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62nd Sem: Movement Science > Exam 1 > Flashcards

Flashcards in Exam 1 Deck (218):

What is biomechanics

Study of movement in living organisms


Define each:

- Statics:
- Dynamics:
- Kinematics:
- Kinetics:

Examples of Kinematics vs. Kinetics movements:

- Statics: It's static or not moving
- Dynamics: MOVING. Something in motion
- Kinematics: Study of movement WITHOUT consideration of forces involved.
- Kinetics: Study of movements WITH forces involved.

Kinematics: displacement, position, velocity, time
Kinetics: torque, gravity, friction


Explain the different types of motion:

- Translatory:
- Rotary:
- Curvilinear:

- Translatory: all points on a segment travel in a parallel line (whole bar moves, and all points on bar move together the same).

- Rotary: a segment travels around an axis of rotation (whole bar moves, but different points on bar move at different lengths and speeds)

- Curvilinear: A combination of translatory and rotary motions


As humans, do we usually have translatory, rotary, or curvilinear movements?

Example of curvilinear?

Some rotary, some translatory, but mainly CURVILINEAR

Someone running (or car driving) around the rounded corners of a racetrack.



If someone is doing flexion / extension, name the PLANE and AXIS they are working in?

If someone is doing abduction / adduction, name the PLANE and AXIS they are working in?

If someone is doing rotation, name the PLANE and AXIS they are working in?

Flexion/Extension: Sagittal plane about a frontal (or horizontal) axis

Abduction/Adduction: Frontal plane about sagittal axis

Rotation: Transverse/Axial plane about a vertical axis


Imagine the xyz hand motion. Explain direction of x, y, and z, direction, and finger used for the GLOBAL and REGIONAL / LOCAL system.

Which is positive direction, which is negative?

What should Y be?
What should X be?

y = superior to inferior (index finger)
x = medial to lateral (thumb)
z = anterior to posterior (middle finger)

Choose Y to be sup/inferior, and then choose X to be ant/posterior (but really you can choose x or z to be any plane you want in a local).

Positive directions (positive x, y, z) are Y points up / Superior, and then x and z are positive in whatever direction they point. An object moving DOWN is a negative Y direction.

Y = vertical up and down direction
X = direction of the force


Flexion and extension are in what plane?

Ab/Adduction are in what plane?

Rotation is in what plane?


Frontal / Coronal

Transverse / Axial


*** KNOW

1 Degree = ??? radians
1 Radian = ??? degrees

1 Meter = ? centimeters (cm)
1 Meter = ? millimeters (mm)
1 cm = ? mm
1 Meter = ? inches
1 cm = ? inches
1 inch = ? cm

1 Kg = ? gm
1 Kg = ? lb
1 lb = ? Kg

1 Degree = 0.017 Radians
1 Radian = 57.3 Degrees

1 Meter = 100 centimeters (cm)
1 Meter = 1000 millimeters (mm)
1 cm = 10 mm
1 Meter = 39.4 inches
1 cm = 0.394 inches
1 inch = 2.54 cm

1 Kg = 1000 gm
1 Kg = 2.2 lb
1 lb = 0.45 Kg


Difference between mass and weight

Gravity = ?

Mass: Amount of matter

Weight: force of gravity acting on mass/object

9.8 m/s^2


Summarize Newton's 3 Laws:

1st Law: Law of Inertia (an object will stay in motion / rest unless acted upon by another force)

2nd Law: F=ma (force = mass x acceleration)

3rd Law: For every action (force) there is an equal and opposite reaction (force) in the opposite direction (push a wall, it pushes back)


Define these kinematics principles:


Explain difference between speed, velocity and acceleration

Position - the location of a point or object in space.

Displacement - the distance traveled between two locations.

Velocity – the speed of something in a certain direction

Acceleration – the changes in linear and angular velocity over time.

Average speed is distance divided by time. Velocity is speed in a given direction. Acceleration is change in velocity divided by time.


Units for:


Displacement: meter (m) (in body we use cm)
Time: second (s)
Speed: mph or m/s
Velocity: m/s
Acceleration: m/s^2
Momentum: kg * m/s
Mass: kg or lbs
Force: N (lb and kg in this class) ... (kg*m/s^2)


What is inertia?

What is moment of inertia?

Remember the youtube video of the dad with his two girls ... what was that example?

Formula for Inertia: (what does it mean??)

Would you spin faster or slower with arms in / mass in?

Why do you bring your arms in/up when you run?

Inertia: resistance to an object moving

Moment of Inertia: Rotational acceleration ... measure of resistance to angular acceleration

You put the mass at the ends of the sticks and hold stick in the middle, it is HARD to rotate. Put mass (weights) in at the center, and you can rotate a lot easier.

I = mr2 (m =mass, r =distance from COR). So if I decrease mass or distance, I decrease inertia / resistance.

Faster, cause I=mr^2 and I'd have less resistance if I decrease r. (Figure skater can spin faster with arms in)

Doing this helps during running to go faster. Brings mass closer to axis of rotation.


Define each, and give formula:

Energy (2 kinds)

Work - the force required to move an object a certain distance (work = force x distance)

Power - the rate that work is being done (power = work / time)

Energy of a system refers to its capacity to perform work
1) Potential Energy - stored energy
2) Kinetic Energy - the energy of motion


What are the two coordinate systems (and examples):

GLOBAL: How an object moves with respect to the surrounding environment. Ex: person walking around a room, or whole body.

LOCAL: How an object moves with respect to another closely related object. Ex: flex or extend elbow around a joint, or a segment compared to another segment..


Review Soh Cah Toa

T or F: only works with RIGHT triangles?

Another way to find the size of a side with a right triangle?

Sin = opposite / hypotenuse
Cos = adjacent / hypotenuse
Tan = opposite / adjacent


Pathagorum theroum: a^2 + b^2 = c^2


Muscles PUSH or PULL?

Ligaments PUSH or PULL?

Bones PUSH or PULL?

You can't _______ a rope.

Muscles Pull.

Ligaments Pull.

Bones PUSH.

You can't PUSH a rope.


A muscle is a VECTOR QUANTITY. That means it has 4 things:

- Magnitude (force)
- Orientation (angle)
- Direction (direction)
- Point of application (axis or starting point)


What is each force below, and an example:

- Resultant force:
- Orthogonal force:

Mathmatically, how would you draw the resultant force of 2 forces at a right angle?

- Resultant force: one force which is the result of multiple forces acting. Example: 2 heads of biceps contract (2 forces) and resultant force is pulling radius up.

- Orthogonal force: Two forces acting at right angles to each other ... to produce a resultant force.

- You put the tail of one force at the head of the other force, complete a right triangle and that hypotenuse is the resultant force.


1) What is a Force System:

2) What is a Free Body Diagram?

3) All the forces in a free body diagram is a ______ ________

4) 3 types of force systems?

5) 4 types of forces that can act on a force system (and examples):

1) A force system is a collection of forces acting at specified locations (within a system).

2) Free body diagram is a quick drawing listing each of the forces acting in the problem/situation.

3) Force system ... a group of forces.

- Linear (straight line)
- Planar (a specific plane)
- Space (area combining more than one plane)

4 types:
- Collinear: forces acting along the same straight line

- Parallel: forces acting parallel to each other (Dr. T applied a parallel force to shoulder on me of the same force of shoulder ligaments)

- Concurrent: forces that intersect at a common point (brace on ankle / knee … apply forces around a joint)

- General: forces that are not collinear, parallel or concurrent but still act within the area or upon the body (any other force outside those 3 above)


We know we can add two vectors together to get a resultant force. How?

But can we subtract vectors (give example of deltoid muscle)?

Put tail of one vector at head of other vector (all in same orientation as they originally were). Then draw hypotenuse and that is resultant vector/force. The two other vectors are the orthogonal vectors.

If anterior and posterior portion of deltoid muscle worked, you'd add the two up, and resultant force would create straight up abduction of shoulder. But, if anterior portion got injured / nerve damage, then only posterior portion would work, so you minus the anterior portion, and resultant force is the direction of the posterior force.

SO, you take RESULTANT force, then switch direction of anterior (put new tail on head of resultant) and then draw new hypotenuse (it just so happens it is the posterior force).


Example of a joint compression force

Example of a joint tension force

Example of a shear force?

As a PT, when and why would you use compression vs. tension on a patient?

Compression: lying prone, shank flexed to compress tibia on femur. Or carrying a really heavy box adds compression force of femur on tibia (or lumbar spine).

Tension: sitting on plynth with leg bent over table, hanging (tension on lig's) ... and especially with weight on the ankle. Or PT pulling joint apart (joint play).

Shear: Rotation

If patient torn a ligament, do compression. If patient has arthritis or articular cartilage / meniscus damage, do tension.


Examples of types of forces:

(weight and mass are used interchangeably)

Muscle tension

Ground reaction force (GRF)
You stomp on ground, and ground stomps back. Equal and opposite force.

Normal force
Perpendicular to surface. You push down on table top. Computer pushes down on table. But if object is on a slope, weight/gravity goes to center of earth and normal force is perpendicular to surface.

