero
- unequal intervals
- no defined order
hair colour, ethnic background
categorical ordinal data
- ordered categories that are mutually exclusive
- no true zero
- unequal intervals
- defined order
BORG scale
categorical binary
categorical variable with only two options
yes/no, true/false
quantitative discrete data
- integer values (whole values)
- values cannot be subdivided
of visits to a clinic, steps
quantitative continuous data
- data that can be measured on a continuum
- can be meaningfully subdivided
- length, mass
interval data:
- like ordinal but categories are a known factor
- ordered
- meaningful and equal differences between units
- no natural zero
- i.e. temperature
ratio data:
- ordered
- meaningful and equal differences between units
- has a natural zero
- i.e. height, mass, speed
measurement properties
- accuracy (how well measure shows true value)
- precision (how different multiple results of the same measure is)
- resolution
- linearity/hysteresis
- validity (how accurately a measure measure what it is intended to)
- reliability (reproducibility/ repeatability) i.e. if a study was repeated, would it yeild the same results?
accuracy
- how well a measure represents the true value
- defined as a ratio (the difference between the true value and the measured value divided by the true value)
precision
- the # of distinguishable alternatives from which the given result is selected
- high precision does not mean high accuracy
- precision is inversely related to standard deviation
resolution
the smallest incremental quantity that can be measured with certainty
- expresses the degree to which nearly equal values of a quantity can be discriminated
linearity/hysteresis
linearity: relationship between an input and output. the relationship remains the same over a wide range of input values
hysteresis: relationship between an input and output is affected by history of stretch, relaxation inputs
movement planes
- sagittal
- frontal
- transverse
kinematics
describes motion of a body without regard to the forces/torques that produce them
human body position is defined by:
- location
- orientation
- joint configuration
kinematic variables
- type of motion
- location of motion (what plane)
- direction of motion (flexion/extension)
- magnitude of motion
- rate of change of motion
translation
- doesn’t have an axis
- can be rectilinear (straight line) or curvalinear (curved path)
axis vs. plane
plane: 2D plane that movement occurs in
axis: rotation axis aligned perpendicular to the plane
degrees of freedom
- independent coordinates required to characterize a system, body, position
- number of independent directions of movement permitted at a joint
- max 6 DOF (3 rotation, 3 translation)
- there could be constraints that limit the degrees of freedom (joint structure, ligaments)
osteokinematics
refers to rigid body movement relative to the 3 planes of the body (sagittal, frontal, transverse)
open & closed kinematic chains
open: distal segment is free to move and the proximal segment is fixed
closed: distal segment is fixed and the proximal segment is free to move
arthrokinematics
- describes motion that occurs between articular surfaces (translations)
- if joints didn’t slide, they would bang into bones limiting ROM and impinged nerves
types of translations
roll:
multiple points of one articular surface comes into contact with multiple points of another surface
slide:
one point on a articular surface comes into contact with multiple points on another articular surface
spin:
a single point on one articular surface comes into contact with one point on another articular surface
convex-concave patterns
helps describe the roll and slide relationship that occurs between articulating surfaces
if the moving segment is convex, the osteokinematic movement and the arthrokinematic movement (gliding) are in opposite directions
if the moving segment is concave, the osteokinematic and arthrokinematic movements will be in the same direction
joint positions
closed packed:
- position of maximal joint congruency
- provides natural stability
loose packed:
- all other positions
- least congruent near mid-range
- least ligamentous stress on joint
3 key functions of a joint
1) movement
2) protection of internal structures
3) load tolerance/dissipation
how do joints produce movement, protect internal structures, and tolerate load?
