other measurment systems Flashcards
In 3D motion capture (e.g. Vicon) what factors could affect accuracy of marker tracking. (4 marks)
The number and positioning of cameras, the closer to the movement the more accurate, but if too close marker can go out of field of view. The more cameras the more accurate as movement is less likely to be missed.
Other reflective surfaces can be recognized as markers confusing the system and affecting accuracy of data collected.
External light can also confuse the system.
the Marker placemtn/location if incorrect influcnes accuracy of motion capture.
A Pedobarograph can be used to measure pressure during gait. State the equation used to calculate pressure and explain what information you can obtain from Pedobarograph results that you cannot get from a force platform. (3 marks)
Pressure = force / area (N/m)
Pedobarograph gives a specific distribution of force/pressure across the whole foot, a force plate only gives the centre of pressure location.
19) Isokinetic dynamometers are widely used by football clubs for ‘medicals’ when screening potential new players. Critique the use of this approach by providing a total of three advantages and disadvantages (you may include three advantages, three disadvantages, or a combination of advantages and disadvantages). (3 marks)
reliable accurate data, strong internal validity due to lab design,
can be used effectively to risk asses through analysis of imbalances in muscles.
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No ecological validity, isolated to one plane of motion at a time, sporting movements go through a range of force velocity, and sporting factors like forces to overcome a football apon contact cannot be replicated
A Pedobarograph can be used to measure pressure during gait. State the equation used to calculate pressure and describe the path of the centre of pressure across the sole of the foot during typical heel to toe gait (3 marks).
Pressure = force/area.
· The CoP starts at the lateral aspect of the heel moves anteriorly and medially as the foot moves through pronation.
· As the forefoot makes contact, the foot moves into supination and the CoP continues anteriorly with some degree of lateral movement.
Pas through between 1st and 2nd toe.
What is inside IMU’s?
accelerometer, gyroscope, and magetometer.
What 2 types of IMU systems are there, and what are the advantages and disadvantages?
There is complete IMU systems, (Xsens), and standalone sensors (VIcon).
Complete systems allows easy setup, data visualisation and straightforward data processing.
- limited set up specified by the manufacturer,
- processing is according to manufacturers design too.
- costly
What do IMU’s measure and units?
acceleration (m.s2), angular velocity (deg/s), magnetfic field strength (MicroT),
Why is calibration important in IMU?
For data recording to be accurate, we calibrate to remove sensor bias from the magnetometer and minimise any influence from external factors.
Like magnetic fields from metals, and other devices/electrical currents. (Hence must be calibrated in new environments).
Why is an IMU useful?
IMU’s give daa about acceleration, velocity adn movement oreintation/direction. they have been used to measure impacts and loads in collision sports ti improve safety and performance.
collect motion data that can be used in calculating estimates of work, speed, and even movement angles
When comapring 3d analysis to 2d, what are some pros and cons?
Pros,
+3d removes errors seen in 2d analysis, minimises human error.
+more accurate and faster processing speeds,
+allows capture of movements in multiple plans of motion, which is difficult in 2d. e.g shoulder with 6 of.
-No video of the actual momvment, raw data lost
-complex set up and use.
-limited environment and marker related error
-expensive!
What information can vicon 3d systems give?
GRFs, kinematics and kinetrics, we can trim motion specifically to what we want, we can reconrstruct markers in 3d space.
What is the equation for torque and what other information does a isokineticdynometer give?
Torque (Nm) = Force (n) * lever arm (m),
infromation regarding the relationship between a joint angle and torque, and between antagonist muscle pairs.
What are some applications for isokineticdyonmeters?
Isokinetic.. can measure muscle strength in a controlled, isolated and reliable measurements.
(-by stabilising other body parts, using plane of motion in interest and it is easily repeatable).
Can be used in rehab and for assessment of injury risk.
injury prevention and training interventions (strength).
what are limiations to isokenetic…?
lacks ecological validity, isolated to one joint at a time, can be less accurate from velocity overshoot(initial velocity kick),.
What can pedobarographs show?
gait anlaysis, regions of the foot with the most pressure, cop path, foot orientation and foot type when static,
can measure stability, static and dynamic balance.