Force of gravity
It always pulls toward center of the earth


Push/Pull force

External force applied by someone else


What is center of gravity:

Two examples of center of gravity:

COG = the hypothetical center of mass at which the force of gravity appears to act

1) Overall: Example of baseball bat and how there is a point it can balance because weight on each side is equally distributed.

2) Segmental: Each segment of the whole has it's own COG (a limb has it's own COG)


COG for each plane in human body in each plane:


T or F: each body segment has it's own COG

Frontal: S2
Transverse: Anterior of sacrum
Sagittal: Midline



T or F: line of gravity has to fall between the base of support in order for you to be able to stand up?

What is H.A.T.

How do you change base of support for more stability?

What will a cane do to base of support and COG?

Why is walking on crutches so dangerous?

True (although, if you get off balance, obviously your muscles help compensate to ensure you don't fall over).

HAT = Head, Arms, Trunk (ignores LE)

Widening your stance

A cane will widen base of support, and thus shift COG out and to the right (towards cane)

With crutches on ground, you have a triangle and wide base of support. But as soon as you remove crutches from ground, it is just the one foot that is the base of support, which limits it significantly. And COG swings outside base of support if you do a "step through."


What would be easier to knock over ... a tall object with COM/COG in middle of object, or a tall object with COM/COG down close to base of support?

Why do tight ropers use large pole?

The closer the COM/COG is to the base of support, the more stable it will be.

Keeps line of gravity close to base of support, so you can't fall as easily.


What might alter someone's base of support or COG/COM in their body?

- Gender differences
- Hypertrophy/atrophy
- Amputations (prosthetic)
- Huge brace
- Cane or assistive device
- Being pregnant
- Holding heavy bag on one side
- Adding an external load (big back pack)


Explain the components of a lever (in anatomy):

- Lever arm / rigid bar:
- Fulcrum/Axis:
- Force:
- Resistance:

What is a lever arm?

- Lever arm / rigid bar: body segment / limb
- Fulcrum/Axis: JOINT
- Force: Muscle contraction
- Resistance: Externally applied force (or gravity)

The lever arm is defined as the perpendicular distance from the axis of rotation to the line of action of the force.


What is the perpendicular distance =

Distance from joint (AOR) to the force. It is perpendicular to the direction of the force.


What are the 3 classes of levers:

How to remember?

F = force
A = axis
R = resistence (gravity, weight of bone, PT applying force)

1st Class: FAR

2nd Class: ARF

3rd Class: AFR

Remember: Throw the bone FAR, dog fetches it and says ARF. Comes back after (AFR).


One of the LEAST used levers in body is:

Most common used levers in body?




Name what type of lever this action would use:

Plantar flexion / Heel raise
Flex Elbow
Extend Elbow
Nod yes (atlanto-occipital jt)

Dorsiflexion: 3rd (AFR)
Plantar flexion / Heel Raise: 2nd (ARF)
Flex Elbow: 3rd (AFR)
Extend Elbow: 1st (FAR)
Nod yes (atlanto-occipital jt): 1st (FAR)


Would a longer lever arm give you more or less torque? WHY?


T = F┴d


Df means
Dr means

If Df is longer than Dr, will force or resistance be stronger or easier to do?

This is called:

Distance from axis to the force
Distance from axis to the resistance


MECHANICAL ADVANTAGE (or how much easier does the "machine" make the work).


What is torque

Formula for torque =

┴ =
┴d =

Torque goes clockwise or counter-clockwise. Which one is POSITIVE direction?

And is positive torque indicated by an UPWARD arrow or DOWNWARD arrow?

Is weight a force?

Force applied through a lever causing rotation around AOR. Force is straight force, torque is rotation movement created around an axis.

T = Force x perpendicular distance (T = F x ┴d) ................. or T = weight x ┴d

┴ = perpendicular
┴d = perpendicular distance from AOR to force

*** POSITIVE direction is actually COUNTER-CLOCKWISE

Upward arrow.

Yes, weight is a force since it is mass x gravity.


Using the RIGHT HAND RULE with regards to torque, what does thumb represent, what do fingers represent?

Thumb is Z axis, fingers are direction of torque


What is a force couple

Examples in body ... and in life?

If you have more than one force and torque acting on same lever, but the forces are PARALLEL and in OPPOSITE directions on each end of the same lever. That is a FORCE COUPLE. It helps create rotational movement.

Examples: Shoulder and hip in body ... steering wheel in car


In a body, what is a:

Axis of rotation:
Lever Arm:

Resistance: Gravity and weight of limb (or external force)
Lever Arm: Limb
Force: Muscle


Review slide 24 of 1B power point.

T or F: If the force weight and distances from AOR are different on both sides, but their torque is equal and opposite directions, if they both equal each other, will there be movement?

But what if the equal torques on different sides are going in the SAME direction, will there be movement?

No. It will be equilibrium.

Yes ... like a steering wheel.


If force = 10kg and it is 15cm from the AOR, what is the torque?



T or F: The body is full of pulleys

Give examples of pulleys in body

2 types of pulleys (define and give examples)


Patella is a pulley for line of pull of quads tendon, elbow, shoulder, fingers

Fixed Pulleys: Pulley does not move. Force is just changed DIRECTIONS, the magnitude doesn't change. Ex: Forearm muscle bellies pull long tendon (pulley rope) to move fingers.

Moveable Pulleys: Pulley moves, and distributes weight (shares the load). So now a 5kg weight is distributed to 2.5kg each on two sides of rope.


Define each:

- Load:
- Total Load:
- Unit Load:

Example: Assume that a load of 10 Kg is applied normal to a horizontal surface measuring 5 cm2. You may also assume that the load is distributed evenly over the horizontal surface.

Now, what is load, total load, unit load:

- Load: force applied on a structure
- Total Load: sum of all forces
- Unit Load: force per unit of area (how much force p/cm)

- Load: 10kg
- Total load: 10kg/5cm^2
- Unit Load: 2kg/cm^2


In measurments in the human body, would we use meters or cm?

CM (meters is too big)


What is stress:

Symbol for stress:

3 types of stress (explain and give examples):

How would you see these 3 stresses in the knee?

The resistance in a substance to physical deformation by external forces


3 types:
- Tension: Resisting being stretched / elongating (tendon or ligament)
- Compression: forces pushing together / shortening (bones)
- Shear: sliding / friction back and forth (joint surfaces)

In the Knee:
- Tension: MCL holding bones together being stretched
- Compression: Tibia and femur smashing into meniscus and being pressed
- Shear: top of tibia sliding on femoral condyles


What is strain:

Symbol for strain:

3 types of strain:

The actual physical deformation from stress (this class causes stress, and my face shows the strain)


3 types (same as above):
- Tension: elongation
- Compression: shortening
- Shear: sliding


What is Young's Modulus:

Formula for Young's Modulus:

What will deform more under stress (pressure): bone or muscle

When you add more and more and more stress on each of these below, which will move the least, which will move the most? Rank them from move (deform most) to deform least.

- Muscle
- Bone
- Tendon
- Cartilage

Muscle has an E of 6, and bone has an E of 140,000. What does that mean?

Is the E of a long bone bigger longitudinally or transversely?

Measure of a material's stiffness

E = stress / strain ... (E = σ / ε) .... ratio of stress or force / strain or deformation


- Muscle
- Cartilage
- Tendon
- Bone

Means that bone is MUCH more stiff, and can handle a lot more stress (resistance) than muscles without deforming (strain). It takes a lot more stress to deform (strain) a bone than it does a muscle.

Longitudinally (remember the longitudinal box, 30 degree angle box, 60 degree angle box, and transverse box. Longitudinal is much stronger than transverse).


What is Hooke's law?

What is hookian and non-hookian deformation?

For each additional unit of stress added, you get more strain (and visa versa)

Hookian is each unit of stress adds another unit of strain in equal proportions (straight line). It is proportional.

Non-hookian is a material that the more stress you add, the more strain (or strain is MORE and MORE with each unit of added stress). So not a straight line ... curved more. NOT proportional.


What is elasticity:

Elasticity can be resiliant or damped. Explain each and give examples:

The ability of a material to return to its original shape (length/height) after being deformed.

If elasticity is QUICK- it is resilient. Ex: rubber band, billiard ball, and LIGAMENT

If elasticity is SLOW – it is a damped response. Ex: articular cartilage, IV discs, silly putty


With regards to elasticity, what is:

- Creep:
- Elastic deformation:
- Plastic Deformation: (the good and bad)
- Proportional Limit:
- Ultimate strength:
- Rupture Point:

(more below ... scroll)

What is difference between creep and plastic deformation?

The goal of stretching is to accomplish what?

What is the difference between Ultimate Strength and Rupture Point?

- Creep: ability of a material to undergo slow progressive deformation from continuous pressure/load/stretch

- Elastic Deformation: This type of deformation is reversible. Once the forces are no longer applied, the object returns to its original shape (resilient or damped).

- Plastic Deformation: This is elasticity or creep applied, but goes past and creates permanent deformation. Is not reversible. It is when creep becomes permanent and will not recover once stress is released. Good when you stretch muscles, bad when you have a metal stretch too much.

