Introduction to Ergonomics

Engineering Definitions Process: Problem symptom or need Problem Definition, Statement of Desired Outcome Analysis (Experimentation?) Synthesis of Alternative Solutions Decision (Selection)

Process Example What are the design considerations for a prosthetic Leg?

Ergonomics - Introduction Derived from the Greek “nomos” – natural laws, “ergon” – work Definition – discipline that uses knowledge of human abilities to design systems, jobs, tools, and products for the safe and efficient execution of work. Ergonomic Objective: Worker Capacity <= Job Demands

Ergonomics - Introduction Worker Capacity <= Job Demands Methods: Workplace and Equipment Design Tool Design Design of Work Methods Matching Capabilities and Limitations of Worker

Ergonomics – Introduction Why Important? Specialization / Automation Diversity of Workforce / Labor Laws Gender Aging Population Injured, Disabled workers Increase Productivity / Competitive Advantage Prevent Injury / Reduce workers Comp Costs Societal Quality of Life

Ergonomics and Physiology Relevant Subject Areas Muscular Nervous Circulatory Digestive Psychosocial Cognitive Sensory

Ergonomics and Physics Force Regularly exerted ON the body and BY the body F=ma Acts in a linear direction Muscles generate force

Ergonomics and Physics Torque M=F*D Acts as a moment about a fixed point Muscles in conjunction with tendons, joins, and ligaments generate torque.

Ergonomics and Physics Pressure Imparted BY the body and ON the body P=F/A Examples

Occupational Injury Difference between Ergonomics and Safety? Cumulative Trauma Disorders (CTD) Definition: Bodily injury associated with repeated biomechanical stress over time.

Occupational Injury Risk Factors for Cumulative Trauma Disorders

Cumulative Trauma Disorders Bursitis Tendonitis Tenosynovitis Tendon injury involving the synovial sheath, caused when excessive amounts of synovial fluid are created due to extreme repetition. Sheath becomes swollen or painful.

Cumulative Trauma Disorders De Quervain’s Disease Tenosynovitis in the tendons at the base of the thumb. Finkelstein Test

Cumulative Trauma Disorders Trigger Finger (Flexor Tendonitis) Tendon swelling interferes with the normal movement of the tendons through the synovial sheath and can cause the finger to click, catch, or lock in position

Cumulative Trauma Disorders Carpal Tunnel Syndrome Impaired nervous function in the first three digits manifested as numbness, tingling, pain, and loss of dexterity. Median nerve inside the wrist becomes compressed due to inflammation or thickening of adjacent tendon sheaths. Inflammation may be caused by overexertion or repeated unsafe wrist orientations.

Tool Design Guidelines Improper Tool Design May Cause: Increased grip forces (CTD) Unwanted postures (CTD) Acute Trauma (Burns, cuts, lacerations, abrasions, fractures, strains, sprains, dislocations, etc.) Reduced Productivity

Tool Design Guidelines Situations to avoid Sustained Ulnar/Radial Wrist deviation Excessive or repeated flexion/extension of hand and wrist Excessive force Impact shocks Tissue compression from sharp edges or misdirected forces Ischemia – obstruction of blood flow to the tissues and eventual numbness or tingling

Tool Design Guidelines Types of Grip Power Precision Design for Population Gender Left/Right Handedness

Tool Design Guidelines Handle Diameter Length Shape Surface (material) Angulation Grip Span Weight

Examples Pliers Knives Scissors

Engineering Design Constraints Example: The Vibration Dilemma

The Future Workplace and Equipment Design