Nelson & Associates :: Manual Lifting & Materials Handling :: Landmark Manual Lifting Standards

Basic Elements of Manual Materials Handling

Low back pain was one of the major concerns of Bernardino Ramazzini, "the founder of occupational medicine," when he published his works in the late 1600's. Throughout this century, the manual handling of objects has accounted for 20-25% of all occupational injuries and has exceeded motor vehicle accidents (and all other single causes) as a cause of lost work time and associated monetary costs.

In 1997, the U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health (NIOSH) published “Musculoskeletal Disorders and Workplace Factors – A Critical Review of Epidemiological Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back.” Within, it was noted that the Bureau of Labor Statistics (BLS) Annual Survey of Occupational Injuries and Illnesses for 1994 revealed about 705,800 lost workday cases (32% of the total) were the result of overexertion or repetitive motion. Specifically, 367,424 injuries due to overexertion in lifting (65% affected the back); 93,325 injuries due to overexertion in pushing and pulling objects (52% affected the back); 68,992 injuries due to overexertion in holding, carrying, or turning objects (58% affecting the back), with the total across these categories affecting the shoulder determined to be 47,861.

This publication (NIOSH, 1997) provided evidence regarding the relationship between low-back disorder and (1) heavy physical work, and (2) awkward (bending and twisting) postures, and strong evidence regarding the relationship between low-back disorders and (3) work-related lifting and forceful movements.

Today it is recognized that the most effective way to control back injuries is through proper design and evaluation of the workplace. Instructions to "lift with your legs and not your back" and "keep your back straight" are of limited value without workplace controls. If the squat-lift method necessitates that the load be lifted further away from the body (in front of the knees), it has been shown that forces on the erector spinae muscles and the lumbosacral disc can be as much as 50 % higher when using such a historically recommended squat posture compared to a stooped posture. Employers should also know that it is of little value to tell workers to "ask for help when you feel you need it" because a dangerous lift may "appear" or "feel" acceptable to the worker until an injury has occurred.

Milestones in the Analysis of Manual Lifting Tasks and the Establishment of Weight Limits

  • U.S. Department of Labor, Bulletin No. 11 – Guide to the Prevention of Weight Lifting Injuries (1940s)
  • NIOSH Work Practices Guide for Manual Lifting (1981)
  • ASTM F-1166, Standard Practice for Human Engineering Design for Marine Systems (1988, 2007)
  • The "Snook" Tables (1978, 1980, 1991)
  • The Revised NIOSH Equation (1993)
  • Liberty Mutual Manual Materials Handling Guidelines (2004)
  • American Bureau of Shipping, Guidance Notes for the Application of Ergonomics to Marine Systems (2003)
  • American Conference of Governmental Industrial Hygienists (ACGIH), TLV for Lifting (2005)

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