- Proportional Limit: Highest stress at which stress is directly proportional to strain. It is the highest stress at which the curve in a stress-strain diagram is a straight line. Proportional limit is equal to elastic limit for many metals. The point on the load / deformation curve where a materials elongation in shape changes from linear to non-linear ("Hookean limit" and becomes non-hookean).

- Ultimate strength: the max amount of tension or stress a material can take

- Rupture Point: Elongation continues until material breaks

Difference: creep changes objects form a little, then it will return to normal. But plastic deformation changes it permanently.


Ultimate strength is the max it can take. In hookian behavior, it is the same as the rupture point, but non-hookian behavior, there is still intactedness after the ultimate strength point where it becomes even more weak (downward slope) before rupture point/breaking.


With our tendons and ligaments, explain loading and unloading behavior. And when does this process of loading and unloading alter?

So explain what happens with a ligament sprain?

We rarely load our ligaments / tendons to the point of rupture. So they load and unload all the time.

If you stretch (sprain) a ligament, then the loading up line was normal, but it ruptured, and the unloading line moves cause it is now stretched.


Stress (σ) is the amount of __________
Strain (ε) is the amount of ____________

Graphically, if level of strain is off or different (non-hookian) than when it started, what happened?

As a PT, you might stretch a muscle / ligament a bit and if the next day the patient is ok, then do it again. But if they come in the next day and are in more pain, you overdid it and need to tone down resistance/stretching.


Muscle or tendon or tissue thus got elongated or over-stretched (sprained).




(hint: YEILD to a metal object striking you)

Stress at which a predetermined amount of plastic deformation occurs before injury/deformation.

Yield means something has yielded to your intervention.

If we agree if 2% (or 102% of original
Length, it is the agreed
Upon max elongation past normal,
Then if we go past it (point D on
Graph). Anything past that point
Is stretching.


What has a greater yield strength ... metal or biological tissues?

What % can metal vs. tissue be stretched?

Obviously biological tissues.

Planes are made of metal, which can elongate or stretch 2% (or 102%) of its capacity. Past that though it breaks. Biological tissues can stretch much much more.


What is Elasticity

What is Viscocity:

What is Viscoelasticity

So, rate of _______ impacts rate of _________

With silly putty, the faster you _____ it, the more or faster it will ________

T or F: With bone, the faster you load it, the less stiff it will be?

Elasticity: Elasticity is the tendency of solid materials to return to their original shape after forces are applied on them. When the forces are removed, the object will return to its initial shape and size if the material is elastic.

Viscocity: Viscosity is a measure of a fluid’s resistance to flow. A fluid with large viscosity resists motion.

Viscoelasticity: Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. The faster the load, the more viscous it becomes.

Silly putty. How much it will deform is dependent upon how much stress is put on it. The more/harder/faster you push, the more / quicker it deforms.

Rate of LOADING impacts rate of DEFORMATION

Load / push - deform.

False: with bone, the quicker you load it, the more stiff it will be (think of a karate chopper ... quicker is better and won't break your bone).


Hysteresis =

How to remember:

Usually it is displayed or changed how?

What is hysteresis of these materials:

- Bone
- Glass
- Metal

Deformation. It is a lag or delay in the response to a change in force.

Remember: History has a lag in when it is written, and things are lost (heat).

Energy is lost in the form of heat

Bone doesn’t really deform much.
Glass will and then fail
Metal can change a lot when a lot of force or heat is applied.


Is bone better at absorbing compressive forces or shearing stress? In other words, can a bone handle a load in a compressive vs shear way (or longitudinal vs transverse load)?

What is straw analogy related to this?

Compressive (or longitudinal).

You can't really press a straw down from top and deform it, but you can easily hit it from the side and it will bend immediately.


What can cause a compressive force in a bone (give example with tibia/femur)?

What can cause a tension stress in a bone (tibia/femur)?

What can cause a shearing stress in a bone?

Compression: larger weight bearing down with femur on top of tibia.

Tension: Limb hanging holding more weight, or muscle or tendon attachment points on the bone.

Shear: Some rotational movement, or tibia sliding across femoral condyles.


With regards to biological tissues, what is:

- Resilience:
- Damping:
- Toughness:

Is silly putty resilient or damped in returning to it's original shape?

Resilience: Ability for it to return back to normal shape, length, position QUICKLY

Damping: Slow rate of a material to to return to its original shape ... or loading SLOWLY

Toughness: Ability to withstand impact or absorbing high levels of energy before fracturing (drop a steel ball or glass ball onto the floor)



What is friction:

3 factors of friction (and examples):

How to remember the 3 factors?

A force between two bodies which oppose the motion ... OR ... resistance of object to being moved on other objects.

1) How tightly two objects are compressed together (weight of load bearing down)
2) Type of materials compressed together
3) Velocity of object moving on surface taking place

Examples: a heavier box creates more friction than lighter box. A more lubricated surface helps decrease friction. A faster push of the box helps overcome friction easier.


What is the NORMAL force

It's Newton's 3rd Law. Normal force is equal and opposite to the weight force.
(you stomp on ground, and it stomps back)

And it is perpendicular to the surface. So if surface gets tilted, the weight still goes to center of earth, but normal force is perpendicular to surface (and it is a little less since you lose some of the vertical vector force).


What is Amonton's law of friction


Friction depends on or is proportional to the LOAD of the object (not necessarily the surface area). The heavier the object/load, the more friction occurs.

Example: eraser vs. a book, or heavy vs. light box


Difference between static and kinetic friction:

Which one keeps an object at rest? And if static friction is overcome, you get ____________.

Static: Non-moving friction between objects
Kinetic: Sliding friction of moving objects.

The Force of Static Friction keeps a stationary object at rest! Once the Force of Static Friction is overcome, the Force of Kinetic Friction is what slows down a moving object!


Fsmax = μs N

Maximal friction occurs right before _______ occurs

T or F: Ff = Fs (if "f represent friction and "s" represent slide or push)

T or F: Ff = Fmax

Ff = Fs until what?

T or F: If you increase the pulling or pushing force, or the weight of the object, the friction increases?

Force = normal force times whatever coefficient is of static friction (which is dependent upon the object/surface).

Slipping (movement) ... kinetic

TRUE. Ff = friction, and Fs = sliding force in opp. direction. They always equal each other.

FALSE: Ff is equal (but opposite direction) of the push force (Fs). It is only = Fmax when max amount is reached.

Ff = Fs until you reach/overcome Fmax ... then you get kinetic friction.



f = μk N

Force = normal force times coefficient of kinetic friction


Is normal force (N) parallel or perpendicular to the surface?

Is it in same direction or opposite gravity/weight?

Is the Normal force basically the Ground Reaction Force (GRF)?

If an object is now tilted on a ramp, will the amount of the normal force be more, the same, or less? Why?

Does weight or gravity ever change directions?

N is perpendicular to the surfaces

Opposite. It opposes gravity. Book pushes down on table, N force pushes up.


It would be less. Because now you have 2 vectors, and part of the same amount of force is distributed to the other vector.

No, it always points to the center of the earth.


T or F: If you pull a heavy box and it doesn't move, the more you pull, the more the static friction increases?

T or F: Then if static friction is overcome, kinetic friction occurs?




μ =

If you had a rubber crutch on tile and it's μ is 0.30-0.40, would that coefficient number go up or down if you put the crutch on a wet surface?

T or F: Articular cartilage is much much much more slippery than our best orthopedic replacement.

T or F: the higher the friction coefficient, the more slippage will occur, or the quicker kinetic friction will occur.

How does friction (and wetness vs. dryness) relate to joints in our bodies?

FRICTION coefficient

Way down.


False. A friction coefficient of 0.03 is metal on ice. A friction coefficient of 0.7 is rubber on cement.

Most joints are synovial, which have synovial fluid. One purpose of synovial fluid is to reduce friction between bones and tendons.


FLUID viscocity =

Example of a large viscous fluid, and a low viscous fluid

Do high viscous fluids flow faster or slower than low viscous fluids?

Fluid friction (or resistance to flow, or fluid shearing stress)

Large: honey
Low: water



Difference between laminar flow vs. turbulent flow of fluid friction

Does fluid flow better/quicker in Laminar or turbulent?

Imagine a cross section of a hose or vessel, will flow be quicker centrally or along walls?

What is Newtonian fluid? Example

Laminar Flow: the flow of a fluid when each particle of the fluid follows a smooth path, paths which never interfere with one another. One result of laminar flow is that the velocity of the fluid is constant at any point in the fluid.

Turbulent Flow: irregular flow that is characterized by tiny whirlpool regions.


Centrally because there is less friction. There is more friction along vessel / tube wall (and each layer gets less and less fast closer you get to wall)

Remember Newton's 1st law -- an object will stay in motion unless a force acts on it (or stay at rest). So water will keep flowing unless friction, force, plug, heat stops it. Example - in a pool if you move arms slowly, you get a bit of resistance, but the faster you move your arms, the more resistance you get.


T or F: the faster a fluid flows, the more resistance it will experience?



What is a Thixotropic Fluid

Examples of Thixotropic fluid

The fluid thickens with slower shear (flow) rates and thins with faster shear rates = shear thinning.

