Lecture 10, Classifying Motion

Question 1

Angular Motion (what are the three types of angular movements?)

Answer 1

• angular motion occurs when a body moves along a circular path, revolving around a central line or point
• angular motion is also referred to as rotation
• there are three types of angular movements or rotations
  ◦ yaw: rotating to the left or
  right
  ◦ pitch: rotating up or down
  ◦ roll: tilting to the left or right
• can never keep the three types of angular movements straight
• all angular movements are going to occur about the axis of rotation/pivot point - pen (fixed around plane of movement - paper) - how the paper or pen are aligned changes according to the type of angular movement

Question 2

Angular Motion (Internal and External)

Answer 2

unlike translation, angular motion keeps to a fixed point called the axis of rotation (all based on where it is located - inside body or outside)

external axis of rotation
- imaginary line found outside of the body
- system moves in a circular path around the axis
- rotating with respect to the environment (axis of rotation outside of body - hand with respect to the ground)

internal axis of rotation
- imaginary line found inside of the body
- system moves in a circular path around the axis
- as you lift your arm away from body you are rotating away from axis of rotation away from your body

Question 3

Anatomical Reference Position

Answer 3

it can be difficult to identify body parts and positions since joints are freely moveable
- commonly used reference position of the human body is called anatomical position
◦ body is erect
◦ facing forward
◦ feet aligned parallel to each
other
◦ toes forward
◦ arms hanging straight below
shoulders
◦ fingers extended
◦ palms facing forward
- anatomical position is the standard reference position for the body when we describe locations, positions, or movements of the body
- all rotations are described from the anatomical position
- does not matter how you are oriented or located but it is just that we can have a common language when referring to the body (inferior, medial, superior, posterior, anterior etc.)

Question 4

Cardial Plane

Answer 4

a plane that passes through the midpoint or centre of gravity of the body
- the plane may be useful for locating anatomical structures
- the planes are also helpful for describing limb movements
- movements occur as rotations of the limbs
- rotations occur around an axes and within specific planes
- each plane of movement has a corresponding axis of rotation
- 3 planes that cut the body up and divide it into different segments

Question 5

What does the cardinal frontal plane divide into?

Answer 5

front and back halves

Question 6

Types of Angular Motion

Answer 6

an have a combination of two different angular movements at once neck is axis of rotation and plane of movement is head
- turn to the left or right (spin to left or right) - YAW - to rotate around a vertical axis - going along long part of body (longitudinal) - transverse
- to look up and down - PITCH - rotate around a mediolateral axis (sagittal)
- till the head to the left or right shoulder - ROLL - to rotate about an anterioposterior axis (frontal)

Question 7

Reference Planes and Axes (sagittal plane and mediolateral axis)

Answer 7

the sagittal plane: divides the body into left and right segments

the mediolateral axis: runs towards and away from the midline
- flexion is an example of sagittal plane action (any movement parallel to the plane that does not cross it) and extension is also an example (when you go beyond anatomical position is hyper extension is also an example of sagittal plane action or movement around a mediolateral axis)
- what movements would occur in this plane? flexion/extension, hypertension

Question 8

Reference Planes and Axes (frontal plane and anterioposterior axis)

Answer 8

the frontal plane: divides the body into front and back segments

the anterioposterior axis: towards front and back of the body
what movements would occur in this plane?
- abduction (away from the body) or adduction are examples of frontal plane movement or around the anteriorposterior axis
- elevation and depression (as you lift scapula up and down)
- lateral flexion (off to left or right)
- all examples of roll above
- any movement that is occurring in parallel but is not crossing the plane

Question 9

Reference Planes and Axes (transverse (horizontal) plane and longitudinal axis)

Answer 9

the transverse (horizontal) plane: divides the body into top and bottom segments

the longitudinal axis: along the long part of the system
- medial (towards the midline) and lateral rotation - for example bringing arm into the body
- supination (open up your palms) and pronation (bring palms down)
- yaw are all under this

Question 10

Which of the following motions occurs primarily in the frontal plane?
- running
- cartwheel
- pirouette
- all of the choices are correct

Answer 10

cartwheel

Question 11

Analyzing Motion

Answer 11

reflective markers are placed on the body in a fixed position
high-speed cameras are used to capture movement
this technique, called video motion analysis, can be used for gait analysis, sport relays, and to measure performance
- how far they rotate, how fast they rotate and whether they are rotating at the exact same rate or not
- by knowing the position of the markers you can know how they are moving

Question 12

Analysis Motion (2)

Answer 12

Once you know the position of a joint or body segment, you can measure: change in position, the speed of motion, and changes in the state of motion
- looking at specific points on the soccer player - take the person and turn them into a stick figure - landmark certain spots on body and then connect them until you have 3 points where 2 lines give you a connection where you want to measure how much space there is between lines where they connect

Question 13

Defining Angles

Answer 13

the space between two intersecting lines or surfaces at or close to the point where they meet
angle is used to designate the measure of angular position or of a rotation
- two lines that form a connection and how space there is between those two lines
- do not care how you measure if but you need to be consistent each team

Question 14

Identifying Angles (what do we need to know?)

Answer 14

if we wanted to identify the angle at the elbow joint, what information would we require first?
- we need to: identify the location of three joints centres of rotation (instant centre), identify the orientation of the 2 longitudinal segments where 3 joint centres and 2 longitudinal segments will identify 1 joint angle
- need to know 3 points (instant centre - where movement occurs from): 3 points from movement occurs from which gives 2 lines which gives us one part of the body (we can measure - how far, fast and whether it is moving at the same rate or not) identify the location of three joint venters of rotation

Question 15

Defining Angles - Relative Angle

Answer 15

a relative angle is the space between the longitudinal axes of adjacent segments (ex. the angle at a joint)
- relative means it is specific to the thing that you are measuring
- measuring two things that are connected - in contact, physically touching or just resting on each other (the angle that the upper arm makes with the forearm for example)
- the angle formed inside the joint is the internal angle (what closes up) - the inside space (anterior side of elbow and the backside would be the exterior whereas it would be opposite for the knee)
- the angle is formed on the exterior surface of the joint is the external angle (opens up) - larger space (the spot that remains)

Question 16

Defining Angles (Absolute angle)

Answer 16

an absolute angle is the space between a body segment with respect to a fixed line of reference
- measurement of one real thing and one thing that does not exist but it is common to everyone one of us (we always need two things connected but it does not need to be real)
- measurement between one body part you are interested in and reference it to either the horizontal or vertical axis (cartesian coordinate system)
- an angle measurement between the longitudinal segment and the x-axis
- an angle measured between the longitudinal segment and the y-axis
- reference the thing you are interested in to the vertical or horizontal axis (does not matter which one you better but it needs to be consistent - everything must be vertical or horizontal)

Question 17

Which method is better when measuring angles?
- using relative angles
- using absolute angles
- depends on the situation

Answer 17

depends on the situation

Question 18

Angular Kinematic Units - what is a degree (°)?

Answer 18

• common method for measuring angles
• an arbitrary unit of measurement
• useful to ancient astronomers
• once around the circle is 0° to 360°

Question 19

Angular Kinematic Units - what is a revolution (rev)?

Answer 19

• simple and natural measurement
• once around the circle
• 1 full turn
  (can visualize better than degrees)

Question 20

Angular Kinematic Units - what is a radian () dimesionless or (rad)?

Answer 20

• the 3 lines are the exact same length for the radian (a line from centre of circle to the outside, a line on the outside of the circle on the curve which is the exact same length and then another line back to the centre)
• angle is 57.3 degrees when all 3 sides are equal
• radian is a ratio or relationship between two things: angular measurement in degrees and linear measurement of the lines (length of the lines)
• dimensionless and unitless
• we use units rad
• pi is 3.14

Question 21

Which of the following is the standard unit of measure for angular variables when measuring human movement?
- degrees
- radians
- revolutions
- all the above are acceptable units of measure

Answer 21

all the above are acceptable units of measure
*important thing is to be consistent but there is a time in which when we equate linear and angular stuff together we have to measure in radians (general motion)

Question 22

Converting Between Units

Answer 22

it is important to know how to convert from one unit to another
- 360° = 1 revolution
- 1 revolution = 2𝜋 rad
- 2𝜋 rad = 360°
- 57.3° = 1 rad (if you draw the 3 lines the angle will always be 57.3)
- need to know how to go from one form to the other

Question 23

Measuring Angles

Answer 23

• a goniometer is an instrument that measures an angle - gonia (angle) metron (measure)
  basic goniometer: useful for measuring angles in pictures and static analysis - something frozen in time and make simple measurements

electrogoniometer: taking measurements during movement and dynamic analysis - when someone is running around (use a wire that sends around an electrical signal when the resistance in the wire changes we can transduce that into how much of an angular change there was) - as you move in real time you can measure how much space there was in your movement

• widely used in physical therapy to assess range of motion before and after intervention (tracking progress over time) - see if you are improving

