Biomechanical Biomechanical Aspects of Workplace Aspects of Workplace DesignDesign

Presented By-Pushkar GhatoleRoll no.56

Workplace : A closer look Workplace : A closer look

Factors Contributing To Factors Contributing To Problems In Work TasksProblems In Work Tasks

• Awkward postures• Repetitive motions• Forceful exertions• Pressure points (e.g., local contact stress)• Vibration• Miscellaneous

• Environmental Factors• The duration of tasks• The length and frequency of muscle relaxation breaks• Activities outside workplace• Personal Factors

WHY?

WHY?

Awkward PosturesAwkward Postures• Posture affects which muscle groups are active during physical activity

• Awkward postures can make work tasks more physically demanding, by increasing the exertion

ReachinReachingg

TwistingTwistingBendingBendingWorking Working overheaoverhea

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Holding of Holding of fixedfixed

positionspositionsPinch gripsPinch gripsVisual EffortVisual Effort

Repetitive motionsRepetitive motions

• In repetitive work the same types of motions are performed over and over again using the same muscles, tendons, or joints

• The amount of repetition can be affected by:• The pace of work• The recovery time provided• The amount of variety in work tasks

Forceful exertionsForceful exertions

• Exerting large amounts of force can result in fatigue and physical damage to the body

• The amount of force exerted depends on:

• Load shape, weight, dimensions, and bulkiness• Grip type, position, and friction characteristics• Amount of effort required to start and stop the load when moving it• Length of time continuous force is applied by the muscles • Number of times the load is handled per hour or work shift• Amount of associated vibration• Body posture used• Resistance associated with moving the load • Duration of the task over the work shift• Environmental temperature• Amount of rotational force (e.g., torque from tools or equipment

Pressure points Pressure points

• Sides of the fingers• Palms• Wrists• Forearms• Elbows• Knees

VibrationVibration

• Fatigue• Pain• Numbness• Tingling• Increased sensitivity to cold •Decreased sensitivity to touch in the fingers hands and arms.

MiscellaneousMiscellaneous

Biomechanical Aspects of Biomechanical Aspects of Workplace DesignWorkplace Design

Prof. Don Chaffin

The University of MichiganCenter for Ergonomics

Computerized biomechanical models of the human musculoskeletal system

This knowledge can help ergonomists:

1.Evaluate the extent to which existing jobs place physical demands on the workers.

2. Simulate alternative work methods and determine potential reduction in physical demands.

3. Provide a basis for employee selection and placement procedures.

BackgroundBackground

Factors determining workplace Factors determining workplace layoutlayout

• Shoulder-dependent Overhead Reach limitations

• Shoulder and arm Dependent Forward reach Limits

• Neck/Head posture work limitations

• Torso postural Considerations in workplace height limitations

Shoulder-dependent Overhead Reach Shoulder-dependent Overhead Reach limitationslimitations

• Hands should not have to reach frequently or be held for sustained periods above the shoulder

• Shoulder flexed and held above 900 causes muscle fatigue even in no load

• For tossing ,the receiving container should be placed low to minimize arm elevations , above 500 from vertical

Shoulder-dependent Overhead Reach Shoulder-dependent Overhead Reach limitationslimitations

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Expected time to reach significant shoulder muscle fatigue for different FORWARD ARM REACH POSTURES (Chaffin, 1973).

When reaching forward, a load of 56N held in hands will create a load moment at shoulder , for average female and 115 N for average male

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Hand orientation + Arm Postures

- Design of hand tools ,tote boxes handles, control on machines

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Shoulder and arm Dependent Forward reach Shoulder and arm Dependent Forward reach LimitsLimits

Forearm rotation strengths

Neck/Head posture work limitationsNeck/Head posture work limitations

The requirement of work postures with the neck flexed forward can occur because of a combination of:

•The seat height being too high

•The seat placement being too far back from the work area

•A workbench or table being too low

•The visual demands of the task requiring a specific eye location •( e.g. to look into a near-vertical microscope)

•Maximum - 300

Torso postural Considerations in workplace Torso postural Considerations in workplace height limitationsheight limitations

• At 300 inclination of torso from the erect posture, the load moment is 50% of its maximum value achieved at 900.

• Prolonged forward stooped posture Low height of the working table.Back pain

• Back muscle endurance times in various stooped postures decreased when posture required more than about 30% of isometric strength.

• Most men and 80-90% women can maintain 200 stooped posture during a day.

The final designThe final design Work area 5cm below the elbow when standing or seated in

an erect posture.

Adequate clearance for necessary elbow and forearm motions

Requires little stooping or shoulder rotations

Workbench height adjustable between 94 and 115 cm

Heavy objects to be kept at 75cm. – Concept is to provide the location of the load close to the body of operator.

The final designThe final design

The final designThe final design

There is no single ‘Correct’ PostureThere is no single ‘Correct’ Posture

Adjustable ChairAdjustable Chair

The Computer ProblemThe Computer Problem

ReferencesReferences

Control and Display Design/Anthropometry Lecture Outline

Easy Ergonomics, A Practical Approach for Improving the Workplace developed by the Education and Training Unit, Cal/OSHA Consultation Service, California Department of Industrial Relations

How to identify, control, and reduce musculoskeletal disorders in your workplace! -Presented by the Public Education Section Department of Business and Consumer Business Oregon OSHA

Practical solutions for a safer workplace- Prepared by WISHA Services Division Washington State Department of Labor and Industries