Synovial fluid (fluid thickens with slower flow rates). Or backing liquids that get thinner if mixed.


What is Dilatan fluid


Slower it flows, the thinner it gets.
The faster it flows, the thicker it gets.

Blood, or some cooking



- Need calculator
- 55-65 questions (one point each)
- Interpretation of diagrams
- Short answer and problem questions (6-10 questions for 30 points) ... use paper and pencil
- He'll provide diagram
- ROUND TO 2 decimal places
- NEED to know equation for torque, friction, etc.
- There will be a problem on these equations: COM, Torque, Friction calculation
- It is timed, so don't waste 15 mins on one problem



Muscles do have origins and insertions, that is true. But think of them more as ATTACHMENTS proximally and distally. Usually the proximal stays in place and the distal moves (but not always). But, also remember that the FIXED end will not move, and the free end WILL move.

Give examples of this by describing how this works with:
- Hip abductors
- Iiliopsoas muscles
- Quads (when tibia is fixed)
- Quadratus lumborum

HIP ABDUCTORS: Normally the gluteus hip abductors pull the thigh OUT and abduct it from the hip. BUT, usually the thigh (leg) is fixed on the ground and won't move. So instead, it pulls the pelvis (and thus trunk) laterally.

ILIOPSOAS: Also with iliopsoas ... normally it flexes the thigh. But if thigh / leg is fixed, it will bend and flex the trunk forward.

QUADS: If tibia is fixed and won't move, and you are bending down, if you flex your quads, they will contract and pull your femur (and thus your trunk) forward.

QUADRATUS LUMBORUM: Can either flex trunk forward, or extend back (or hike up hips)


Remember the homework assignment problem of the weak hip abductor with the cane.

What side would you use a cane if you had weak left sided hip abductors ... and why

You would put the cane OPPOSITE the effected / involved / BAD leg. So on the RIGHT side.

Because if left hip abductor is weak, you will naturally lean over your right leg (causing a torque to the right). If you put cane in left hand and push up, that causes another torque to the right and that would put you off balance. You need to put it in the RIGHT hand by the good leg to COUNTER the torque to put you more at equilibrium, and widen base of support for the bad (LEFT) leg.


What does static equilibrium mean?

Formula for SE?

What is Dynamic equilibrium?

Means an object is not moving (up, down, left, right, or rotation). ALL the forces and torques equal each other, so net forces equal 0 and so no movement.

Sum of Torques (T) = 0

When an object is moving and torques on each end are equal (like steering wheel).


Can an object be in movement/motion if the net forces are 0?

This is the difference between STATIC EQUILIBRIUM and DYNAMIC EQUILIBRIUM.

So, if torque amount is equal to each other on both side, if their direction opposes each other, then NO movement because it is static equilibrium.

BUT, if torques are equal and directions are same motion, you get movement = dynamic equilibrium. Think about a steering wheel. If force on one end is applied in opposite direction as the same magnitude of force as the other end, the forces equal each other, but it causes rotation of the bar.

A stationary object remains stationary (static equilibrium) if the sum of the forces acting upon it - resultant force - is zero. ... If the resultant force acting on an object is not zero, a stationary object begins to accelerate in the same direction as the force.


So, for real static equalibrium, what must happen:

Forces must equal 0

Rotation (Torque) must equal 0 (rotational movements opposite each other)


T or F: Torque can be thought of as a ROTATIONAL force?



What is the lever arm (r)?

Another name for lever arm?

It is the distance from the AOR to the force (or perpendicular distance from AOR to force)

Moment arm


Will a large or small lever arm (r) create more torque or rotation? Why?


T = F x perpendicular distance. Lever arm is the perpendicular distance, so the larger it is, the more torque you get.


Fixed Pulleys ___________

Moveable Pulleys ___________

CHANGE DIRECTION (pulley is fixed and doesn't move, just rotates to change direction of force).

SHARE the LOAD (pulley moves)


What is a machine?

Why do we use them?

Something that multiplies or changes directions of a force.

So you can do more with less - get more work done.


What is the law of conservation of energy?

Can energy be created or destroyed?

Total Amount of energy never changes / dissipates / destroyed. But it can transform from one form of energy to another, or from one object to another.

Energy can NOT be created or destroyed.


Formula for work:

How does this relate to pulleys?

W = force x distance

If you increase the force, you increase the work.
If you increase the distance, you increase the work.


What takes more effort - lifting 100lbs with one fixed pulley, or lifting 100lbs with several pulleys?

The more pulleys you have, the less work you have to do.


Which kind of pulley just changes the direction of the pull, but not the magnitude or amount of force needed?

What kind of pulley will 1/2 the amount of force needed to lift object (or share the load)?

So if I reduce the amount of force needed by 1/2, what happens to the distance needed to lift object? Why?

So, more rope =

Fixed pulley

Moveable pulley (single) ... if you had 2 moveable pulleys, it would require 1/4 the effort on your part.

It doubles. W = F X D

More work, or Less force to do same amount of work


In a single fixed pulley system, how much force must be applied to move a 5kg weighted object?

With 8 different fixed pulleys, how much force must be applied to move a 5kg weighted object?

If I had one moveable pulley, how much force must be applied to move a 5kg weighted object?

3 ropes are attached to a moveable pulley, with 5kg weighted on it. How much force to lift it?

5 kg


2.5kg (because the moveable pulley shares the load)

1.67kg (5/3 = 1.67)


If a rope comes off (vertical) a moveable pulley and then to a fixed pulley, do you count/add the force from the fixed pulley?

NO. Fixed pulleys just change direction of the force, not magnitude.


T or F: with calculations dealing with MOVEABLE pulleys, you only deal with the vertical component of the force? In other words, the VERTICAL component of a moveable pulley does the lifting/holding?


Use trig (soh cah toa) to figure out what the vertical component measure is.


A 10kg force pulled through a fixed pulley can lift how much weight?

If I pull with 5kg of force through a fixed pulley that runs to a moveable pulley, how much weight would the moveable pulley lift?




Review the PULLEY problem set questions



Normal force is always _________ to the surface of an object.



Fsf =
Fsmax =

Is Fsf = Fsmax?

So an object remains at rest so long as Fsf is greater/less than Fsmax?

An object slips when Fsf is greater/less than/equal to Fsmax

Is it possible to have Fsf > Fsmax?

Static friction
Maximum force of static friction

No. You can have static friction (book stuck not sliding down a slope) up till the point it reaches maximum static friction. Once max is reached it is equal until Fsf goes just above and then book moves and kinetic friction takes over.


Just barely more

NO ... this is when kinetic friction happens.


Explain difference between static friction and kinetic friction

Static friction is the friction that exists between a stationary object and the surface on which it's resting. A frictional force occurs when you try to push an object alongside a surface (but still doesn't move).

Once the objects start moving, kinetic friction takes over.


Remember that tough pulley problem where you didn't understand why the one rope coming in at an angle to a moveable pulley was the same magnitude (amount/force) as the straight up and down rope on the other side of the moveable pulley.

Here is why:

REMEMBER: The magnitude of the two vectors associated with the moveable pulley are equal REGARDLESS of the angles at which they are oriented. BUT, the vertical traction force is created by the vertical components of these vectors only.


T or F: Friction force always acts in the opposite direction to movement / force / tension?

T or F: The force of the movement is equal to the friction force (until it overcomes the max frictional force)




After completing a practice problem, if you get a negative force, what does that mean?

So if you get a negative force, that doesn't mean negative magnitude (or a negative force), it is just the DIRECTION of the force (positive or negative direction).


What is a vector?

What is a force?

What is a torque?

Vector: A quantity with both a magnitude and direction

Force: a magnitude in a direction (F=ma)

Torque: is a force acting about an axis of rotation from a perpendicular distance that causes rotational movement.


Remember the problem with Lance squating in equilibrium ... how did the right hand rule work?

If you take out all other torques/forces, isolate the one and how will it move about the axis (if acting alone regardless of other torques/forces)? If clockwise it is negative, if counterclockwise it is positive.


"Cervical Traction" would mean what?

A pulling force to relieve compression across a joint (in this case, the cervical area).


And remember to draw a curved arrow any time you are doing a TORQUE problem, and positive/negative arrow for force problems.

And draw the x,y,z diagram to tell what directions of forces are what.



For the 3 lever systems, do they have a good mechanical advantage or not? (Remember what mechanical advantage is):

Mechanical Advantage is ration of ┴df / ┴dr ... or distance of force / distance of resistance. If distance of force is MORE than distance of resistance, you will have greater mechanical advantage

1st Lever: Poor
2nd Lever: VERY GOOD
3rd Lever: Bad (tendon is close to AOR)


Below are flashcards on power point 3A on connective tissue



What is the purpose of connective tissue?

To connect things together :)

Connect cells to cells, bones to bones, ligaments to bones, muscle compartments (fascia), etc.

And give support.


The components of Connective tissue are (and their function):

- Cells (life/tissue/divide)
- Fibers (give tensile strength)
- Ground substance (gel that binds it all together)


The behavior of a material (connective tissue) under a load is determined by:

1) Properties of its components
2) Amounts of its components
3) Orientation of its components
4) Stress of load


What is the hardest or toughest connective tissue?



