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PT 5133 Kinesiology Northeastern University

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Northeastern University

PT 5133 Kinesiology Northeastern University

Kinesiology Quiz 1 Study Guide
 Coordinates- a reference system to help define direction and magnitude
o Clinical coordinates- joint motion is described using clinical coordinates
unless otherwise specified
 Origin- an arbitrary point on the body when the body is in
anatomical position
 X, Y, and Z axes
o Global coordinates
o Relative/Local coordinates
 Sagittal plane:
o Medial/lateral axis penetrates the sagittal plane (motion occurs around
 Cuts the body into left and right halves, looking at body from the
o Joint motions in sagittal plane:
 Ankle- dorsiflexion/plantarflexion
 Shoulder- flexion/extension
 Hip- flexion/extension
 Frontal plane:
o Anterior-posterior axis penetrates frontal plane (motion occurs around
 Cuts the body into front and back halves, looking at the body from
the front
o Joint motions in frontal plane:
 Cervical- lateral flexion
 Shoulder- ABD/ADD
 Wrist- radial/ulnar deviation
 Ankle- INV/EV (occurs at subtalar joint)
 Transverse plane:
o Vertical axis penetrates the transverse plane (motion occurs around axis)
 Cuts the body into upper and lower halves, looking at the body
from the top
o Joint motions in transverse plane:
 Cervical- rotation
 Shoulder- IR/ER
 Ankle- ADD/ABD
 Osteokinematics- a study of the movement of a bone with relation to the other
o Joint range of motion
o Position- the location of a body component
o Motion- the movement of a body component
 The act of the body part moving from one position to another
 Open chain- the distal bone moves freely while the proximal bone is fixed
 Closed chain- the distal bone is fixed while the proximal bone moves freely
 Arthrokinematics- study of the movement of the articular surfaces
o Articular surfaces can:
 Spin- a single point of a moving object rotates on a single point of a
stationary object
 Ex: radial head spinning on humeral capitulum during
 Glide (slide)- a single point on the moving object contacts multiple
points on the stationary object
 Roll- multiple points on the moving object contact multiple points
on the stationary object
o In joints with concave-convex configuration both limbs roll and slide
 Concave-Convex rule:
 Concave moving on convex: concave segment rolls and
glides in same direction
 Convex moving on concave: convex segment rolls and
glides in opposite directions
 Choose the moving segment, select a point, look at where the point
would move
 Kinematics- a study of position and position change without considering the
cause of the position change
o Isometric- muscle is working but not moving
o Concentrically- muscle is working/shortening
o Eccentrically- muscle is working/lengthening
o If gravity can help the agonist is not going to work in order to save energy
 Antagonist works eccentrically
o When gravity is not helping, agonist works concentrically
o Primary mover is the muscle that works the most
o Co-contraction stabilizes the joint: both antagonist and agonist must
work in order to maintain a position
Biomechanics 1
 Forces:
o Internal force- generated by muscle
o External force- generated by gravity
o Torque- angular force
 Newton’s laws- basis of musculoskeletal biomechanics
o Law of inertia- an object at rest tends to stay at rest and an object in
motion tends to stay in motion, unless there is a force changing its
current status
 Inertia- the ability of an object to resist change
 The greater the mass, the greater the inertia
 Whiplash- body moves forward, head stays in same
position  hyperextension torque of cervical spine,
damages to soft tissue structures (deep neck flexors,
anterior longitudinal ligament, etc.)
 Moment of inertia- ability of an object to resistant change in an
angular movement
 Moment of inertia- angular term
 Inertia- linear term
 I = mr ^ 2
o I = moment of inertia
o M = mass
o R = radius of rotation
o Law of acceleration: F = ma
o Law of Action-Reaction: for every action there is always an equal and
opposite reaction
 Ground reaction force- when you apply a force to the ground, the
ground will generate a reaction force to you
 The ground reaction force is equal in magnitude and
opposite in direction to the force that the body exerts on
the ground
 Analysis of force
o Movements results from interaction of internal and external forces
o To perform force analysis you need to have basis knowledge of:
 Coordinate- global and relative/local
 Global coordinate- describes a position in relation to the
o Origin- an arbitrary point in the space defined as
o X- represents the AP direction of the space (parallel
to the floor)
o Y- represents the vertical direction of the space
(perpendicular to the floor)
 Relative/local coordinate- describes a position of a segment
in relation to the adjacent segment
o Coordinate system changes depending on your
o X is parallel to the body segment that is moving
o Y is perpendicular to the X
 Features of force:
 Force has an application point
o Muscle force- the attachment of the muscle to the
o Gravity- the center of mass of the body segment
 When standing, center of mass is at S2
 Force has a magnitude
o Muscle force- biceps produce N
o Gravity- weight of the forearm
 Force has a direction: changes depending on coordinate
o Global coordinates- muscle force is moving upwards
in the vertical direction
o Relative coordinates- muscle force has an angle of
pull so it’s difficult to describe direction
o Vectors have both direction and magnitude (force,
o Scalar has only magnitude, no direction (mass,
 Force decomposition:
 When force is neither parallel to the X axis nor parallel to
the Y, it can be decomposed into an X component and Y
o The resultant force, the X component, and the Y
component all have the same application point.
 X component will be parallel to x-axis
 Y component will be parallel to y-axis
 The resultant force, the X component, and the Y component
can form a right triangle (with simple shifting)
o Hypotenuse = resultant force
o Adjacent = x component
o Opposite = y component
o COS= A/H
o SIN = O/H
o Applying force to a body segment can make the segment rotate about its
 Joint is an axis of rotation, rotation is a joint movement
 Not always true, rotation is not just about force but also about
moment arm. If there is no moment arm there will be no rotation.
 Torque = force * moment arm
o To make a segment move about the joint, we need both force and moment
 Torque is the angular term for force
o Moment arm = the perpendicular distance from the axis of rotation to the
force vector
 You might need to extend the force vector
 When force penetrates the axis of rotation, there is no moment
arm  no rotation
 Simple joint movement analysis:
o Application point = distal attachment of muscle
o Acceleration due to gravity = -9.8
o If net torque is negative (downwards), the exercise would be too difficult
for the client.
Biomechanics 2:
 Levers:
o A lever system is formed by forces, axis of rotation, and moment arm
o 3 types of levers in our body:
 First class lever- axis of rotation is in the middle and resistance
and effort are on the two sides
 Ex: AO Joint
 Application point: center of mass
 Second class lever- resistance is in between the axis of rotation
and the effort
 Mechanical advantage- helps us save energy or effect
o Moment arm for effort is larger than the moment
arm of resistance
 Ex: calf muscles when plantar flexing
o Ball of foot is axis of rotation
o Plantarflexors are effort
o Resistance is in the middle
 Third class lever- effort is located between the axis of rotation and
 Most commonly observed in the body
 Excursion advantage- we can get the job done with shorter
distance of traveling
o Effort is near the axis of rotation so you don’t need
to travel much for the action to happen but it
requires more force
o Moment arm for effort is shorter than moment arm
for resistance (no mechanical advantage)
 Ex: elbow flexors
o Elbow joint is axis of rotation
o Elbow flexors are effort
o Weight in hand is resistance
 Momentum = mass * velocity
o Anything that is moving has momentum. Check the velocity to know if
something is moving.
o Transfer of momentum: momentum can transfer from one object to
 Intersegmental dynamics- transfer of momentum
 When you move the femur, the pelvis moves
 When you move the arm, the shoulder moves
 This is why stabilization of joints is so important
o To stop momentum of an object, you need to apply a force to the object
over a period of time. In other words, you need to generate impulse
 Impulse = force * time
 Mass*acceleration*time = force * time = impulse
o Impulse can be used to both generate and break momentum
 Work (J) = force * displacement (S)
o S = terminal position – initial position
o Work occurs when a force causes an object to move
o Muscle work: can be positive, negative, or absent
 Positive work:
 Ex: elbow flexors generate force and the elbow is flexing
 Concentric contractions
 Generating energy
 Negative work:
 Ex: elbow flexors are generating force, but the elbow is
 Eccentric contractions
 Absorbing energy
 No work:
 Ex: elbow flexors are generating force but the elbow is not
moving at all
 Isometric contraction
 Energy (scalar) is the capability for the system to do work. There are two types
of mechanical energy:
o Potential energy
 Energy due to its position
 M*g*h
 M = mass
 G = gravity constant
 H= height
 Stored energy
 Once potential energy is released it can do certain work
 It does not do work if it’s stored
o Kinetic energy
 Energy due to motion
 ½(m/v^2)
o Energy can never be destroyed: potential energy + kinetic energy =
 Kinetic and potential energy values may change (inversely related)
but the total mechanical energy is constant
o Loss of potential energy transforms to kinetic energy to get the work
 Power (Watts) = work/time
o Positive relationship with work
o Negative relationship with time
o Rate at which the work is done
o Power = work / t = F*S / t = F * V
Kinesiology Quiz 2 Study Guide
 Joint Surfaces: far more stable than shoulder
