MEASUREMENT

Question 1

Frame rate

Answer 1

How many individual frames are created each second

Question 2

Shutter speed

Answer 2

How long each individual frame is exposed for

Question 3

Intra participant variability

Answer 3

Variability within participants

Question 4

Inter participant variability

Answer 4

Variability between participants

Question 5

Intra observer variability

Answer 5

Variability in measurement or observation methods of single (within) researcher.

Question 6

Inter observer variability

Answer 6

Variability in measurement or observation methods between multiple researchers.

Question 7

Retroflective

Answer 7

A device or surface that reflects light back to its source with a minimum of scattering

Question 8

High speed camera

Answer 8

A device capable of capturing moving images with exposures of less than 1/1,000 second or frame rates in excess of 250 frames per second.

Question 9

Slow motion

Answer 9

The action of viewing video more slowly than it was made or recorded, so that the action appears much slower than in real life

Question 10

What is stereo photogrammetry in movement analysis

Answer 10

“two”, photogrammetry: “photographic measurement”

Question 11

List three limitations of stereo photogrammetry:

Answer 11

• Camera perspective: Markers / body locations can easily be obscured from view
• Marker identification (e.g. manual):Random error via subjective marker identification / Error prone to propagation as error exists in both camera images before position triangulation
• Difficult to model body segments in three-dimensions (due to above); limited use in biomechanical applications

Question 12

List the two mains methods for calibrating stereo photogrammetry systems

Answer 12

• Checkerboard

* Calibration frame

Question 13

Three-dimensional motion capture systems are an alternative data capture system to stereo photogrammetry, but what is it?

Answer 13

Three-dimensional motion capture systems are an alternative data capture system to stereo photogrammetry, but what is it?

Question 14

What are depth cameras?

Answer 14

Consumer technology capable of three-dimensional measurement ‘out-of-the-box’
Low-cost (~£150) and easy-to-use
Depth information (structured light or time-of-flight) for each pixel (e.g. 2D and depth)

Question 15

Why should we ensure that any 3D data captured systems is synchronised?

Answer 15

To ensure data captured from different sources reflect the same instant in time (i.e. measurements are synchronised)

Question 16

How many individual frames are created each second.

Answer 16

frame rate

Question 17

How long each individual frame is exposed for.

Answer 17

shutter speed

Question 18

Variability within participants

Answer 18

inter observer variability

Question 19

Variability between participants

Answer 19

intra observer variability

Question 20

Variability in measurement or observation methods of single (within) researcher.

Answer 20

Intra participant variability

Question 21

Variability in measurement or observation methods between multiple researchers.

Answer 21

Inter participant variability

Question 22

A device or surface that reflects light back to its source with a minimum of scattering

Answer 22

Inter participant variability

Question 23

A device capable of capturing moving images with exposures of less than 1/1,000 second or frame rates in excess of 250 frames per second.

Answer 23

high speed

Question 24

The action of viewing video more slowly than it was made or recorded, so that the action appears much slower than in real life.

Answer 24

slow motion

Question 25

what are requisites of data captured in sport and exercise?

Answer 25

accuracy
validity
precision or reliability
objectivity
minimal error propagation
comprehensibility

Question 26

define logical validity

Answer 26

(also known as face validity) – when this is obvious

Question 27

define criterion validity

Answer 27

validate measures against accepted test or
measurement standard (the criterion)

Question 28

define concurrent validity

Answer 28

when two measurements are taken simultaneously

Question 29

define external validity

Answer 29

the extent to which measurements emulate the real

world (see Brunswick, 1956 for review of ecological dynamics)

Question 30

define reliability

Answer 30

Expresses the consistency of a test or measurement over time

Question 31

define repeatability

Answer 31

how well an individual can repeat an experiment (e.g. intra-observer)

Question 32

define reproducible

Answer 32

: how well an experiment can be reproduced (e.g. inter-observer)

Question 33

define consistency

Answer 33

A reliable measurement can support validity: reliability is essential for validity

Question 34

state some examples of human impacts

Answer 34

blunt force trauma, infrequent or high-force inmpacts such as commotio cordis in baseball.

Or chronic, repetitive loading the accumilation of low force impacts. e.g. medial tibial stress syndrome in running.

Question 35

name some devices that measure human impacts.

Answer 35

force platforms and load cells.
pressure platforms
isokinetic dynamoeter.

An an indrect measure of human impacts can be by usiing an accelerometer.

Question 36

Why is impact effected by inertia?

Answer 36

This is because the heavier the object the more resistant it is to having its motion changed. Mass is an intrinsic property and does not change or depend on what it is around (unlike weight it depends on gravitaional pull towards the centre of the earth).

Therefore the result of an impact depends on it’s inertia and initial momentum of both objects (assuming an inelastic impact).

Then during impacts we typically measure reaction force obtained by one of the objects. This accounts for Newtons thrid law.

Question 37

How are impacts measured?

Answer 37

Newton’s third law. Reaction force.

Question 38

What is dynamic friction?

Answer 38

Kinetic friction, also known as dynamic friction or sliding friction, occurs when two objects are moving relative to each other and rub together (like a sled on the ground).

Question 39

How are impacts interpreted?

Answer 39

Vector quantities such as magnitude and direction.

Question 40

State the mechanical derivatives that can also provide other ways of characterising impacts.

Answer 40

Acceleration- e.g. in tennis by measuring the impact acceleration that the racket endures this can help to identify the rackets sweet spot. This impact will be shown through vibrations. So we can use an accelerometer as an indirect measure of force to understand the impact force produced.

another example is zepp tennis which is a triaxial gyroscope and dual accelerometer.

Acceleration can also be used as a mechanical derivative to characterise head impacts. Such as the head impacts of CTD headform. This impact acceleration can then be used to design/re-design the properties of helmets. e.g. head impact crtierion HIC.

velcoity

momentum

impulse

energy

power