1) passive osteoligamentous subsystem
2) active muscular subsystem
3) neural control subsystem
passive osteoligamentous subsystem
- not effective in the vicinity of neutral positions
- effectiveness increases as you approach close packed positions
- act as dynamic and active mechanoreceptors (transducers/sensors)
- detects changes in joint motion, deformation, acceleration through Ruffini endings and pacinian corpuscles
passive & active
considerations for the passive osteoligamentous subsystem
joint congruency: passive elements of the joint
- bone morphology (how the bones fit together)
- fibrocartilage discs (labrum, meniscus) and how these increase stability
ligamentous structures:
- # of ligaments
- size of ligaments
- arrangement of ligaments
- can act passively and actively
active muscular subsystem
- muscles generate force
- has mechanoreceptors (muscle spindles and GTOs) that send info to CNS based on muscle length and contraction rate (dynamic info)
neural control subsystem
- receives all info from transducers
- determines specific requirements for joint function
- causes active muscular subsystem to activate to achieve outcome
considerations of Panjabi’s Model
neural zone:
- zone of high flexibility/laxity where there is little internal resistance from passive osteolig. system
- represents the toe region of a stress-strain curve where no deformation occurs
- a smaller neutral zone makes the joint more stable
integumentary system:
- Panjabi’s model doesn’t consider skin and how burns and scars can impact joint movement
stability & mobility systems are not separate:
- movement functions as a continuum
- joint needs to be stable but not so stable that we can’t move
- muscles provide mobility and stability
- POL system provides stability but doesn’t directly contribute to mobility
intra-articular pressures:
- normal joints have negative pressure to provide stability
- when there is fluid in the joint, pressure increases above atmospheric and decreases stability
ligaments
- closest structures to joint
- plays biggest role in controlling movement
- contain type I collagen and elastin
4 primary types of tissue in the body
1) connective tissue
2) muscle
3) nerve
4) epithelium
connective tissue
contains:
- collagen (type I: ligaments, tendons and type II: hyaline cartilage)
- elastin
viscoelasticity
physical properties of the stress strain curve change as a function of time
most musculoskeletal tissues have some viscoelasticity
creep, hysteresis, tension-relaxation
what properties do viscoelastic structures have?
- creep
- hysteresis
- tension-relaxation
stress-strain curve
non-linear relationship between length and tension
toe region:
- crimp in toe region is starting to straighten
- small increase in stress for large strain
linear region:
- crimp from collagen is completely gone
- sharp increase in tension with still relatively small strain
partial failture region:
- microfailure where collagen fibres start to break
total failure:
- where ligament snaps
slop of curve shows how easily a tissue deforms (larger slope = less deformation)
toughness is the area under the slope
creep - constant load
- when constant load is applied to a ligament over a prolonged period of time, it will continue to elongate over time to a finite maximum
- ligament does not immediately go back to original length meaning the crimp has not returned to the fibres (residual creep)
creep - constant length (tension-relaxation)
- tension in a ligament increases immediately upon elongation
- over time the tension decreases without change in length
- means there is less tension needed to hold the ligament to that length
- ligament relaxes over time because crimp is coming out of the collagen fibres
hysteresis
- ligaments inability to track the same length-tension curve when subject to repetitive stretching or loading
- repeatedly elongating a ligament to a constant length causing tension to decrease or repeatedly applying a load to a ligament causing length to increase
risks of hysteresis
- increased joint laxity
- decreased joint stability
- increased risk of injury
mechanoreceptors in ligaments
pacinian corpuscles:
- sensitive to small changes in deformation
- activated only at the beginning or end of stimulus or during acceleration/deceleration
- fast acting
Ruffini endings:
- slow-adapting mechanoreceptors
- send info that stress is continuing
- detects static and dynamic factors
what are risk factors for altered viscoelastic response in ligaments?
- cyclic loading at high frequencies
- long work durations
- short rest periods
- high # of reps
- static or cyclic work with heavy loads
definition of newborn, infant, child, adolescent
newborn: 1-28 days
infant: up to 12 months
child: 1-10 years
adolescent: 10-19 years
how many bones does a newborn have
~300 that fuse in 206
osteopenia
decreased bone density (pre-term <37 weeks)
bone modelling
process where bones change their overall size and shape in response to forces
occurs in first 2 decades
factors impacting bone modelling
1) compression/tension forces - stimulates bone lengthening (caused by weight bearing and muscle pulls)
2) shear forces - stimulates torsional change (caused by muscle pulls)
bone remodelling
process where bone is renewed to maintain strength and mineral homeostasis
reabsorbs old bone (osteoclasts) and lays new bone (osteoblasts) to prevent accumulation of bone microdamage
hip joint development
- 12 week fetus has deep acetabulum
- new born has more shallow acetabulum
foot development
- infants are born with pes planus (flexible flat foot)
- at birth a fat pad is present in medial aspect of foot to support the arch
- development of medial longitudinal arch occurs between 2-6 years
- flexible pes planus is normal for children under 8
metatarsus adductus & tibial torsion
- metatarsals deviated inward
- common
- usually resolves on its own
clubfoot
one or both feet twisted in abnormal position
congenital muscular torticollis
poor positioning in utero causes a short SCM
brachycephly and scaphocephly
back lying too much cause flat back of skull
and
side lying too much causing narrow skull
arthrogryposis multiplex congenita
- non-progressive neuromuscular syndrome at birth
- severe joint contractures and muscle weakness
osteogenesis imperfecta (brittle bone disease)
- inherited disorder of connective tissue
rickets
defective mineralization or calcification of bones due to deficiency or impaired metabolism of vitamin D or calcium
cerebral palsy
- movement and posture disorder causing limitations
- caused by lack of O2 during birth or stroke in utero
label sarcomere graph
I-band: contains z-disc and actin. gets smaller during contraction
Z-disc: sarcomere boundary that holds actin in place. gets pulled closer to middle during contraction
A-band: contains actin and myosin. no change in length during contraction
H-zone: central region of sarcomere containing only myosin. gets smaller during contraction. contains M-band
how does muscle activation occur?