There are 3 arrangements of bone. What are they and explain each?

1) Woven: Immature or disorganized bone (in fetus or after a fracture)

2) Cortical: Mature bone and highly organized with lots of osteons / haversian systems.

3) Cancellous: Spongy bone (epiphysis areas)


Are an osteon and haversian system synonymous?

Which type of bone is near a joint?

Which type of bone is most mature?

Which bone has osteons?

Which bone would you find in a fetus or after a break?

Where along the bone would you find the cancellous and the cortical part of the bone?






Cancellous is up near joint in epiphysis area. Cortical is hard mature part along diaphysis/shaft.


T or F: Bone is always changing, is dynamic, and remodeling?

T or F: Bone will fracture more easily longitudinally than transversely / laterally?

Bone is innervated?

Bone is vascularized?

Bone is a calcium reserve for the body?



Well ... periosteum is innervated, not bone, but periosteum covers the bone

Yes, highly vascularized

Yes, calcium reserve


What is Wollf's law regarding bone:

(How can you remember this?)


Wolff's Law states that bone grows and remodels in response to the forces that are placed upon it. After injury to bone, placing specific stress in specific directions to the bone can help it remodel and become normal healthy bone again.

People don't like PT's because they inflict pain. Wolves inflict pain, so people don't like them. But the PT's pain they inflict (tension, compression, shear, stress) is GOOD pain.


Functions of bones are:

- Produce RBC's in bone marrow
- Provide calcium / calcium reserve for metabolism and muscle contraction
- Structure
- Protection
- Movement
- Distribute forces
- Lever system for body


Osteoclasts ________ bone to so more/new _________ can be laid down

Break down



3 types of cartilage:

- About
- Function
- Examples
- About
- Function
- Examples
- About
- Function
- Examples

1) Fibrocartilage:
- About: Lots of fibers and some ground substance (gel), damped resistance, creep
- Function: withstand compression, handle stress
- Examples: IV disc, pubic symphysis, meniscus

2) Hyaline cartilage
- About: less fibers, more ground substance
- Function: Flexible junction, resists deformation (good compressive strength)
- Examples: Costochondral junction, skeleton of baby

3) Articular cartilage
- About: Very hydrated (lubrication) cause it's mainly water, thin, avascular and aneural, nourished by synovial fluid, can't repair well at all, at ends of most long bones
- Function: Lubrication, reduce friction, reduces shear stress
- Examples: all joints


Is articular cartilage elastic? Why or why not?

If you stand for a while your articular cartilage gets a little stiff. What do you do?

Would articular cartilage have a high or low coefficient of friction? Why?

T or F: as the water content in AC increases, the cartilage becomes more stiff and less permeable?

AC is typically damaged from compression, tension, or shear stress?

Yes, it has a lot of water in it and around it.

MOVE. That gets joint capsule to release synovial fluid to lubricate and nourish articular cartilage.

LOW since it is lubricated, and more lubrication equates to lower coefficient of friction.

False. More water = less stiff and more permeable.



What is osteoarthritis

Can AC repair itself and heal?

When AC at ends of bones starts to wear down. AC wears down and bone rubs against bone ... very painful.

Typically NO because it has no vascular supply to regenerate. That is why people eventually get a THA or TKA because osteoarthritis gets so bad.


Dense irregular vs. dense regular connective tissue is pretty similar. But what are the main things that differentiate them?

Would a tendon and ligament be examples of irregular or regular dense connective tissue?

- How tightly fibers are packed (dense reg. is more)
- Orientation of fibers (dense reg. is more organized)
- How well they resist forces (dense reg is better/stronger)

REGULAR (tendon even more parallel)


What is the most abundant cell in connective tissue?

What is the ECM and what is in it?


Extra cellular matrix ... outside the cells where you get the meshwork of fibers in the ground substance.



- Do they push or pull?

- Are fibers oriented longitudinally to the force of pull or transversely?

- Do tendons have a lot or little ground substance?

- Do tendons have a lot or little slack?

- Are tendons or ligaments more viscoelastic?








- Main function of ligaments:

- Are ligaments or tendons better shock absorbers? Why

- Are fibers more parallel in tendons or ligaments?

- Resist joint movement and connect bones (structure and support between joints)

- Ligaments are better. They have more ground substance and elastin, so can take more shock

- Tendons


Imagine a stress/strain curve plotted for a tendon or a ligament being stretched to the point of sprain. What are the 6 major points along the curve / plot?

Does complete failure happen at the tip (very highest point) of the stress / strain curve?

The Yield point indicates what?

- Toe (slack)
- Hookian region (each unit of stress adds a unit of strain)
- Proportional limit (point where stress/strain stops being linear or hookian)
- Plastic deformation (past point of elasticity - microfracture)
- Ultimate strength / Yield Point / Major failure
- Complete failure (rupture)

It happens after in non-hookian material, and at the tip / ultimate strength / rupture point with hookian material.

Yield point is end of elastic region and start of plastic region


A ligament is viscoelastic, so what does that mean it does?

T or F: failure (injury / sprain) of a ligament or tendon is more likely to happen in the middle (belly) than at the end or attachment point?

It gets stiffer the quicker it gets loaded. If rate of load is high, then stiffness is quick.

False. Failure (injury / sprain) or rupture happens more at the attachment point of the bone, because that is where it is weakest.


What is an avulsion fracture?

Not a fracture of the bone, it is an injury to the bone as a result of the tendon / ligament fracturing or tearing off a piece of the bone at the attachment site on the bone.


What factors contribute to how a ligament / tendon might rupture / avulsion fracture / sprain?

- Age of person
- Strength of ligaments / tendons
- Speed of applied force


As PT's we will put loads on ligaments and tendons to strengthen them. There are 2 approaches to how you can do this, and why. Explain:

- Don't put extra load on a muscle/tendon/ligament, but stretch it and let it stretch. This will increase the length without adding load.

- Apply more and more load to add strength and stretch to a muscle / lig / tendon.


What causes a tendon or ligament to become weak?

- Are your tendons/ligaments more elastic in your youth or older age?

- Does temperature effect ligaments/tendons elasticity?

- Prime age of elasticity, and when does it start to go downhill?

- Age
- Load (compression)
- Stress/strain/tension
- Shear
- Severity of injury


- Yes, the hotter it is, the more elastic they are.

- Prime age is 20 or so, and goes down hill around 35.


Explain what cortisone is, why it would be used, effects, etc.

Cortisone is basically a steroid. When you have a muscle / tendon / bursa / ligament pain (strain, sprain, tear), it causes inflammation. A cortisone shot will reduce the inflammation and reduce the pain and friction, but won't solve or heal anything.


T or F: The higher the temperature, the less stiff your connective tissues are?

Can you relax more and stretch farther in a snow bank or a hot tub?

Would injury be more prevalent or less prevalent in hotter weather?


Hot tub

Well ... because you have more elasticity in hotter weather, it has more stretch so won't tear as quick. But, because of this, you can then overdue it and push to hard, and lead to injury.


T or F: Bouncing during a stretch is better than holding a stretch? Explain

T or F: Exercise will always help counter-act the natural forces associated with aging? Explain

NO. Bouncing leads to a tear, but holding helps create plastic / elastic deformation and permanent elongation.

True. Exercise helps keep muscles stretched, joints lubricated and nourished, ligaments strong, etc.


Do PT's apply loads and stress on tissues (bones, muscles, tendons, ligaments)? Why? This is called ________


If PT's do it too much though, it could lead to _________

YES. Increased load and stress strengthens it. It is called REHAB.



What is Rheumatoid Arthritis

What does it lead to?

Rheumatoid arthritis (RA) is an autoimmune disease in which the body’s immune system – which normally protects its health by attacking foreign substances like bacteria and viruses – mistakenly attacks the joints. This creates inflammation that causes the tissue that lines the inside of joints (the synovium) to thicken, resulting in swelling and pain in and around the joints. The synovium makes a fluid that lubricates joints and helps them move smoothly.

If inflammation goes unchecked, it can damage articular cartilage as well as the bones themselves. Over time, there is loss of cartilage, and the joint spacing between bones can become smaller. Joints can become loose, unstable, painful and lose their mobility. Joint deformity also can occur.

Leads to:
- Aches and pain through joints
- Swelling in and around joints
- AC gets eaten up
- Bones get weak and painful
- Joints become lax or disjointed / deformed
- Lose strength in joints


How might you stop Rheumatoid Arthritis

Steroid injection to stop the inflammation / block inflammatory process so bones and AC don't get broken down. But stopping inflammation process also stops the healing of tissue process too.


Below are flashcards on Power Point 3 B - Biomechanics of Bone



Nutrients to bones are distributed through what?



Will a broken bone bleed?

Yes of course, bones are highly vascularized


What tears down old osteons?



Once osteoclasts tear down old osteons, new cells form new osteons. What are those new cells?



T or F: Bone is viscoelastic?

True. It has viscocity and elasticity, and the faster you load it, the stiffer it will be.


Bone is an anisotropic material. What does that mean?

