Laboratory Biomechanical Assessment
Many of the events that occur during gait either can not be visualised or occur too quickly for the eye to see.
The measurement of motion without reference to the forces that are responsible for generating that motion. The kinematic variables that are used to describe motion are displacement, velocity and acceleration.
Methods of collecting kinematic data:
• optoelectronic systems - uses markers that are active (emit a light signal) or passive (reflect light); data is recorded on videotape or digitally;
• video systems – segments digitised
• electromagnetic sensors
2-dimensional vs 3-dimensional:
• out of plane motion
• camera records a 2-d image – computer reconstructs 3-d co-ordinates from several cameras.
Skin and footwear movement artefact:
• markers placed on skin or externally on footwear may not necessarily reflect movement of osseous segments
• sagittal plane motions of segments are greater, so skin movement artefact may not be a problem
• transverse plane motions of segment are smaller, so skin movement artefact may be a significant problem meaningless data
The measurement of force and pressure.
Ground reaction forces:
• measured by force plate/platform – measures changes in the magnitude and direction of the net force between the floor and foot
Joint moments and joint power:
• sometimes called link-segment analysis, as each segment is considered as a rigid body that are linked by frictionless hinges
• combines kinematic measurements, mass and centre of mass, with ground reaction force measurements to calculate net moments at joints (inverse dynamics approach)
Plantar pressure measurements: