Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

YEAR 3 > Biomechanics > Flashcards

Biomechanics Flashcards

1
Q

What are kinetic forces?

A

Forces acting on an object/ the body responsible for casing or maintaining stationary position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do force platforms do

A
  • Ground reaction force is the most common force measured by force plate
  • Measured force acting on performer has the same magnitude as the reaction force exerted on the performer by force plate by in the opposite direction
  • Force platforms incorporate a force transducer (strain gauge of pizoelectic) which converts the force into an electric signal
  • Signals from transducers are amplified and sometimes modified
  • Converted to digital signals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Name the 2 types of force plate

A

Piezo electric (Kistler) and Strain Guage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain how a piezo electric force plate works

A

Contains crystals which change electrical charge depending on the force applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the advantages and disadvantages of a pizo electric force plate

A

:) Sensitive to rapid changes in force

:( Temperature sensitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain how a strain gauge force platform works

A

Contains beams which bend depending on the force applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the advantages and disadvantages of a strain gauge force platform

A

:) Stable over long times, cost

:( Slower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Name the main system requirements for a force platform

A 
Linearity 
Rigitidy 
Range
Cross talk 
Sensitivity 
Hysteresis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the force platform outputs

A

Forces in 3 dimensions: vertical, anterior-posterior, medio lateral

  • Rate of force development –> slope of force time trace
  • Impulse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the uses of force platforms

A 
Gait analysis 
Shoe research 
Training 
Rehab 
Impulse in take off
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When does hysteresis exist

A

When the input output relationship depends on whether the input force in increasing or decreasing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What should the range be for a force platform

A

Range of forces that can be measured must be adequate for the application and the range should be adjustable

If the range is too small for the forces being measured, the output voltage will strata

Ranges usually -10 to 10kN for the 2 horizontal aces and -10 to +20 kN for the vertical axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain sensitivity in terms of force plates

A

=the change in the recorded signal for a unit change in the force input of the slop of the idealised linear voltage force relationship

Sensitivity decreases with increasing range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is cross talk

A

Force plates normally measure force components in more than one direction

The possibility then exists of forces in one component direction affecting the forces recorded by the transducers used for by the other components

Cross talk= the interference between the recording channels for the various force components

-Cross talk must be small, preferably less than 3% of full scale deflection[;;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Name the stages in qualitative analysis

A

Preparation
Observation
Evaluation
Intervention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does preparation involve in qualitative analysis

A

Development of theoretic model of the most effective technique
Indentify goal and factors which affect the outcome
Knowledge of the performers
Biomechanics factors that affect performance
Split the activity down to several phases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does observation involve in qualitative analysis

A
  • Selection of critical features to observe
  • Selection of appropriate number of trials/observers
  • Consider number and experience of observers
  • Selection of appropriate viewing distance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does evaluation involve in qualitative analysis

A

-Errors corrected in the order that generates the most improvement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does intervention involve in qualitative analysis

A

Feedback and instruction to the performer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is semi quantitative analysis

A

Same as qualitative but with some simple measurements such as simple joint angles

Can give more detailed comparisons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Name quantitative kinematic methods

A 
video
high speed cinematography
ultrasound
gyroscopic sensors
Electrogoniometry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Name quantiative kinetic analysis methods

A

Force plates
Pressure transducers
Electromyogrpahy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the 2 requirements to measure kinematic parameters

A

Accurate measurement of the position the centre of rotation of each of the moving body segments

An accurate time measurement for each position measurement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the problems with 3D and 2D

A

Need to see all joints from all angles simultaneously - cameras need to be synchronised which is expensive and time consuming g