What was the example of this Dr. T gave in class?

(How to remember)

Isotropic means the material and properties of that material are the same throughout entire object, and same orientation.

Anisotropic is opposite where material and properties (and orientation) are not the same throughout

So think of how there is a cortical and cancellous part of bone.

Remember a bone has parts (longitudinally, 30 degrees, 60 degrees, and transversely) where it has different strengths or abilities to withstand forces).

(How to remember: ani is so DIFFERENT in the tropics)


Because bone is viscoelastic and anisotropic, what does that mean?

Bone’s mechanical properties vary with the direction of loading

Bone’s mechanical properties vary with the speed of loading (bone is viscoelastic)


Generally, will a bone break by simply compression alone, tension alone, or shear alone?

T or F: Most loading incorporates elements of compression, tension and shear

So imagine those tall boxes with little diagram boxes in it.
If a bone gets pulled / tension force, what forces happen?

If a bone gets compressed, what forces happen?

If a bone experiences shear, what forces happen?

No, not usually. It is very uncommon to see a break of just compression, tension, or shear of a bone.


Pulled: tension and shear
Compressed: compression and shear
Shear: tension, compression, shear


So explain BENDING with a bone break.


When a bone bends, one side experiences compression, the other side experiences tension.

If you get hit from the side, that side will bend in and experience compression, while the opposite side bends also by experiences tension. Or a skiier falls forward, the front of tibia will experience compression and back of tibia will experience tension.


So explain TORSION with a bone break.


Where one end of bone is fixed, and the other end of bone twists / rotates.

If tibia is planted on ground and you twist your hip, it will twist at knee and cause torsion.


So explain COMBINED with a bone break.

When you stomp on the ground (compression) and then twist (torsion).


Imagine the tibia or femur, does the epiphysis or diaphysis have larger cross sectional areas (CSA's)?

Will a larger CSA have greater / weaker strength against torsion?

Will a smaller CSA have greater / weaker strength against torsion?

So would the epiphysis or diaphysis be more susceptible to a break / fracture? Why?

Epiphysis (ends)


Weaker (increased risk of fracture)

Diaphysis, smaller CSA


Would bone be stronger resisting compression forces or shear?

So since bones experience compression, tension, and shear forces at once, if a fracture happened, what force would it tear from? In other words, if you are skiing and fall, the front of your tibia experiences compression as you fall, and the back of the tibia experiences tension. If you twist slightly, you experience shear. Where would the break happen first?

Compression for sure

Tension or shear


How do muscles work or compensate when bones experience these forces?

*** The WHOLE PURPOSE of muscles contraction during a possible break scenario in a bone is what:

Muscle contract to counter-act the force and help compensate to create compression (stronger) on both sides of the bone.

*** Muscle-bone interaction reduces TENSION loading forces to increase compressive loading forces since bone can handle compression much much better.

Usually fracture is a tension fracture. Muscles add opposite or compressive force on the tension side, so fracture goes from tension to compression. To fall and
get a compressive fracture is much harder to do. Muscles try and counter out tension force by adding to or forcing a compressive force.


T or F: usually if you break a bone, it is a compression fracture? Why or Why not?

NO. Usually it is a tension (or shear) fracture. Because bones can handle compression forces much better than tension / shear forces.


With regards to your hip:

- If you step down and put weight on leg, what happens to the femoral head/neck? Which directions does it rotate?

- So where is compression, and where is tension during act of putting weight on leg?

- Where would a break more likely happen with regards to femoral head/neck?

- How is this counter-acted so a break doesn't occur?

- Down and medially

- Compression is down / medially, tension is up / laterally

- Lateral neck of femur where there is tension (up/lateral)

- Your hip abductor muscles pull the femur up to release tension and help force more compression on lateral and medial side, so you limit the amount of fractures.


T or F: Muscle contraction forces can exceed the compressive strength of bone and cause compression bone fractures. Why or why not?


If you have too large of a contraction of the muscle, or a weak bone - you can get a compressive fracture.


Bone is viscoelastic. What does that mean?

So should a boxer or karate chopper hit harder or softer to avoid injury?

Would a skiier get an injury early on or later on in the day? Why?

Would you more easily/quickly break your bone when you are older or younger?

Means the more / quick the load, the faster it responds and becomes stiff. And opposite - the slower you load, the more easily it could break. Bone’s modulus of elasticity and its strength increase with increasing loading rate


Later on in the day. After a while, muscles become weak, you go slower, and so loading of bone is slower, with weak muscle to counter-act forces, so breaks happen easier.

The older you get, the weaker your bones become, and the weaker your muscles become, and the weaker your effort / force during activities, and reflexes. Injuries happen much more with older patients.


Osteoporosis =

Weakened bone over time. Bones get old, people don't exercise and strengthen them (put pressure and resistance on them), etc. So bone becomes weak and wears down over time.


Bones calcify and remodel. What does that mean?

After a break, cells flood the area to calcify (called a callus) and heal it. Then over time they remodel (or reshape) into their proper anatomical shape.


Remember all those curved graphs.

- If it is straight up and back down, it is:
- If it is straight up and then slightly off (to the right), it is:
- If it is straight up and then way to the right:

- Perfectly resilient
- Resilient (but slightly damped)
- Damped


*** Remember to go to green binder and review all the formula's and principles of Physics, as well as the graphs (behind problem sets answers).



Redo and practice ALL the physics problem sets, but especially the 1st Friction problem and the last Friction problem.



Below are the flashcards on the JOINTs power point 4A



What is a joint?

Another name for a joint:

Union of 2 or more bones.



What are the 2 main functions of joints:



Name some examples of joints that provides stability

Name some examples of joints that provides mobility

Suture, teeth, interosseous membrane

Knee, elbow, shoulder, ankle, etc.


What is the difference between an anatomical joint and a physiological joint:

Anatomical: Two (or more bones) and the tissues that directly connect those bones (ex: ligaments, capsule)

Physiological: The anatomical part (described above), plus the other surrounding tissues (ex: tendons of muscles ... probably fat and vessels and skin surrounding joint).


What are the 3 classifications of joints:
- Name
- Description
- Purpose/Function
- Examples

(How to remember)

- 2 or more bones connected with NO joint cavity
- Little movement, disperse forces
- Sutures of skull, teeth, interosseous membranes

- Bones connected by hyaline or fibrocartilage. Very little movement, and no joint cavity
- Hyaline Cartilage (Synchondrosis) = costochondral and manubrio sternal joint
- Fibrocartilage (Symphysis) = pubic symphysis, intervertebral (IV) disc

Diarthrosis (SYNOVIAL):
- Has a joint capsule, lots of movement, most joints in body
- Knee, ankle, hip, shoulder, elbow, etc.

(remember: SAD ... Sin so I can't move; Amphibians have cartilage; I'd die without synovial joints)


What are the components of a diarthrosis (synovial) joint:

- External lig's
- Fibrous Joint capsule
- Joint cavity
- Synovial Membrane
- Synovial Fluid
- Articular cartilage
- Vessels and nerves
- Sometimes: a labrum, fat pad, inter-articular lig's, bursa


Explain difference between uniaxial, biaxial, and multiaxial joints ... give examples:

3 axis' / planes of motion (sagittal, frontal, transverse)

Uniaxial Synovial Joint: Occurring around one axis, movement only in one plane. Examples: pivot and hinge joints. Knee, elbow.

Biaxial Synovial Joint: Occurring around 2 axes at right angles to each other; Examples: saddle and condyloid joints. Thumb, ankle.

Multiaxial Synovial Joint: Occurring around several axes; Examples: plane ball and socket joints. Shoulder and hip.


What does "degrees of freedom" mean

How many degrees of freedom does a biaxial joint allow?

The number of axis' or planes a joint can move ... so uniaxial, biaxial, triaxial/multiaxial.



Do all synovial joints have 6 degrees of freedom?

Technically yes, but may have very very limited (restricted) movement and ROM in 2 of those planes. I can take my ulnohumeral joint (which traditionally is a uniaxial joint or 1 degree of freedom) and I can get a little movement in every other of the 6 degrees. The more I have movement in those other 5, the more pathology I have. Means a ligament or tendon is torn which gives me more ROM / degrees of freedom in a plane not normally moveable.

Also the plane joints of the carpal bones have multiaxial movement, but very very limited in most planes.


T or F: A joint can move in a translational way, a rotational way, or both?



Is the axis of rotation or joint axis the actual anatomic axis? Explain

Well, not really. The exact anatomic axis actually changes as you go through a full ROM. We as PT's will use goniometer and need to all be consistent as PTs, so we use as close to joint axis as we can, but understand the actual anatomic axis or joint center will move as the joint goes through full ROM.



It is the AVERAGE "joint axis" as the joint moves through ROM.

So remember example of tibia moving with respect to femur. The exact center or axis of motion changes throughout the ROM. We need to estimate the average - this is the instantaneous axis of rotation or Instant Center.


Even though we use the Instant Center, the reality is that the Axis of rotation moves (like in example from last slide). This changing axis of rotation is called =



So what is the Evolute:

The path or arc of all the different locations of the instantaneous AOR as a joint goes through ROM.


