biomechanical aspects of workplace design
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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
dd
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