Ergo Biomech 2008

ERGONOMICS DR. SITI ZAWIAH MD. DAWAL DEPT. OF ENGINEERING DESIGN AND MANUFACTURE UNIVERSITY OF MALAYA

ERGONOMICS and BIOMECHANICS

Copyright @ 2008 by ERGO

Introduction Bio- life or way of life in Greek Mechanics – branch of science – deals with forces and effect of forces…….

Three disciplines Mechanics of rigid body Mechanics of solid deformable bodies Fluid mechanics

Mechanics- Forces and Motion Description and analysis of motion -kinematics Description and analysis of forces – kinetics Description and analysis of forces tend to cause motion -statics

Kinematic concepts for analyzing human motion

The Skeleton

General Functions Gives the body its basic shape and provides a strong , protective and supporting framework for all other systems of the body. With regards to movement the bones of the skeleton act as a levers operated by the skeletal muscles.

Mechanical Functions At birth – 270 bones Adults – 206 bones 4)Acts as a supporting framework for the rest of the body 5)Acts as a lever system – muscle 6)Protect certain organs

Anatomical Reference Position Is the reference position or starting place when movement terms are defined. Is an erect standing position with feet just slightly separated and the arms hanging relaxed at the sides with the palms of the hands facing forward.

Anatomical Reference Planes Median Plane or Sagittal plane – vertical plane that divide the body - left and right portions. Coronal plane or Frontial plane – vertical plane perpendicular to median plane. ( anterior and posterior) Tranverse Plane – horizontal plane perpendicular to both median and coronal planes.

Types of movements See handouts

Newton’s 1 Law of Motion st

A body which is at rest will remain at rest unless some external force is applied to it and a body which is moving at a constant speed in a straight line will continue to do so unless some external force is applied to it.

Newton’s 2 law of Motion nd

Force = mass x acceleration F=mxa The relationship between force, the resulting motion of a body and the properties of the body itself.

Newton’s 3 Law of motion rd

To every action force there is always opposed an equal reaction force or The mutual action forces of two bodies upon each other are always equal and oppositely directed.

Moment of Force = W x distance X1 Where W is the magnitude of the gravitational force e.g. weight of the boot and X1 is the perpendicular distance

Tutorial How would you represent the line of

gravity of the patient in each of the diagrams given. (approximate position)

@ 2008 by ERGO Copyright Copyright @ 2008 by ERGO

Centre of Gravity The centre of gravity (C of G) of an object is the point at which all of the weight of the object may be considered to be concentrated and about which the object ( in theory) exactly balance.

Machines and mechanism Rehabilitation machines are devices that have been developed to provide specific movements for limbs or joints or to provide specific resistance to muscle action

Mechanism Mechanism such as lever used in machines to transform motion and /or force into a desired output.

Lever A lever is a rigid beam pivoted at a point known as the fulcrum. There are three classes of lever   

- First order lever - Second order lever - Third order lever

Inclined Plane Inclined plane is a good example of a method used since ancient times to raise heavy loads with a relatively small effort.

Tutorial 1 2) Refer to the 1st Q comment on the stability of the subject in each position. 3) Refer to figure 2, assume that the combined weight of a patient and a wheel chair is 800N and the therapist is required to push the wheelchair up a ramp that has a slope of 1 in 10. Calculate the minimum force that the therapist must apply to push the chair