week 1

Vocabulary flashcards covering key concepts, terms, and equipment related to video-based motion analysis in advanced biomechanics.

Motion Analysis

The quantitative study of movement using cameras and markers to measure kinematic variables such as position, velocity, and acceleration.

2D Motion Analysis

Analysis of movement in a single plane using 2D video; cheaper and simpler but prone to perspective and parallax errors.

High-speed video

Video captured at very high frame rates to resolve rapid movements and critical events.

Olympus I-Speed

A model of high-speed camera commonly used for motion capture.

Radar Gun

A device used to measure the speed of moving objects as part of motion analysis.

Electromyography (EMG)

A technique for recording electrical activity produced by skeletal muscles during contraction.

Data Filtering

The process of smoothing data to reduce noise before computing derivatives like velocity and acceleration.

Free Body Diagram

A schematic showing a body or body part with all external forces acting on it for torque/force analysis.

Joint torque

The rotational effect produced by forces acting about a joint axis.

3D Motion Analysis

Analysis of movement in three dimensions using multiple cameras to reconstruct 3D coordinates.

Vicon motion capture

A high-precision 3D motion capture system using retroreflective markers and cameras.

Quantitative biomechanics applications

Practical uses of measuring and analyzing motion data to improve performance, safety, and rehabilitation.

Calibration

Process of linking image measurements (pixels) to real-world distances using a known reference.

Scale Factor

Ratio Real-world length ÷ Pixel length used to convert pixel measurements to metric units.

Pixel

A picture element; the smallest unit of a digital image used in measurement.

Frame rate

Number of video frames captured per second, determining time-resolution of the data.

Shutter speed

Duration the camera’s shutter remains open per frame, affecting motion blur.

PAL/NTSC

Analog video standards; PAL ≈ 25 fps, NTSC ≈ 30 fps, affecting timing and frame structure.

Fields

Two interlaced halves of a frame in PAL/NTSC video; time between fields is shorter than a whole frame.

Interlacing

Method of composing frames from two fields to form a complete image.

Parallax error

Measurement error caused by apparent shift in object size/location as it moves relative to the camera.

Perspective error

Distortion arising when 3D movement is projected onto a 2D camera plane.

2D vs 3D analysis decision

Choosing between 2D or 3D motion analysis based on movement, required accuracy, and resources.

Direct Linear Transformation (DLT)

Mathematical method to compute 3D coordinates from multiple 2D camera views using calibration.

Wand calibration

3D calibration method using a wand with known points moved in view of cameras to determine geometry.

Digitising

Process of identifying landmarks (e.g., joints) in video frames and assigning coordinates in a biomechanical model.

Isokinetic dynamometry

A device that measures muscle force/torque at a constant angular velocity.

Velocity

Rate of change of displacement, calculated as Δs/Δt.

Acceleration

Rate of change of velocity, calculated as Δv/Δt.

Data smoothing

Pre-derivative data smoothing to reduce noise, using filters or splines before computing velocity/acceleration.