What are the sub-classifications of Diarthrosis Joints, and give examples:

(Go from least mobile to most mobile)

Numonic to remember:

Hinge joint: Elbow, PIP, DIP, Knee, Ankle (uniaxial)

Pivot joint: C1 and C2, radio-ulnar jt (uniaxial)

Condyloid joint: Radio-carpal, Metacarpal phalangeal (biaxial)

Saddle joint: Thumb (biaxial)

Ellipsoid joint:

Plane joint: Carpal bones (multiaxial)

Ball and Socket joint: Hip, Shoulder (multiaxial)

Harry (u)
Potter (u)
Can (b)
See (b)
Every (b)
Person (m)
Beautifully (m)


Explain difference between Ovoid and Sellar joints:

Examples of Ovoid joints:

Examples of Sellar joints:

Ovoid: where one end is convex, and one is concave. Like a computer mouse.

Sellar: Each partner/end has a concave and convex part. SELLAR is like a SADDLE.

Examples of Ovoid jts: hip, knee, digital joints

Examples of Sellar jts: subtalar, carpo-metacarpal joint (thumb/saddle)


What is Osteokinematics:

What is Arthrokinematics:

Give example of both:

Osteokinematics: is what you see with your eye of the bone movement. Movement of one bone with respect to another bone. Doesn’t consider the joint, just care and look at motions of the bones. It is what we look at and see with our eyes.

Arthrokinematics: is what is happening in joint (you usually don’t see). Movement of the joint within, not considering the bones moving distally.

If I abduct my arm up, the humerus moving with respect to the scapula is osteokinematics. But if I can get down and see inside the joint, the movement there is arthrokinematics, and it in fact is different movement because the humerus moves UP with osteokinematics, but that same movement makes humerus go DOWN with arthrokinematics.


What is active joint movement vs. Passive joint movement:

Active Joint Movement: actively performed by voluntary muscular contraction

Passive Joint Movement: under voluntary control but is produced by an external force (like the PT)


If femur is fixed and tibia rotates around knee joint, or if tibia is fixed and femur rotates around knee joint, is this the same motion biomechanically?


Whether proximal (femur)
Is stable, or distal (tibia)
Is stable, from a bio-mechanics
Perspective, this is the same
Movement, and quads work
On both, just diff. ends of muscle
Activates and moves.


Explain Joint Play:

Explain Traction:

Joint Play: Pull apart two joint surfaces into least pack play/position. PT’s do it to know if a joint has laxity.
If the joint doesn’t, its a problem. So you need to stretch m’s or lig’s to create elasticity.

Traction: Is a pulling force (by PT), pulling a joint to relieve pressure/compression. Cervical traction as an example.


What are the 3 movements the femur can do on the tibia?

Do they happen separately from each other?

1) If tibia is fixed, and femur rotates, which directions will femur move with respect to tibia?
2) If femur is fixed, and tibia extends out, which directions will tibia move with respect to femur?

Slide / Glide

If I extend my knee, the femur will roll and slide on the tibia. If I twist while doing it, I could get all 3.

1) Femur would roll forward and slide backward on tibia.
2) Tibia will roll forward and slide forward.


Is the AOR always in the convex or concave member (bone)



Explain the Law of the Joint or the Concave-Convex Rule with regards to osteokinematics and arthrokinematics.

Example 1: So if a person can NOT abduct their arm up, which way do you as the PT apply a rehab force?

Example 2: If a person can't extend their knee sitting, which way do you as the PT apply the rehab force?

Convex on Concave: If convex bone is distal or moves with respect to the concave (shoulder), the osteokinematics and arthrokinematics will go in opposite directions.

Concave on Convex: If the concave bone is distal or moves with respect to the convex bone (tibia on femur) then the osteokinematics and arthrokinematic motions are the same direction.

Example 1: DOWN or opposite the movement they can't do (so humerus goes down in glenoid fossa).

Example 2: Push tibia anterior (same direction they can't move). So if extension is weak, extend it for therapeutic purposes to exercise and stretch that tissue to help with rehab/elasticity.

If osteokinematic and arthrokinematic movements are the same (like tibia) you’d apply force same motion as movement. But if they are opposite, apply force opposite their painful movement.

So, someone comes in with injured MCL and they can’t extend, because tibia is same movement for osteo and arthrokinematics, you move tibia in direction (extention) to stretch it. But with shoulder rotator cuff injury. If deltoid
and supraspinatus are injured, so you can’t abduct, you push humerus down for therapy/stretch/elasticity because osteo and arthrokinematic movement is opp (bone goes opp. Joint movement).


Explain difference between least pack position and close pack position, and why you'd use both:

Least: This is when you want the LEAST amount of tension on that joint, so you minimize tension on lig's and tendons, and expand joint capsule as much as you can. Pull the two bones apart and give joint some breathing room. This position gives you the MOST joint play. You'd do this if someone injured a joint. If patient injures a joint, they naturally hold their limb/joint in the least pack position.

Close: This is the locked position. You push articular surfaces together tightly. Tightens the ligaments and capsule, so lots of tension and stability, but any further movement might cause a tear. If I had to self defend myself, I'd put opponent in a joint lock (close pack) position and then go just further and snap something :) Or PT might want to lock one joint in order to mobilize another adjacent joint without help/assistance from that joint.


Is the hip joint more or less congruent than the knee?

Why is the hip more/less congruent than the knee?

What does the knee rely on for congruency?

Hip is way more congruent than the knee.

Head of femur fits perfectly into acetabulum = lots of congruency. But the femur on the tibia is awkward. Femur condyles are rounded, tibial plateau is flat, etc. Knee is more for mobility and not as congruent.

Lots of ligaments.


What is a kinetic chain:

What is a kinematic chain:

How forces distribute through body segments through joints.

How movement (without forces) distributes through body segments linked by joints.


Open vs. closed kinematic chain:

When running, do you use open or closed kinematic chain:

OPEN: A kinematic chain in which the distal segment is not “fixed” or is free to move.
Movement at any one joint in the chain does NOT demand movement at any other joint in the chain. Think of leg dangling of plinth and you raise it up / extend.

CLOSED: A kinematic chain in which segments at both ends of the chain are fixed to a surface.
Movement at any one joint will demand movement of AT LEAST one other joint in the chain. Think of leg pushing a weight machine and knee in the middle of the two closed chain ends produces movement.

If the distal end (tibia) is fixed, and you move proximal end (femur/trunk) around a joint (knee) - that is a CLOSED kinematic chain.

If the distal end (tibia) is free, and you move that distal end around a joint (knee) that is a open kinematic chain.

RUNNING: You use both. If tibia is fixed on the ground, you are in CLOSED. As tibia is free / lose, you are in OPEN.


Below are the flashcards on the MUSCLE power point (4B)



Quick review of muscles ...

1) What are 3 layers around muscles?

2) What creates the movement of a muscle contraction?

3) Of the I, H, and A zones, which ones move

4) Does z line move?

1) Epimysium -surround the whole muscle
Perimysium - surround the muscle fascicles
Endomysium -surround the individual muscle fibers

2) Contraction results from cross-bridges forming between the actin and myosin molecules (power stroke).
Initiated by impulses from the motor neuron

3) I and H move, A does not.

4) Yes, sarcomere walls/ends gets closer to each other during crossbridging


What are some of the architectural arrangements of skeletal muscle (and examples):

- Parrallel (or Fusiform / Strap): Parallel m's are SCM, Sartorius, gracilis .... but fusiform is more of a wider belly like biceps or psoas.
- Spiral (heart, levator scapulae)
- Circular (orbicularis oculi/oris)
- Convergent (pectoralis major, traps)
- Pennate
Unipennate (extensor digitorum longus)
Bipennate (rectus femoris)
Multipennate (deltoid)


T or F: Pennate muscle fibers are longer than parallel muscle fibers?

T or F: With the sartorius muscle, as an example, from proximal to distal end is one long fiber?


False, multiple fibers connect throughout to give it its long length.


If a long parallel muscle had 16 sarcomeres in it, and another muscle had 8 sarcomeres in it, but each sarcomere from both examples retracted to 60% of it's original length, which one would shorten more?

Which one produces a larger or stronger contraction

The one with more sarcomeres

The one with more sarcomeres


Define joint excursion?

Well if I go on an excursion, I go on a trip. So a joint going on an excursion means joint movement?


So would pennate or parallel muscle fibers provide more joint excursion?

Would pennate or parallel muscle fibers provide more force/tension?




T or F: Muscle fibers can shorten approximately 20–30% of their length

Wrong - it is 50-60%


Lets say the biceps attaches in its normal spot of the radial tuberosity, and then it moved the radius at that point 2cm up (ex 1). Now pretend the biceps attachment point was mid radius and it also moved that point of radius up 2cm (ex 2).

Which one (ex 1 or ex 2) would move the wrist farther up?
Which one (ex 1 or ex 2) would have greater mechanical advantage?

ex 1 would move the wrist farther up

ex 2 since the force is farther out (even though you'd technically want the force father out than the resistance).


Would a longer or shorter lever arm create more angular excursion of a joint during a muscle contraction?

