Basic Kinematics of Human Motion – Vocabulary

A comprehensive set of vocabulary flashcards covering key biomechanics and kinematics terms from Week 2 lecture notes.

Kinematics

The branch of biomechanics that describes motion (linear or angular) without regard to the forces causing it.

Linear Motion

Motion that occurs along a straight or curved path where all parts of an object move the same distance in the same direction at the same time.

Rectilinear Motion

Type of linear motion in which movement occurs along a straight line.

Curvilinear Motion

Type of linear motion in which movement follows a curved path.

Angular Motion

Motion that occurs when an object rotates around an internal or external axis.

General Motion

Combination of translation (linear) and rotation (angular) commonly seen in human movement.

Anatomical Reference Position

Standard starting posture: standing erect, feet together, arms at sides, palms facing forward.

Superior

Toward the head or upper part of a structure.

Inferior

Away from the head; toward the lower part of a structure.

Anterior

Toward the front of the body.

Posterior

Toward the back of the body.

Medial

Closer to the midline of the body.

Lateral

Farther from the midline of the body.

Proximal

Closer to the point of attachment to the trunk.

Distal

Farther from the point of attachment to the trunk.

Superficial

Closer to or on the body surface.

Deep

Farther from the body surface; more internal.

Sagittal Plane

Cardinal plane that divides the body into left and right halves; forward-backward movements occur here.

Frontal (Coronal) Plane

Cardinal plane dividing the body into front and back halves; lateral movements occur here.

Transverse Plane

Cardinal plane dividing the body into upper and lower halves; rotational movements occur here.

Mediolateral (Frontal) Axis

Imaginary line around which sagittal-plane rotations occur.

Anteroposterior (Sagittal) Axis

Imaginary line around which frontal-plane rotations occur.

Longitudinal Axis

Imaginary vertical line around which transverse-plane rotations occur.

Cartesian Coordinate System

Spatial reference system using perpendicular x, y (and z) axes to define positions in 2-D or 3-D space.

Distance

Scalar quantity describing total path length travelled.

Displacement

Vector quantity describing straight-line change in position from start to finish.

Speed

Scalar rate of motion, calculated as distance divided by time.

Velocity

Vector rate of motion, calculated as displacement divided by time, includes direction.

Acceleration

Rate of change of velocity with respect to time.

Average Velocity

Velocity computed over a designated, finite time interval.

Instantaneous Velocity

Velocity at a specific instant in time; mathematically the slope of the tangent to a position-time curve.

Relative Angle

Angle formed between two adjoining body segments (e.g., knee joint angle).

Absolute Angle

Angle of a single body segment relative to a fixed horizontal or vertical reference.

Angular Distance

The total angular path travelled, regardless of direction.

Angular Displacement

Change in angular position, measured as the difference between initial and final orientations.

Angular Speed

Scalar rate of angular motion; angular distance per unit time.

Angular Velocity

Vector rate of angular motion; angular displacement per unit time (deg·s⁻¹, rad·s⁻¹, rev·s⁻¹).

Angular Acceleration

Rate at which angular velocity changes with time.

Right-Hand Rule

Convention for determining the direction of angular motion vectors: curl fingers in rotation direction; extended thumb gives vector direction.

Radius of Rotation

Distance from the axis of rotation to a point on the rotating body.

Tangential Acceleration

Component of linear acceleration tangent to the path, representing change in linear speed (aₜ = r·α).

Radial (Centripetal) Acceleration

Component of linear acceleration directed toward the center of curvature, representing change in direction (aᵣ = v² / r).

Cinematography/Videography

Technique of recording motion pictures (e.g., 30 fps) for kinematic analysis.

Active Marker System

Motion-capture system using light-emitting diodes (LEDs) as tracked markers (e.g., OptoTrak).

Passive Marker System

Motion-capture system using reflective markers tracked by infrared cameras (e.g., Vicon).

Digitizing

Process of converting video images into numerical coordinate data for kinematic analysis.