Humans have cognitive and physical capacities and limitations. Ergonomic principles — the science of work — take human capacities and limitations into account to design work to optimize human performance as well as recognize when we are pushing our bodies into dangerous situations that can result in serious injury.

Pramila Kalaga, Ergonomics Specialist at Nebraska Medical Center in Omaha, says ergonomic principles apply to all types of work and work environments.

“Some common principles include avoid working in awkward posture such as stooping over for long periods of time or twisting at the same time you bend over,” she says. “If you’re sitting while you work, be sure to get up at least every 60 minutes and move to reduce fatigue and discomfort.”

Additional ergonomic guidelines include avoiding putting excessive force on the spine by activities such as lifting, carrying or moving heavy objects/materials without the use of mechanical aids. 

“Injuries to the back and spine are some of the most common problems that occur when heavy work is involved,” Kalaga says. “Many people believe that using good body mechanics and fitness will protect them if they’re working with heavy components. However, once a load exceeds a certain point, good body mechanics and fitness may not be sufficient to prevent injury to the intervertebral discs of the spine. People may sometimes exceed safe limits when handling heavy materials, and not experience immediate results. That doesn’t mean there was no injury to the back. It just may not show up for a while.”

Kalaga notes that injury to the spine is often cumulative. Accelerated wear and tear injuries can accumulate to the spinal discs over time. Wear and tear on the back and spine can occur over a period of weeks, months or years. Often, by the time an individual recognizes an issue with the back or spine, the damage has been done.

“Our soft tissues such as muscles will give us feedback,” Kalaga says. “However, we don’t get good feedback from the intervertebral discs. If a muscle is strained, and muscles typically have good blood supply, the muscle will heal and a person feels good as new.”

If there’s excessive mechanical loading on intervertebral discs, with micro-factures to the vertebral endplates, a person may not necessarily have direct feedback from the injury. The micro-fractures to the vertebral endplates heal, forming scar tissue, and blood doesn’t flow well through scar tissue, contributing to further disc degeneration. Repeated excessive pressure or mechanical loading on the spinal discs can accelerate disc degeneration. If muscles are giving feedback that the load being lifted is very heavy, the person may be impacting more than muscles. They may be putting undue stress on spinal discs.

While physical fitness will increase the threshold for injury and good body mechanics also help, this combination will not be sufficient to prevent injury if excessive mechanical loading occurs on a routine basis. 

“Ideally, you would combine work design that takes human capacities into account along with physical fitness and good body mechanics,” Kalaga says. “Also keep in mind that ergonomic adjustments to the work design, sometimes relatively minor changes, can make it easier to use optimal body mechanics, reduce stress on the body and facilitate better work performance.” 

Additional lifting principles are available at this Occupational Safety and Health Administration (OSHA) site: https://www.osha.gov/ergonomics.

Funding for this educational article comes from the Central States Center for Agricultural Safety and Health and the University of Nebraska Medical Center.