Contraction of a muscle with a SHORTER lever arm produces a LARGER joint angular excursion than the same contraction in a muscle with a longer lever arm (even though a larger lever arm gives you greater mechanical advantage).



Which fibers are slow twitch?
Which fibers are fast twitch?

How do you remember?

Can you train fibers to change?

Type I
Type II (sub categories of A and B)

Type II is faster than Type I, and B is faster than A

Type II A can go to Type I or to Type II B. But outside of that, Type I can't become II and II can't become I.


Larger CSA (cross sectional area) of a muscle will produce more or less force?

T or F: The more fibers a muscle has, the larger its maximum force of contraction

Would pennate or parallel muscle fibers produce more force?





Which position of your arm will allow you to create the greatest amount of force/tension:

1) Arm is fully extended
2) Arm flexed at 90 degrees
3) Arm fully flexed

WHY? Explain ...

Arm at 90 degrees.

Think of the myosin and actin. If it is fully extended, there is not much crossbridging happening because sarcomeres are so spread out. Similarly, when arm is fully flexed, all the myosin and actin are already interacting and there is nowhere they can continue to crossbridge and slide. At 90 degrees is optimal where sarcomere is in resting position and the maximal amount of cross bridges (thus tension and force) can happen.


What is the resting length of a muscle?

The point where sarcomere is relaxed, the actin/myosin are not too stetched and elongated, or too condensed / crossbridged and bunched together.


Describe the curve / graph of what you'd see if you got a fully flexed/shortened muscle and slowly stretched it out until it ruptures. How would that curve look if the x axis is length of muscle, and y axis is tension?

As muscle starts all bunched up and flexed, there is little tension (as explained above). But as you keep slowly pulling it, the tension increases. Once you get to about 90 degress (or resting length) then tension is at its max. Once you go past the 90 degrees, the muscle tension actually decreases because now you are elongating the sarcomeres (as described in the last flashcard). But as you pull and pull and pull, getting closer to a tear, the tension will actually go back up.


Related to the last flashcard, how would the curve of the ligament look?

With arm flexed up, lig is very slack. But at the point where muscle starts to max out tension (90 degrees resting potential) then the ligament starts to activate and gets more and more tension the more you lengthen muscle ... up to the point of rupture.


Explain the length-tension relationship of muscle

Max tension of a muscle is where / at what point?

Described above ... but tension is weak when arm / muscle is flexed, but as you start to stretch/elongate/lengthen it - when you get to resting length (or 90 degrees where actin and myosin can do most crossbridging) you get the most tension.

At the resting length or 90 degrees flexion.


I didn't fully get this point, but in these joint connections we have SERIES ELASTIC components (tendons joining to bones on either end) and in the middle are PARALLEL ELASTIC components (the connective tissues like epi and perimysium). Also working in this chain of elasticity of muscle contraction is the actin/myosin crossbridging.



Explain difference between Active Insufficiency vs. Passive Insufficiency:


Active: When AGONIST muscles can't shorten any more (with/over 2 joint muscles). The muscle can NOT contract any more cause crossbridges are all bunched up.

Passive: When ANTAGONIST muscle can't elongate/stretch any more (with/over two joint muscles). The muscle can NOT stretch any more because all the crossbridges have been stretched too far.

- Active: Flex wrist down as far as you can, or lift thigh up extending hip while trying to keep knee extended.
- Passive: Extend wrist all the way back, or bend over and flex hip while keeping knee extended to stretch hamstrings.

*** Active Insufficiency. When a muscle cannot shorten anymore, occurs with the agonist. Passive Insufficiency. When a muscle cannot stretch anymore, occurs with the antagonist.


Does your mechanical advantage increase if the distance from joint to muscle force is increased or decreased?

A muscle's lever arm is maximum when the muscle angle is what:

When a muscle is in its most lengthened position, its angle of application (and hence its lever arm) is close to ________


90 degrees



Explain the difference between spurt and shunt muscles (and give examples):

Spurt: Gives a spurt or movement. Biceps contracting provides spurt or movement. It produces movement around a joint. Ex: biceps

Shunt: It shunts or tries to compress. Instead of providing movement (like biceps), it helps protect joint to avoid dislocation. It provides stabilization / compression at a joint to avoid bones being pulled apart. It's a muscle that, rather than producing observable motion, contracts to resist dislocating forces occurring at joints, the coracobrachialis, short head of biceps, and long head of triceps all contract to resist downward dislocating forces at the shoulder joint, as when toting luggage. Ex: brachioradialis, brachialis.


There are 3 types of muscle contractions. What are they - explain:

- Concentric: Agonist muscle flexes / contracts
- Eccentric: Agonist muscle extends / relaxes / lengthens

- Isometric: muscle contracts without lengthening or shortening (static contraction)

- Muscle contractions (or joint) move at the same speed


Explain difference between these:

- Agonist
- Antagonist
- Synergist

If we abducted our arm up, what is agonist, antagonist, and synergist

If we extended knee, what is agonist, antagonist, and synergist

- Agonist: Primary muscle moving
- Antagonist: Opposes agnonist
- Synergist: muscle that works with and helps agonist, or stabilize a joint so agonist can work

Abduct arm:
- Agonist: deltoid and suprspinatus
- Antagonist: subscapularis, infraspinatus, teres minor (maybe even pec major, lats, teres major)
- Synergist: biceps, other side of body m's to stabilize while I lift arm, erector spinae for lateral bending, hip abductors on opp. side.

Extend Knee:
- Agonist: quads
- Antagonist: hamstrings
- Synergist: glut med/min to stabilize, back m's to stabilize


1) What is the length load velocity curve? Explain it:
2) If I have 0 velocity, what type of contraction is it?
3) Positive velocity would be what type of contraction?
4) Negative velocity would be what type of contraction?
5) The faster a muscle shortens / contracts, or the faster the velocity of contraction, will it produce more or less force? WHY?
6) The faster a muscle elongates, or the faster the negative velocity of elongation or eccentric movement, will it produce more or less force? WHY?
7) Will maximum isometric or maximum concentric contracting produce more force?
8) T or F: Speed of concentric contractions is inversely proportional to the force of concentric contractions
9) Positive velocity on the length load velocity curve is eccentric movements?


2) Isometric
3) Concentric
4) Eccentric
5) Less. Why: if I go fast through a contraction, I can't recruit more motor units. If I go slower, I can attract more motor units and thus fire up more muscle fibers to help.
6) More. To a point.
7) Isometric
8) True
9) False. It is concentric. Eccentric is negative velocity.


From the last slide, let's look at a real example.

If a weight lifter did biceps curls and lifted 10 lbs on the first set, but then did 50 lbs on the next set, which set would he be able to do the curls fastest?

The 10 lb set obviously allows him to do the curls faster. Why?

Because the FASTER the velocity of a concentric movement, the LESS load or force you can generate. But the slower the velocity (50lbs), the more load/force you can generate.


What is the sequence of muscle twitches:

Explain fused tetnus:

Twitch > paired twitch > unfused tetnus > fused tetnus

Fused tetanus – action potentials are firing quick enough that muscle doesn’t have enough time to relax.


What other factors besides velocity of concentric contraction will impact the force generating capacity of a muscle:

- Age
- Gender
- Health and condition of individual
- CSA of type of muscle


Is the CSA of muscles more or less with men compared to females


"No significant difference between sexes was observed when strength was expressed per unit of muscle CSA (F.CSA-1) for the elbow flexors and extensors. However, the men showed significantly higher F.CSA-1 than the women for the knee flexors and extensors (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)."


Explain role and difference between muscle spindles and golgi tendon organs:

Are both muscle spindle fibers and golgi tendon organs proprioceptors?

What are proprioceptors:

Do both have sensory (afferent) and motor (efferent) fibers?

Muscle Spindles: Muscle spindles are sensory receptors within the body of a muscle that primarily detect changes in the length of the muscle. It is the stretch reflex that senses muscle lengthening and speed of lengthening and thus protects muscles from stretching too far.

Golgi Tendon Organs: These are also proprioceptors that sense too much TENSION in a tendon. It protects muscles from taking on too much load/tension and shuts muscle down if too much.

YES, both are.

Proprioceptors = help you know or sense where you are
in space.

Muscle spindles have both, but golgi tendon's don't have a motor part - the nervous system just stops or shuts down that muscle.


What are joint receptors:

4 Examples of Joint receptors:

Are there joint receptors in articular cartilage?

Proprioceptors in the joint ... they are like the muscle spindles and golgi tendon organs of muscles, but these are in the joints. These receptors will sense too much stretch or load (or speed of stretch) within a joint.

4 Examples:
- Golgi-Mazzoni Corpuscles
- Pacinian Corpuscles
- Golgi ligament endings
- Free nerve endings



What is Hilton's Law:

(how to remember)

Hilton’s Law: If a muscle crosses a joint, the nerve supplying that muscle also sends a sensory branch to the joint.

(Remember: the nerve of Paris Hilton to cross over the line)


On exam, I did NOT know about component motion.

What is it?

?? I don't know, but I think it is the motion AT THE JOINT (arthrokinetics). But double check, not sure.