Question 24

Measuring Body Angles

Answer 24

the axis of rotation is usually in a fixed position - a door rotates in a fixed position around a hinge (the hinges are locked in place)
however, the axis of rotation at a joint is not fixed - the longitudinal segment shifts position because the axis migrates (allows you so much more movement, more range of motion because it is not held in place so much - shoulder) - our body is not as rigid as other objects so it makes it harder to figure our where the axis of rotation is
- when it comes to measuring angular stuff you cannot be precise and so you must estimate at times

Question 25

Measuring Body Angles (2)

Answer 25

• can you locate the elbow joint? the hip joint? the shoulder joint?
• how certain can you be of the precise location of the origin of movement (Instant Center - your best guess)?
• when analyzing human movements, we estimate the position of the axis of rotation
  ◦ the markers are not moving with the axis of rotation they are moving with the whole body
• the axis of rotation moves and is inside the body so we can never be fully sure

Question 26

Describing Angular Movement - angular distance and displacement

Answer 26

describing the object’s position (or location) in space
angular distance - scalar quantity
(Φ – phi pronounced fee)
- the total amount of rotation (do not care what which way you are moving in terms of direction) - changing orientation which can change regardless of a change in position or not

angular displacement - vector quantity (how far you rotated position and what way are going - left, right)
(ϴ - theta)
- the change in angular position (where you start and where you end)
units: degrees (°), revolutions (rev), or radians (rad)

Question 27

Describing Angular Movements - angular speed and angular velocity

Answer 27

describing the temporal patterns of movement (way of quantifying performance - good or bad)
angular speed - scalar quantity (number only)
(σ – Sigma)
change in angular distance / change in time
σ = (Φ2 – Φ1) / (t2 – t1)

angular velocity - vector quantity
(ω – Omega)
change in angular displacement (care about direction and magnitude) / change in time
ω = (ϴ2 - ϴ1) / (t2 – t1)
units: °/s, rev/s, or rad/s

Question 28

Describing Angular Movements - angular acceleration

Answer 28

dynamic motion is characterized by a change in angular velocity
torques produce a change in angular velocity (cause things to speed up or slow down)
angular acceleration - vector quantity
(α – alpha)
change in angular velocity / change in time
α = (ω2 – ω1) / (t2 – t1)
units: °/s2, rev/s2, or rad/s2
- going faster or slower, speeding up or slowing down
- torque is needed to be there
- sign: reflect what the change is (faster or slower) what is happening to velocity or reflect influence on system (torque where it is coming from and where is it going)
- reflect the direction of the torque that creates the acceleration or the change in angular velocity - only system for velocity and displacement (the sign only reflects the direction of the rotation

Question 29

What is the angular acceleration of the second hand on a clock after one complete revolution?
* 60°/s2
* 6°/s2
* 0°/s2
* need more information

Answer 29

0°/s2 (because it is a vector quantity which measure change in position over time because if you around once you come back to the same place because it is as if nothing happened - it has nothing to do with the changing velocity rather the fact that nothing happens in terms of displacement

Question 30

What do the signs in front of the displacement and velocity values tell us about human movement?

Answer 30

a man rotates +50°, what does the + sign mean? - does not mean that you are more or getting bigger

a woman swings a golf club at a rate of -1200°/s, what does the – sign mean? - does not mean you are slowing down, the direction of rotation and nothing to do with speed

• a man rotates +50°, the rotation occurs in a counterclockwise direction
• a woman swings a golf club at a rate of -1200°/s, the rotation occurs in a counterclockwise direction

Question 31

Vectors and Signs

Answer 31

positive values mean that the system is rotating counterclockwise
- starting at 30° and moving to 60°
- displacement = 30°

negative values mean that the system is rotating clockwise
- starting at 270° and moving to 200°
- displacement = -70°

Question 32

A bike wheel spins at a rate of +2500°/s2, what does the sign in front of the acceleration value mean?

Answer 32

positive sign can reflect direction of torque or what is happening to change in angular velocity (speed up or torque is pushing you in counterclockwise manner - CANNOT MEAN BOTH HAS TO BE ONE)

Question 33

If an object is rotating at -3.5 rev/s2, what is happening? (quiz or final)
- the object is rotating clockwise AND speeding up
- the object is rotating counterclockwise and slowing down
- neither A nor B is correct
- either A or B are correct

Answer 33

either A or B is correct
could refer to change in velocity or direction of torque (1 or the other - slowing down and clockwise)
- for displacement and velocity it only refers to the direction of the spin but for acceleration torque also comes into play (what is causing the movement which also has a sign in front of it)