Angular Kinematics of Human Movement

Prepared By:

Hazrat Bilal MalakandiDPT (IPM&R, KMU)

Relative versus Absolute Angles

Relative angle:• Angle of a joint formed between the

longitudinal axes of adjacent body segments• Anatomical reference position

Absolute angle:• Horizontal reference• Vertical reference

Tools for Measuring Body Angles

Goniometer:• A goniometer is a device used in physical therapy to

measure the range of motion around a joint in the body. The term goniometry is derived from two Greek words, gonia, meaning angle, and metron, meaning measure

• One arm fixed to protractor at 00

• Other arm free to rotate• Center of goniometer over joint center• Arms aligned over longitudinal axes

Electrogoniometer (elgon): • a device for measuring angles (usually joint

angles) directly, giving an electrical output (often interfaced to a computer).

Inclinometers:

• An inclinometer or clinometer is an instrument for measuring angles of slope (or tilt), elevation or depression of an object.

Instant Center of Rotation

• The instant center of rotation, also called instantaneous center or instant center, is the point in a body undergoing planar movement that has zero velocity at a particular instant of time

Angular Kinematic RelationshipsAngular Distance & Displacement

• Assessed as difference of initial & final positions– Counterclockwise is positive– Clockwise is negative

• Measured in– Degrees, radians, or revolutions

Angular Kinematic Relationships Angular Speed & Velocity

Angular speed = angular distance / = /change in time t

Angular velocity = angular displacement/ = / change in time t

Units: deg/s, rad/s, rev/s, & rpm

Angular Kinematic Relationships Angular Acceleration

Angular acceleration = change in angular velocity/ change in time

= /t

Units – deg/s2, rad/s2, & rev/s2

Relationship Between Linear and Angular Motion

s = r

Radius of rotation:• Linear distance & radius of rotation same units• Angular distance in radians

Linear and Angular Velocity

V = r m/s = (m) (rad/s)