- impulse reaches neuromuscular junction
- ACh is released and crosses NMJ and binds to receptors causing action potential to travel down muscle fibre
- goes down transverse tubule which opens Ca+ releasing channels and Ca+ goes into the fibre
- Ca+ causes troponin to move off myosin binding sites on actin
- myosin heads bind to actin causing a powerstroke, pulling actin in
- Ca+ is pumped out of the fibre and myosin binding sites are covered again
- muscles relaxes
functions of passive tissues in muscles
1) serves as scaffolding and holds muscle fibres together
2) conduit for blood vessels and nerves
3) conveys part of contractile force to the tendon
4) resists passive stretching and ensures forces are distributed to minimize damage to muscle
types of connective tissues in muscles
- epimysium
- perimysium
- endomysium
critical length
where passive structures start to feel tension. if you increase flexibility, the critical length will shift to the right
alpha motor nerves
- innervate skeletal muscle and cause contractions
- release acetylcholine at the neuromuscular junction
motor unit
alpha motor nerve and the muscle fibres that it innervates
recruitment of motor units
1) spatial recruitment
2) temporal recruitment
where do alpha motor and sensory neurons comes from?
alpha motor neurons - ventral horn of spinal column
sensory - come into dorsal horn of spinal column
spatial recruitment
- Henneman size principle
- smaller motor units with smaller innervation ratios are recruited first and then larger motor units are recruited as more force is needed
- type 1 oxidative are recruited first (slow twitch and most fatigue resistant), then type 2 oxidative (fast twitch but more fatigue resistant), and then type 2 glycolytic (fast twitch and fatigue quickly)
how is force production modulated?
spatial and temporal recruitment of motor units
temporal recruitment
- rate coding
- can change the rate of recruitment of motor units
tetanization: when action potentials fire so fast the line on a graph smooths because the rate of motor unit stimulation is so high
this can be seen in neuromuscular electrical stimulation when muscle twitches at first and then stops as rate of motor unit firing increases and reaches tetanization
electromechanical delay
delay between onset of muscle stimulation by the alpha motor neuron and the development of torque at the joint
30-100ms
muscle receptors
motor neuron recruitment and rate coding depend on information sent to CNS from:
- muscle spindles
- golgi tendon organs
- free nerve endings
all within the muscle
muscle spindles
- intrafusal fibres that consist of nuclear bag and chain fibres
- density of muscle spindles varies between muscles (need more proprioceptive info in neck than arm)
- sensitive to rate of stretch and length
golgi tendon organs
- located in musculotendinous junction
- only has sensory nerves
- detects muscle contraction
- inhibits motor neurons
physiological cross sectional area
- area perpendicular to muscle fibres
- > cross sectional area = more cross bridges formed = more force
- total force is proportional to physiological cross sectional area
muscle force = total force x cos theta
scalar vs. vector quantities
scalar: represented by magnitude (mass, time, length)
vector: represented by magnitude, orientation, and point of application
equation for calculation question
Cos⍬ = BC . BA / |BC| x |BA|
. = dot product
stability
ability of a system to remain within a boundary of control after a perturbation is applied
bone development time lines
upper limbs & scapulae: 17-20 years
lower limbs & coxae: 16-23 years
sternum, clavicles, vertebrae: 21-25 years
what is the final size of skeletal muscle fibres dependent on?
- blood supply
- innervation
- nutrition
- gender
- genetics
- exercise
what force causes growth of muscle tissue?
tension
joint development
basic joint structure is formed by 6-8 weeks gestation
final shape is dependent on forces of movement and compression during early childhood
what do breach babies have a increased risk of?
developmental dysplasia of the hip
more common in females
typical skeletal changes with development
varus angulation (bow leg) -> valgus angulation (knock-knees) -> varus (again in later life as osteoarthritis
atypical pressure on hip during development
obesity: can cause slipped capital femoral epiphysis (unstable hip joint)
spasticity: causes asymmetrical pull of the joint increasing the risk for subluxation and dislocation
