Basic Biomechanics

1. Angular Kinematics of Human
Movement
Prepared By:
Hazrat Bilal Malakandi
DPT (IPM&R, KMU)

2. 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

4. 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

6. Electrogoniometer (elgon):
• a device for measuring angles (usually joint
angles) directly, giving an electrical output
(often interfaced to a computer).

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

8. 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

9. Angular Kinematic Relationships
Angular Distance & Displacement
• Assessed as difference of initial & final
positions
– Counterclockwise is positive
– Clockwise is negative
• Measured in
– Degrees, radians, or revolutions

10. 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

11. Angular Kinematic Relationships
Angular Acceleration
Angular acceleration = change in angular
velocity/ change in time
 =  /t
Units – deg/s2, rad/s2, & rev/s2

12. Relationship Between
Linear and Angular Motion
s = r
Radius of rotation:
• Linear distance & radius of rotation same units
• Angular distance in radians

13. Linear and Angular Velocity
V = r m/s = (m) (rad/s)