o Acetabulum: junction of pelvic bones
 Faces anteriorly, laterally, and inferiorly
 Articular surface is horseshoe shaped
 Acetabulum is filled with fat and ligamentum teres
 Requires weight bearing to develop
o Femur: longest, strongest bone in the body
 Slight anterior/posterior bowing allows: slight flexion in weight bearing, high
compression loads, compression posterior and tension anterior
 Femoral head: 2/3 of the sphere is covered with articular cartilage
 But not the fovea (center point)
 Angles of inclination and angle of torsion- you can’t change these angles but it
will help you determine what a patient is predisposed to or what can be
contributing to their problems that you can fix.
 Angle of inclination: frontal plane neck to shaft angle
o Normal: 125º but 140º-150º at birth
o Coxa valga: > 125º
 Seen in DDH, Spina Bifida, NWB CP
 Causes varus at the knees (compensation to stay in
 Abduction at hips with weight bearing to maximize joint
o Coxa vara: < 125º
 Seen with slipped capital femoral epiphysis
 Causes valgus at the knees (compensation to stay in
 Adduction at hips with weight bearing to maximize joint
 Angle of Torsion (anteversion): transverse plane “twist”
o Normal: 10º-15º but 35º at birth
o Excessive anteversion: >15º
 Toes in as compensation to stabilize hip/maximize joint
congruency with weight bearing (a lot of hip IR)
o Retroversion: <15º
 Toes out as compensation to stabilize hip/maximize joint
congruency with weight bearing (a lot of hip ER)
 Trabecular systems- gives stability and strength to head of the bone; mesh bone
in the proximal femur (area for signs of osteoporosis/osteopenia) that is aligned
to transfer forces:
 Wolff’s Law: the line of pull of the soft tissues (ligaments and muscles)
created good calcification and a strong bone
 Functional Hip PROM:
o Walking:
 Sagittal plane: 40º (F/E)
 Frontal plane: 12º (ABD/ADD)
 Transverse plane: 12º (IR/ER)
o Ascending Stairs: requires more mobility than walking, descending stairs
 Sagittal plane: 67º (F/E)
 Frontal plane: 16º (ABD/ADD)
 Transverse plane: 18º (IR/ER)
o Descending Stairs:
 Sagittal plane: 36º (F/E)
o Tying shoe with foot on floor: bending down to tie shoe (requires more hip mobility)
 Sagittal: 124º (F/E)
 Frontal Plane: 19º (ABD/ADD)
 Transverse Plane: 15º (IR/ER)
o Tying shoe with foot on opposite thigh:
 Sagittal Plane: 110º (F/E)
 Frontal Plane: 23º (ABD/ADD)
 Transverse Plane: 33º (IR/ER)
o Sit to Stand:
 Sagittal Plane: 104º (F/E)
 Frontal Plane: 20º (ABD/ADD)
 Transverse Plane: 17º (IR/ER)
 Arthrokinematics:
o Femoral Head is a convex mover in the concave acetabulum
o ABD: rolls superior, glides inferior
o ADD: rolls inferior, glides superior
o Flex: rolls anterior, glides posterior
o Ext: rolls posterior, glides anterior
o IR: rolls anterior, glides posterior
o ER: posterior, glides anterior
o Close Packed Position: Max extension with max IR
o Loose Packed Position: 30º of flexion with 30º ABD and slight ER
 Position for mobilization—joint is relaxed so you can move things
o Dislocation: rare overall but after THR posterior/inferior dislocations may occur
because posterior capsule is damaged in surgery
 Stability
o The hip has a deep socket with significant joint surface congruency
o Tight, strong ligaments and capsule contribute to stability:
 Iliofemoral “Y” ligament- limits extension
 Paraplegics posture- patients are taught to stand in close packed position
at the hips so they are essentially hanging on the Y ligament. It doesn’t
take a lot of effort for them to stand this way (not a lot of effort of muscles
o In a healthy person, not a good posture
 Ischiofemoral ligament- limits IR, Ext and Add
 Pubofemoral ligament- limits ABD and extension
 Weight bearing and NWB motions:
 In NWB—open chain (ex: pt lying on table)
 When you flex hip femur moves (glides) posteriorly in joint
 When you extend, femur glides anteriorly in joint
 ABD- inferior glide
 ADD- superior glide (more functional than in shoulder, need 15º)
 ER- anterior glide
 IR- posterior
 In weight bearing—closed chain (ex: sitting or standing)
 Acetabulum becomes mover (concave)—rolls on femur
 Ex: ADD hips- superior glide of femur but inferior motion of acetabulum,
IR- posterior glide of femur
 Forces
o Frontal Plane- When standing, ground reaction forces and muscle forces need to cancel
each other out or you would fall down
 More you load, more muscle force necessary to keep static equilibrium (net force
= 0)
 Ex: add backpack on, need more muscle force
 Trendelenburg Test- have patient stand on one leg and see if hips stay level
o They must be at least a three to do this so it is also an MMT functional test
o Positive test  functional weakness of glute med (less than a 3)
 Force Couples: pairs of muscles working together
o Always happening on pelvis/lower extremity to cause normal movement of pelvis
(rotation/direction of motion)
o Most common issue: anterior pelvic tilt (hip held in flexion)
 Tight rectus femoris, tight iliopsoas  pull pelvis down


PT 5133 Kinesiology Northeastern University

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