Optical errors

Time measurement

How to get real life size co ordinates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Advantages and disadvantages of video
:) Immediate feedback (but not with computer digitizing) Standardization High Shutter Speeds (up to 1/8000 sec) Digital Technology (CCD/CMOS chips and DV/DVD or memory card) Quality - HD Cost :( Genlocking 'Rolling' shutters now on most consumer HD cameras Speed limited to 25 or 50Hz (pictures/second in UK) [30/60 Hz in USA] on most cheap systems (some up to 1000 Hz with reduced resolution). Full resolution >50/60 Hz expensive Errors involved in manual digitization can be high (without markers and/or in competition)
26
Advantages and disadvantages of opto electronic
:) Fast collection Immediate feedback (<30 secs) Software already written Fast (up to 1000Hz (pictures/sec) with shutters up to 1/8000s) Tracking markers can be very accurate (small errors) no need for digitising once set up, can use for multiple participants :( Markers required (not competition) - not on joint centres but on skin. Cost (usually need at least 6 cameras = >E50k) Calibration? Markers crossing cause confusion (depends on software) Low levels of light needed Set-up time to position cameras to see all markers all the time
27
Advtanges and disadvantages of 16mm cinematography
:) Fast (up to 10000 Hz pictures/sec) - most cameras up to 500Hz Very high quality image Timing lights built-in (you know camera speed exactly) High speed shutters Easier to synchronize - link cameras directly :( Delayed feedback Cost Filming 'blind' - limited viewfinder. High light levels needed (Daylight) Availability of film and processing - VERY rare? Not mains powered - need a large battery and charger Errors involved in manual digitization can be high
28
Advantages and disadvantages of inertial sensors
:) Fast Collection & Easy Setup Immediate feedback Software already written — 'plug and play' No cameras needed so no problems with field of view Wireless (advanced system) so no leads Basic electronic sensors cheap :( Cost - Systems expensive z E30000-E40000 (Xsens) 'Drift' - Speed of sampling (how many data/points per second) depends on the number of sensors used. Sensor are z size of matchbox and have to be strapped on with belts or suits.
29
Advantages and disadvantages of electrogoniometry
:)Gives joint angles directly Cost (cheap) Simple Easy to interface to computer - fast data collection and analysis ``` :( Difficult to get limb exact position in space - no fixed reference frame, because only angles are measured Restrict movement Usually used only on up to 3 joints. ```
30
What is filming speed?
How many pictures per second camera records(frames) Each video picture is made up of 2 fields interlaced Film speed is usually 25 frames per second
31
What is shutter speed?
length of time when the film or digital sensor inside the camera is exposed to light,
32
What does it mean if the shutter speed is set at 1/1000
the camera will not 'see' anything for 0.019s out of 0.020s in each field This will freeze the action for each field
33
What is the best shutter speed for fast sporting actions
very short - maybe 1/4000
34
What is the problem with light for short shutter times
Only exposes the film to light for a very short time in each picture which means not much light can get onto the film --> dark
35
What are the procedures for 2D kinematic data collection
Procedures for 2D kinematic data collection Mount camera stationary on tripod (no pan/tilt) Action fits in field of view (including clubs/rackets/jumps etc) Unhindered subject performance Zoom lenses best (reduce perspective error) Performer moves at 90 degrees to optical axis of camera Calibration lengths and vertical reference needed Contrasting joint centre markers (Careful) Suitable frame rate (8-10 times fastest action frequency - week 4) Good lighting (Daylight best). Use floodlights if inside or dark Trial/subject information should be recorded
36
What is accuracy
the difference between an observed value and the true value
37
What is precision
The variation in measurements that you would expect to be the same
38
What is resolution
finest with which a measurement can be made
39
What are systematic errors
Errors that stay the same from video field to field E.g camera not running at the correct speed
40
What are random erros
Errors that vary from field to field Spiky on a graph E.g joint markers moving out of a plane
41
What is a fourier transform used for
to transform position time information to frequency data split analysis into 2 sections (less or more than 12Hz) identify section of noise and remove it truncated = all info above a particular frequency can be removed
42
What is frequency spectrum
When a tourer transform has been performed, the amount of information present at each frequency is available which is called frequency spectrum
43
What is filtering
One way of smoothing reduces the data above a certain frequency but doesn't completely remove them filters can be non recursive (simple) or recursive( some of the already filtered data used to make each point more accurate) E.g butterworts filter
44
What is spline smoothing
most efficient way of smoothing a curve equation is fitted between all points or even each point. This can be a Cubic or Quintic spline - the curve fitted used x3 or x5 to 'best fit' the line between points generate pathway which best describes all points
45
What is inverse dynamics
We can use the displacement, velocity , acceleration to get the forces, moments, energy, power etc
46
What are kinetograms
stick figures | movement patters
47
When would be most appropriate to use a short shutter speed?
fast sporting actions | need lots of lights
48
What should the frame rate be for slow motion
high
49
If the shutter speed of a camera is set at 1/1000, how long won't the camera 'see' anything for out of 0.020 seconds
0.019s
50
What would you do if the cameras can't be genlocked?
the two dimensional co ordinates obtained from each of the camera views must be synchronised by interpolating the data and then shifting one data set by the time lag between the 2 shutters
51
What are CCDs and CMOSs
Sensors in cameras controlled by the shutter CCD is the most common type CMOS has less power
52
How does gen locking take place?
Physically linked the cameras with a gen lock cable
53
What is a co ordinate digitiser used for?
To undertake quantitative analysis | Device enables 2D co ordinate of specific points on the video image such as anatomical landmarks to be recorded
54
What does resolution refer to?
the minimum separation between two points on the screen that the system is able to detect
55
What is an increased frame rate important for?
to improve the precision and therefore the accuracy of temporal measurements this is particularly important where the phases are of short duration such as the hitting phase of a tennis serve
56
suggested frame rates for walking and swimming
25-50Hz
57
Suggested frame rates for running and high jump
50-100 Hz
58
suggested frame rates of sprinting and a football kick
100-200 Hz
59
suggested frame rates for tennis serve or golf swing
200-500Hz
60
What is simi used for?
Digitising | the process of obtaining 2 dimensional co ordinates of specified landmarks on the performer from a video
61
Why is smoothing used
to remove the high frequency noise introduced by the digitising process - split fitting and fourier series truncation
62
What happens when there is a failure to smooth co ordinates sufficiently
lead to high levels of noise
63
What is the linear displacement of a body landmark
the change in the relevant scaled co ordinate of that landmark during a specified time period
64
what is perspective error
brains expect closer objects to appear larger than those far away
65
When does hysteresis exist
when the input output relationship depends on whether the input force is increasing or decreasing E.g an be caused by the presence of deforming mechanical elements in the force transducers
66
What should the range be for a force platform
must be adequate for the application range too small for the forces being measured ---> output voltage will saturate Suitable maximum ranges for many sports biomechanics applications would be -10 to +10kn
67
what is sensitivity
the change in the recorded signal for a unit change in the force input or the slope of the idealised linear voltage force relationship sensitivity decreases with increasing range
68
what is cross talk
possibility of forces in one component direction affecting the forces recorded b the transducers for the other components cross talk expresses this interferes cross talk should be less that 3 % of full scale defection
69
why is it important that force plate systems are calibrated
to minimise systematic errors
70
what are the limitations of smoothing
if there are mixed frequencies, smoothing routines have to be available for each point separately
71
What should be done to overcome the issue of errors usually being at the ends of the data
take more data than you need e.g 10 frames before an 10 frames after action of interest
72
what are the implications of force plate analysis
measurements of forces applied by an athlete can aid a coach to quantitatively evaluate an athletes execution of a skill E.g data of the forces applied to the ground in a vertical jump provide a picture of the explosive abilities of the athlete
73
name the different plates force platforms produce data for
vertical anterior-posterior medial lateral

YEAR 3 (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions